📋 Key Information Summary
- Acute skin eruptions in Australian primary care require a systematic diagnostic approach using morphology, distribution, onset timing, and associated symptoms to narrow the differential.
- Urticaria affects ~20% of Australians in their lifetime; acute urticaria (<6 weeks) is most commonly idiopathic or drug/food-related and responds to second-generation H₁ antihistamines as first-line therapy.
- Drug eruptions account for ~2–3% of all dermatology consultations; the most common pattern is a widespread morbilliform (exanthematous) eruption appearing 7–14 days after drug initiation.
- Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening emergencies (mortality 10–50%) requiring immediate cessation of the causative drug and transfer to a burns/ICU unit.
- Key high-risk medications for SJS/TEN in Australia include carbamazepine, allopurinol, sulfonamides, lamotrigine, and NSAIDs; HLA-B*5701 and HLA-B*1502 testing is available on Medicare (MBS item 71157).
- Fixed drug eruptions recur at the same anatomical site on re-exposure and typically present as a solitary dusky erythematous plaque; common culprits include paracetamol, NSAIDs, tetracyclines, and trimethoprim-sulfamethoxazole.
- Pityriasis rosea is a self-limiting eruption often preceded by a herald patch; it follows skin lines in a "Christmas-tree" pattern on the trunk and resolves spontaneously within 6–8 weeks.
- Guttate psoriasis presents as numerous small (0.5–1.5 cm) salmon-pink scaly papules, typically 1–3 weeks after streptococcal pharyngitis; throat swab and antistreptolysin O titre (ASOT) should be performed.
- Secondary syphilis must be considered in any widespread papulosquamous or palmoplantar eruption, especially in men who have sex with men (MSM), Aboriginal and Torres Strait Islander communities in remote areas, and people with HIV.
- The "great imitator" — secondary syphilis can mimic pityriasis rosea, guttate psoriasis, drug eruption, and viral exanthem; always order syphilis serology (RPR/VDRL + TPPA/TPHA) in unexplained widespread eruptions.
- Primary HIV eruption (acute retroviral syndrome) presents 2–4 weeks post-exposure with a diffuse maculopapular rash, fever, lymphadenopathy, pharyngitis, and mucosal ulcers; fourth-generation HIV Ag/Ab test is essential in at-risk patients.
- Aboriginal and Torres Strait Islander populations have significantly higher rates of syphilis (especially in northern and central Australia); the Australian Syphilis Action Plan mandates opportunistic testing in antenatal and sexual health settings.
- All patients with suspected drug eruptions should be documented on the Australian Adverse Drug Reaction Reporting System (via TGA) and flagged in My Health Record.
Introduction & Australian Epidemiology
Acute skin eruptions are among the most common presentations in Australian general practice, accounting for approximately 10–15% of all consultations. They span a broad differential — from benign self-limiting conditions such as pityriasis rosea to life-threatening emergencies such as Stevens–Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and acute HIV seroconversion. Accurate diagnosis hinges on a structured approach integrating lesion morphology, distribution, timeline of onset, systemic features, and exposure history.
In Australia, several epidemiological factors shape the landscape of acute skin eruptions:
- Polypharmacy and an ageing population: The prevalence of adverse drug reactions increases with the number of concurrent medications. Older Australians (≥65 years) take a median of five prescription medications, placing them at elevated risk for drug eruptions.
- High UV exposure: Australia has the highest rate of skin cancer globally; while this primarily drives melanoma and non-melanoma skin cancer, UV-triggered eruptions (polymorphic light eruption, photoallergic drug reactions) are also prevalent.
- Infectious disease burden: Syphilis notifications have increased markedly since 2010, particularly among Aboriginal and Torres Strait Islander communities in northern Australia and among MSM nationally. The 2017–2024 syphilis outbreak prompted a national action plan.
- Immunisation landscape: Widespread MMR vaccination has reduced measles and rubella exanthems, but vaccine-related rashes (e.g., MMR at 7–12 days post-vaccine) remain relevant.
- HLA pharmacogenomics: Australia has pioneered HLA-B*5701 screening for abacavir hypersensitivity and HLA-B*1502 screening for carbamazepine-related SJS/TEN; both are available on the Medicare Benefits Schedule.
This article provides a systematic framework for evaluating and managing acute skin eruptions in Australian primary and secondary care, with emphasis on conditions most commonly encountered: urticaria, drug eruptions, pityriasis rosea, guttate psoriasis, secondary syphilis, and primary HIV eruption.
Acute Skin Eruptions Diagnostic Model
A structured diagnostic approach is essential when evaluating acute skin eruptions. The following mnemonic — MORPH–DASH — provides a systematic framework for Australian clinicians.
1
M — Morphology
Describe the primary lesion: macule, papule, plaque, vesicle, bulla, wheal, pustule, or target. Note secondary changes (scale, crust, erosion). Biopsy if diagnosis uncertain after 2–4 weeks.
2
O — Onset & Timing
Sudden (<24 h) suggests urticaria, anaphylaxis, or viral exanthem. Gradual (days–weeks) suggests drug eruption, pityriasis rosea, or secondary syphilis. Temporal relation to new medications (7–21 days for first exposure, 1–3 days for re-exposure).
3
R — Region / Distribution
Trunk-predominant: pityriasis rosea, viral exanthem, drug eruption. Palmoplantar: secondary syphilis, hand-foot-mouth disease, erythema multiforme. Photo-distributed: polymorphic light eruption, photoallergic drug reaction. Mucosal involvement: SJS/TEN, erythema multiforme major, primary HIV.
4
P — Palpation & Feel
Wheals are transient, raised, and compressible (urticaria). Papulosquamous lesions have adherent scale (psoriasis, syphilis). Flaccid blisters with positive Nikolsky sign (SJS/TEN). Indurated plaques (fixed drug eruption). Dusky/violaceous hue (fixed drug eruption, lichenoid drug eruption).
5
D — Drug & Exposure History
Meticulous review of all medications (prescription, OTC, complementary) introduced in the preceding 1–3 weeks. Recent infections (streptococcal pharyngitis → guttate psoriasis). Sexual history (syphilis, HIV). Travel history. Vaccination history. Dietary exposures.
6
A — Associated Symptoms
Fever + rash + mucositis = SJS/TEN or viral haemorrhagic fever (consider travel). Pruritus without systemic symptoms = urticaria or eczematous drug eruption. Arthralgia + rash = secondary syphilis, viral arthritis, serum sickness. Lymphadenopathy + rash = secondary syphilis, HIV, EBV, lymphoma.
7
S — Systemic & Safety Red Flags
Immediate transfer to ED if: blistering/epidermal detachment >1 BSA, mucosal erosions, fever >38.5°C with widespread erythema, facial oedema with tongue/lip swelling, or haemodynamic instability.
8
H — Histology & Investigations
Skin biopsy (punch or shave) for uncertain diagnoses. Serological testing (syphilis RPR/VDRL + TPPA, HIV Ag/Ab). FBC, LFTs, EUC, CRP for systemic assessment. Throat swab and ASOT if post-streptococcal aetiology suspected.
Red-flag features requiring immediate escalation: Widespread blistering or skin detachment, mucosal erosions (oral, ocular, genital), high fever with erythroderma, facial/laryngeal oedema, or haemodynamic compromise. Transfer to the nearest emergency department immediately. Do not wait for investigation results.
| Pattern | Key Morphology | Typical Distribution | Timing | Top Differential |
|---|---|---|---|---|
| Transient wheals | Erythematous, raised, pruritic, each lasting <24 h | Any site; often generalised | Minutes to hours | Urticaria |
| Morbilliform | Confluent macules/papules, blanching | Trunk → limbs; spares palms/soles | 7–14 days after drug | Drug eruption, viral exanthem |
| Herald patch + secondary | Oval scaly plaques following skin lines | Trunk ("Christmas tree") | Days to weeks | Pityriasis rosea |
| Small scaly papules | Salmon-pink, 0.5–1.5 cm, fine scale | Trunk, proximal limbs | 1–3 weeks post-pharyngitis | Guttate psoriasis |
| Papulosquamous + palmoplantar | Copper-coloured papules/plaques | Palms, soles, trunk, mucous patches | Weeks–months post-primary chancre | Secondary syphilis |
| Target lesions + blistering | Atypical targets, flaccid blisters, positive Nikolsky | Trunk → generalised; mucosae | 7–21 days after drug | SJS / TEN |
Urticaria & Drug Reactions
Urticaria
Urticaria affects approximately 20% of the Australian population at some point in their lifetime. Acute urticaria (duration <6 weeks) is characterised by transient, pruritic wheals (<24 hours per individual lesion) and is most commonly triggered by infections, medications (especially NSAIDs and antibiotics), food allergens, or physical stimuli. Chronic urticaria (≥6 weeks) has a point prevalence of ~1% and may be spontaneous or inducible.
Angioedema without wheals: Consider hereditary angioedema (C1 esterase inhibitor deficiency) or ACE inhibitor–induced angioedema. Do not treat as simple urticaria. C1-INH levels and C4 complement are available through most Australian pathology providers (Medicare-rebatable).
First-Line Management — Acute Urticaria
Cetirizine
Zyrtec® · Generic · 2nd-gen H₁ antihistamine
Adult dose
10 mg PO once daily; up to 40 mg/day (4× dose) in refractory chronic urticaria per ASCIA
Paediatric dose
2–5 years: 2.5 mg PO once daily (5 mg if ≥30 kg); 6–11 years: 5–10 mg PO once daily
Renal adjustment
eGFR 30–50: reduce dose by 50%; eGFR <30: reduce dose by 50% and increase dosing interval
PBS status
✔ PBS General Benefit
Loratadine
Claratyne® · Generic · 2nd-gen H₁ antihistamine
Adult dose
10 mg PO once daily; up to 40 mg/day in refractory cases
Paediatric dose
2–5 years: 5 mg PO once daily; 6–11 years: 10 mg PO once daily
Renal adjustment
No adjustment required
PBS status
✔ PBS General Benefit
Fexofenadine
Telfast® · Generic · 2nd-gen H₁ antihistamine
Adult dose
180 mg PO once daily; up to 720 mg/day in refractory chronic urticaria
Paediatric dose
6–11 years: 30 mg PO twice daily (or 60 mg once daily)
Renal adjustment
eGFR <30: 60 mg once daily
PBS status
✔ PBS General Benefit
Refractory Acute / Chronic Urticaria
If symptom control is inadequate after 2–4 weeks at licensed dose, up-dose to 4× the standard dose of the chosen second-generation antihistamine (as per ASCIA/EAACI guidelines). Add short course of prednisolone (0.5–1 mg/kg/day, maximum 50 mg, for 3–7 days) for severe acute flares. For chronic spontaneous urticaria (CSU) refractory to high-dose antihistamines, refer to an immunologist/allergist for consideration of omalizumab (Xolair®), which is available on the PBS via authority prescription for CSU.
Prednisolone
Panafcortelone® · Generic · Corticosteroid
Adult dose
0.5–1 mg/kg/day PO (max 50 mg), taper over 3–7 days
Paediatric dose
1–2 mg/kg/day PO (max 40 mg), taper over 3–7 days
Renal adjustment
No adjustment required
PBS status
✔ PBS General Benefit
Omalizumab
Xolair® · Anti-IgE monoclonal antibody
Adult dose
150–300 mg SC every 4 weeks (dose based on body weight and IgE level)
Paediatric dose
≥12 years: as per adult dosing table
Renal adjustment
No adjustment required
PBS status
⚑ PBS Authority Required — for CSU refractory to ≥3 months high-dose antihistamines
Drug Eruptions
Adverse cutaneous drug reactions (ACDR) occur in 2–3% of hospitalised patients and are one of the most frequent reasons for dermatology referral. The pattern of drug eruption is determined by the medication, the patient's immune response, and pharmacogenomic risk factors.
Mild
Morbilliform (Exanthematous) Drug Eruption
Most common pattern (~75% of drug eruptions). Symmetric maculopapular eruption starting on trunk, spreading centrifugally. No mucosal involvement, no blistering. Mild pruritus. Onset 7–14 days after first exposure, 1–3 days on re-exposure.
Setting: GP surgery — outpatient management
Moderate
Urticarial / DRESS / Fixed Drug Eruption
DRESS (drug reaction with eosinophilia and systemic symptoms): onset 2–6 weeks, facial oedema, eosinophilia, hepatitis, renal impairment, lymphadenopathy. Fixed drug eruption: solitary dusky erythematous plaque recurring at same site. Requires bloods and possible biopsy.
Setting: Urgent GP review ± ED if systemic features
Severe
SJS / TEN / Acute Generalised Exanthematous Pustulosis (AGEP)
SJS: <10% BSA epidermal detachment + mucosal erosions. TEN: >30% BSA. AGEP: acute onset sterile pustules on erythematous base, fever, neutrophilia. Nikolsky sign positive. Immediate life-threatening emergency.
Setting: Immediate ED transfer → Burns/ICU
High-Risk Medications for SJS/TEN in Australia
| Medication | HLA Association | Screening Available | MBS Item |
|---|---|---|---|
| Carbamazepine | HLA-B*1502 (Southeast Asian, Han Chinese) | Yes — pre-treatment recommended in at-risk populations | 71157 |
| Allopurinol | HLA-B*5801 (Korean, Han Chinese, Thai, European) | Yes — recommended in high-risk populations | 71157 |
| Abacavir | HLA-B*5701 | Yes — mandatory before initiation | 71157 |
| Lamotrigine | HLA-B*1502 (Southeast Asian) | Yes — recommended in at-risk populations | 71157 |
| Sulfonamides (incl. cotrimoxazole) | No specific HLA association | N/A | N/A |
| Nevirapine | HLA-DRB1*0101 | Yes — CD4 count and HLA testing recommended | 71157 |
Stevens–Johnson Syndrome / Toxic Epidermal Necrolysis — Emergency Management
SJS/TEN is a medical emergency. Mortality: SJS ~10%, TEN ~30–50% (SCORTEN-based). If blistering or mucosal erosions are present, stop ALL suspected causative medications immediately. Call 000 or arrange urgent transfer to the nearest burns/ICU centre. Do not delay for biopsy confirmation.
1
Stop causative drug
Cease all suspect medications immediately. Document in My Health Record and submit a TGA Adverse Drug Reaction report. Do NOT reintroduce the suspected drug.
2
Assess SCORTEN
Calculate SCORTEN within 24 hours and again at 72 hours. Parameters: age >40, heart rate >120, active malignancy, BSA >10%, urea >10 mmol/L, glucose >14 mmol/L, bicarbonate <20 mmol/L.
3
Transfer to burns/ICU
Patients with >10% BSA detachment or mucosal involvement require burns unit or ICU-level care. In Australia, contact your state burns service (e.g., Royal Adelaide Hospital, Royal Brisbane and Women's Hospital, Alfred Hospital).
4
Supportive care
Fluid resuscitation (Parkland formula adapted for dermatological burns). Pain management (IV opioids). Nutritional support (NGT if oral mucositis). Ophthalmology review (critical for ocular surface involvement). Temperature management. VTE prophylaxis.
5
Infection prevention
Barrier nursing. Monitor for secondary infection. Do NOT use prophylactic systemic antibiotics. Culture any suspicious wound. Skin biopsy for frozen section to confirm diagnosis if unclear.
Fixed Drug Eruption
Fixed drug eruption (FDE) presents as one or a few well-circumscribed, dusky erythematous to violaceous plaques that recur at the exact same anatomical site upon re-exposure to the causative agent. Post-inflammatory hyperpigmentation is characteristic. Commonly affected sites include the lips, genitalia, hands, and feet. Oral mucosal involvement is possible (non-pigmenting FDE variant).
- Common culprits: Paracetamol (increasingly recognised in Australia), NSAIDs (especially ibuprofen), trimethoprim-sulfamethoxazole, tetracyclines (especially doxycycline), metronidazole, and pseudoephedrine.
- Diagnosis: Clinical — based on history of recurrence at same site. Skin biopsy (if needed) shows interface dermatitis with dyskeratotic keratinocytes, pigment incontinence.
- Management: Identify and cease the causative agent. Acute episodes respond to topical corticosteroids (e.g., mometasone furoate 0.1% once daily). Extensive/mucosal FDE may require short course of prednisolone (0.5 mg/kg/day for 5–7 days). Provide written documentation of the causative drug for the patient's records and flag in My Health Record.
DRESS Syndrome
Drug reaction with eosinophilia and systemic symptoms (DRESS), also known as drug-induced hypersensitivity syndrome (DIHS), is a severe, potentially life-threatening drug reaction characterised by a prolonged latency period (2–6 weeks), widespread eruption, facial oedema, lymphadenopathy, haematological abnormalities (eosinophilia or atypical lymphocytes), and organ involvement (hepatitis most common, followed by nephritis, pneumonitis, and myocarditis).
- Common causative agents: Carbamazepine, phenytoin, allopurinol, dapsone, sulfonamides, minocycline, vancomycin, and nevirapine.
- RegiSCAR scoring: Use to confirm diagnosis (fever, lymphadenopathy, eosinophilia, atypical lymphocytes, skin involvement, organ involvement, resolution time, biopsy findings).
- Management: Discontinue causative drug. Systemic corticosteroids (prednisolone 1 mg/kg/day) with slow taper over 6–8 weeks to prevent relapse. Monitor liver function (LFTs every 48–72 h), renal function, and thyroid function (autoimmune thyroiditis may develop 1–3 months post-recovery). Referral to dermatology and immunology. Report to TGA.
- Herpesvirus reactivation: HHV-6, HHV-7, EBV, and CMV reactivation is common in DRESS and may drive flares. Consider viral PCR if clinical deterioration occurs.
Prednisolone
Panafcortelone® · Corticosteroid
DRESS dose
1 mg/kg/day PO, taper over 6–8 weeks (minimum). Monitor for relapse during taper.
Renal adjustment
No adjustment required
PBS status
✔ PBS General Benefit
Mometasone furoate
Elocon® · Topical corticosteroid
Indication
Mild–moderate fixed drug eruption — apply thin layer to affected area once daily for 7–14 days
Renal adjustment
Not applicable (topical)
PBS status
✔ PBS General Benefit
Toxic Erythema (Toxic Erythema of Chemotherapy)
Toxic erythema of chemotherapy (TEC), previously termed "palmoplantar erythrodysesthesia" or "chemotherapy-related acral erythema," is a distinct cutaneous reaction to various chemotherapeutic agents. It presents with painful erythema, oedema, and desquamation affecting the palms, soles, and intertriginous areas. Common causative agents include cytarabine, doxorubicin, capecitabine, and 5-fluorouracil. Management involves dose reduction, cooling compresses, emollients, topical corticosteroids, and supportive analgesia.
Pityriasis Rosea & Guttate Psoriasis
Pityriasis Rosea
Pityriasis rosea (PR) is a common, self-limiting papulosquamous eruption that typically affects adolescents and young adults (peak incidence 10–35 years). It is believed to be triggered by reactivation of human herpesvirus 6 (HHV-6) or HHV-7. The condition is characteristically preceded by a prodromal illness in ~50% of cases.
Clinical Features
- Herald patch: A single, oval, salmon-pink, scaly plaque (2–5 cm) appearing 1–2 weeks before the generalised eruption. Often misdiagnosed as a ringworm lesion (tinea corporis).
- Secondary eruption: Numerous smaller (0.5–2 cm) oval papules and plaques with a peripheral "collarette" of scale. Distribution follows skin tension lines on the trunk in a characteristic "Christmas-tree" pattern.
- Atypical variants: Inverse PR (face, flexures, acral sites), papular PR (in children and darker skin types — higher risk of post-inflammatory hyperpigmentation), purpuric PR, and giant PR.
- Duration: Self-resolves within 6–8 weeks (range 2–12 weeks). Recurrence rate ~2–3%.
- Pruritus: Variable; often mild, but can be moderate–severe in some patients.
Differential Diagnosis
| Condition | Key Distinguishing Features | Investigation |
|---|---|---|
| Secondary syphilis | Copper-coloured, palm/sole involvement, mucous patches, lymphadenopathy, condylomata lata | RPR/VDRL + TPPA/TPHA |
| Guttate psoriasis | Salmon-pink with thicker scale, often preceded by streptococcal infection, family history of psoriasis | Throat swab, ASOT |
| Tinea corporis | Annular with active scaly border, KOH positive | KOH mount, fungal culture |
| Nummular eczema | Coin-shaped, more eczematous (oozing/crusting), intensely pruritic | Clinical |
| Drug eruption | Temporal relation to medication, less patterned distribution | Drug history, biopsy if needed |
Always exclude secondary syphilis before diagnosing pityriasis rosea. Order RPR/VDRL and TPPA/TPHA serology in all patients with a suspected PR presentation. Syphilis rates are rising across Australia, and misdiagnosis can have devastating consequences (tertiary syphilis, congenital syphilis).
Management
- Reassurance and observation: The mainstay of treatment. PR is self-limiting. Explain the expected course (6–8 weeks) and provide written information.
- Pruritus management: Emollients, topical corticosteroids (e.g., triamcinolone acetonide 0.1% once daily to pruritic areas), and/or second-generation antihistamines (cetirizine 10 mg PO once daily).
- UV therapy: Natural sunlight exposure or narrowband UVB phototherapy (3–5 sessions/week for 2–3 weeks) may accelerate resolution. Refer to dermatology for phototherapy in persistent or severe cases.
- Oral erythromycin: Some evidence for efficacy (250 mg QID for 2 weeks) in shortening disease duration. Use only in selected, severe cases.
- Avoid: Fragranced products, harsh soaps, and hot water which may exacerbate pruritus.
Triamcinolone acetonide 0.1%
Kenac® · Topical corticosteroid (mid-potency)
Adult dose
Apply thin layer to affected areas once daily for 7–14 days
Paediatric dose
Use lowest potency effective; avoid prolonged use in children
PBS status
✔ PBS General Benefit
Guttate Psoriasis
Guttate psoriasis ("gutta" = drop) is an acute form of psoriasis characterised by numerous small (0.5–1.5 cm), salmon-pink, scaly papules predominantly affecting the trunk and proximal extremities. It accounts for approximately 2% of all psoriasis and is the most common form of psoriasis in children and young adults. A strong association exists with preceding streptococcal pharyngitis (reported in 56–97% of cases).
Pathogenesis
Beta-haemolytic Streptococcus pyogenes (Group A Streptococcus, GAS) pharyngeal infection triggers a cross-reactive immune response involving streptococcal M-protein epitopes, which activate T cells and cytokine cascades (IL-17, IL-23, TNF-α) that drive epidermal hyperproliferation in genetically susceptible individuals. Up to one-third of patients with guttate psoriasis will later develop chronic plaque psoriasis.
Investigations
- Throat swab: Culture for GAS (available via standard pathology providers; results 24–48 hours).
- Antistreptolysin O titre (ASOT): Evidence of recent streptococcal infection (rises 1–3 weeks post-infection, peaks at 3–6 weeks). Medicare-rebatable (MBS item 65750).
- Anti-DNase B: Complementary to ASOT, particularly useful when presentation is delayed >6 weeks.
- Syphilis serology: As per pityriasis rosea — RPR/VDRL + TPPA/TPHA to exclude secondary syphilis.
- Skin biopsy (rarely needed): If diagnosis uncertain — shows regular acanthosis, parakeratosis, Munro microabscesses, dilated capillaries in dermal papillae.
Management
- Treat streptococcal infection: If throat swab positive or ASOT elevated, treat with penicillin V (phenoxymethylpenicillin) 500 mg PO BD for 10 days (adults) or 250 mg PO BD for 10 days (children). Alternative: amoxicillin 500 mg PO TDS for 10 days. For penicillin allergy: azithromycin 500 mg PO day 1, then 250 mg PO days 2–5.
- Topical therapy: Emollients + moderate-potency topical corticosteroids (e.g., betamethasone dipropionate 0.05% once daily for 2–4 weeks) for symptomatic control. Vitamin D analogues (calcipotriol 50 mcg/g) as adjunct or steroid-sparing agent.
- UV phototherapy: Narrowband UVB for widespread or persistent disease. Refer to dermatology.
- Reassurance: Approximately 60–70% of cases resolve spontaneously within 2–3 months. Recurrence can occur with subsequent streptococcal infections.
Phenoxymethylpenicillin (Penicillin V)
Cilicaine VK® · Penicillin antibiotic
Adult dose
500 mg PO twice daily for 10 days
Paediatric dose
<5 years: 125 mg PO twice daily; 5–12 years: 250 mg PO twice daily; for 10 days
Renal adjustment
No adjustment required
PBS status
✔ PBS General Benefit
Betamethasone dipropionate 0.05%
Diprosone® · Potent topical corticosteroid
Adult dose
Apply thin layer once daily to affected areas for 2–4 weeks; reduce frequency once controlled
Paediatric dose
Use milder potency in children; limit duration to 1–2 weeks
PBS status
✔ PBS General Benefit
Calcipotriol
Daivonex® · Vitamin D analogue
Adult dose
Apply once or twice daily (maximum 100 g/week). Can be combined with betamethasone (Enstilar® foam or Daivobet® ointment).
Paediatric dose
≥12 years: as per adult. Avoid use >30% BSA. Monitor calcium.
PBS status
✔ PBS General Benefit
Secondary Syphilis & Primary HIV Eruption
Secondary Syphilis
Syphilis, caused by the spirochaete Treponema pallidum, has experienced a dramatic resurgence in Australia. Notifications have increased approximately 5-fold since 2010. The 2017–2024 syphilis outbreak disproportionately affected Aboriginal and Torres Strait Islander populations in northern, central, and Western Australia, as well as MSM nationally. Secondary syphilis occurs 4–10 weeks after the primary chancre and represents disseminated infection.
Secondary syphilis is the "great imitator." Always include syphilis serology in the workup of any unexplained widespread papulosquamous eruption, especially with palm/sole involvement, mucosal lesions, condylomata lata, or lymphadenopathy. A missed diagnosis can progress to tertiary syphilis (cardiovascular, neurological) or congenital syphilis.
Clinical Features of Secondary Syphilis
- Rash: Generalised, symmetric, non-pruritic, copper-coloured (or "ruddy") macules and papules. Involves the trunk, limbs, palms, and soles (palmoplantar involvement is a hallmark feature and should always prompt syphilis testing).
- Mucous patches: Painless, grey-white erosions on oral, genital, or rectal mucosa. Highly infectious.
- Condylomata lata: Flat, moist, grey-white papules/plaques in warm, moist skin folds (groin, axillae, intergluteal). Highly infectious. Differentiated from condylomata acuminata (genital warts) by their flat, smooth surface.
- Generalised lymphadenopathy: Non-tender, rubbery, mobile nodes. Often bilateral inguinal, cervical, and epitrochlear.
- Constitutional symptoms: Malaise, low-grade fever, headache, sore throat, patchy alopecia ("moth-eaten" pattern), and weight loss.
- Systemic involvement: Hepatitis (raised transaminases), nephropathy (membranous glomerulonephritis), osteitis, uveitis, meningitis.
Investigations
Essential
Syphilis serology — Non-treponemal (RPR/VDRL)
Quantitative — used for diagnosis and monitoring treatment response. Reportable in all Australian states/territories. Results available within 24–48 hours from major pathology providers (Sonic, Pathology Queensland, SA Pathology, etc.).
Essential
Syphilis serology — Treponemal (TPPA/TPHA or EIA/CIA)
Confirmatory. Most Australian labs use reverse algorithm (treponemal EIA first, confirmed by RPR). Treponemal antibodies remain positive for life regardless of treatment. MBS item 69316.
Available
HIV serology (4th-generation Ag/Ab)
Mandatory in all syphilis cases — syphilis and HIV co-infection is common (up to 50% co-infection rate in MSM). MBS item 73809.
Available
Hepatitis B surface antigen (HBsAg), Hepatitis C antibody
Screen all patients with newly diagnosed STIs as part of a comprehensive STI screen.
Available
Lumbar puncture (CSF analysis)
Indicated if neurological symptoms present (headache, cranial nerve palsies, hearing loss) or if treatment failure suspected. CSF VDRL is specific but poorly sensitive. CSF protein and cell count are supportive.
Available
Dark-ground microscopy
Of mucous patches or condylomata lata (wet prep). Spirochaetes visible. Sensitivity depends on operator skill. Not widely available outside sexual health clinics.
Treatment — Secondary Syphilis
Jarisch–Herxheimer reaction (JHR): Occurs in ~30–60% of secondary syphilis cases within 2–24 hours of treatment. Presents with fever, rigors, headache, myalgia, and exacerbation of the rash. Self-limiting (resolves within 24–48 h). Pre-warn patients. May require paracetamol and supportive care. In pregnancy, JHR can precipitate preterm labour — manage in consultation with obstetric team.
Benzathine benzylpenicillin
Bicillin L-A® · Long-acting penicillin
Adult dose
1.8 g (2.4 million units) IM stat — single dose for primary/early latent. For secondary/late latent: 1.8 g IM weekly × 3 doses (total 3 injections)
Paediatric dose
50,000 units/kg IM (maximum 2.4 million units). Consult infectious disease specialist for dosing in secondary syphilis.
Renal adjustment
No adjustment required
Route
IM only — deep gluteal or vastus lateralis. Do NOT administer IV (risk of cardiopulmonary embolism — Hoigné syndrome).
PBS status
✔ PBS General Benefit
Doxycycline (Penicillin allergy alternative)
Doryx® · Doxy® · Tetracycline antibiotic
Adult dose
100 mg PO twice daily for 14 days (secondary syphilis)
Paediatric dose
≥8 years: 2 mg/kg PO twice daily (max 100 mg) for 14 days. Avoid in children <8 years (dental staining) unless no alternative.
Renal adjustment
No adjustment required
Contraindications
Pregnancy, breast-feeding, children <8 years (relative). Avoid with isotretinoin (pseudotumour cerebri risk).
PBS status
✔ PBS General Benefit
Follow-Up & Serological Monitoring
Non-treponemal titres (RPR/VDRL) should be checked at 3, 6, and 12 months post-treatment. A four-fold decline in RPR titre (e.g., 1:32 → 1:8) indicates adequate treatment response. Failure of titres to fall four-fold by 12 months constitutes treatment failure and requires re-treatment (with benzathine penicillin 1.8 g IM weekly × 3) and lumbar puncture to exclude neurosyphilis. Patients must be counselled to avoid sexual contact until lesions have fully resolved and to notify all sexual partners (partner notification is a legal requirement in most Australian states/territories under public health legislation).
Primary HIV Eruption (Acute Retroviral Syndrome)
Acute HIV seroconversion illness (acute retroviral syndrome, ARS) occurs in 40–90% of newly infected individuals, typically 2–4 weeks after exposure. The cutaneous eruption is one of the most consistent features and is often the presenting complaint in primary care. ARS is a critical diagnostic opportunity — identifying HIV infection during this phase allows early antiretroviral therapy (ART) initiation, which improves long-term outcomes and reduces onward transmission.
Clinical Features of ARS
- Rash: Generalised, symmetric, erythematous, non-pruritic maculopapular eruption. Involves the face, trunk, and limbs (including palms and soles in ~50%). Can resemble a viral exanthem or drug eruption. Lasts 5–10 days.
- Fever: The most common symptom (~90%). Typically 38.5–40°C.
- Pharyngitis: Non-exudative pharyngitis (distinguishable from GAS pharyngitis).
- Lymphadenopathy: Generalised, non-tender, particularly posterior cervical, axillary, and epitrochlear.
- Mucocutaneous ulcers: Painless oral, oesophageal, or genital ulcers (differentiated from syphilis chancres which are painless but non-ulcerative in many cases).
- Other features: Myalgia/arthralgia, headache, weight loss, diarrhoea, hepatosplenomegaly.
Diagnostic window: Standard 4th-generation HIV Ag/Ab tests detect p24 antigen and anti-HIV antibodies. The window period is approximately 2–4 weeks (may be up to 6 weeks). If clinical suspicion for ARS is high but 4th-generation test is negative, request HIV-1 RNA PCR (viral load) which becomes positive ~10 days post-infection. Repeat serology at 6 weeks if initial test negative.
Investigations
Essential
HIV Ag/Ab combination assay (4th generation)
First-line screening test. Detects p24 antigen (appears ~15 days post-exposure) and anti-HIV-1/2 antibodies (appears ~21–28 days). MBS item 73809. Available at all major pathology providers. Point-of-care tests (e.g., Atomo HIV Self Test) are available OTC in Australian pharmacies but should be confirmed with laboratory testing if reactive.
Available
HIV-1 RNA PCR (viral load)
For suspected ARS when 4th-generation Ag/Ab is negative or indeterminate. Also used to monitor treatment response. MBS item 73812 (restricted to HIV-positive patients or high clinical suspicion).
Available
CD4 count and HIV genotype/resistance testing
At confirmed diagnosis — performed at reference laboratories (e.g., Victorian Infectious Diseases Reference Laboratory, Westmead Hospital). Genotype informs ART selection.
Available
STI screen (syphilis, gonorrhoea, chlamydia, hepatitis B/C)
Comprehensive STI screen mandatory at HIV diagnosis. Syphilis co-infection rates are high in newly diagnosed HIV patients in Australia.
Management
- Immediate referral: Referral to a specialist HIV service (s100 prescriber) for confirmation, baseline investigations, and ART initiation. Current Australian guidelines recommend initiating ART as soon as possible after diagnosis, including during ARS.
- Symptomatic management of eruption: Emollients, topical corticosteroids for pruritus, paracetamol for fever/myalgia.
- PrEP cascade: Assess recent sexual contacts for post-exposure prophylaxis (PEP) if within 72 hours of exposure, or pre-exposure prophylaxis (PrEP) for ongoing risk.
- Public health notification: HIV is a notifiable disease in all Australian states and territories. Notification to the state/territory public health unit is mandatory.
- Patient support: Referral to community organisations (e.g., ACON, Thorne Harbour Health, NAPWHA) for peer support, counselling, and care coordination.
Monitoring
| Condition | Follow-Up Schedule | Key Monitoring Parameters | Treatment Failure Criteria |
|---|---|---|---|
| Acute urticaria | 2–4 weeks; then PRN | Symptom control, medication side effects | Persistence >6 weeks → reclassify as chronic; refer to immunology |
| Drug eruption (morbilliform) | 1 week after drug cessation | Rash resolution, LFTs if hepatitic features | Failure to resolve by 2 weeks — consider alternative diagnosis |
| DRESS syndrome | Weekly for 4 weeks, then 2-weekly for 2 months, then monthly for 6 months | FBC, LFTs, UEC every visit. Thyroid function (TSH, fT4) at 2 and 6 months post-recovery. | Organ function deterioration → escalate to immunology/dermatology |
| SJS / TEN | Continuous inpatient (burns/ICU). Follow-up at 2, 6, and 12 weeks post-discharge. | BSA, SCORTEN, infection markers, ophthalmology review, mucosal assessment | Persistent epidermal sloughing, secondary sepsis, ocular scarring |
| Pityriasis rosea | 2–4 weeks (optional); PRN if not resolving | Rash resolution, pruritus control | Persistence >12 weeks — reconsider diagnosis (biopsy, syphilis serology) |
| Guttate psoriasis | 4–6 weeks post-treatment; 3-monthly for 12 months | Rash clearance, ASOT decline, plaque psoriasis development | Persistent/worsening disease → dermatology referral for systemic therapy |
| Secondary syphilis | 3, 6, and 12 months post-treatment | Quantitative RPR titre — expect 4-fold decline by 6 months | <4-fold decline by 12 months or rising titre — re-treat + LP for neurosyphilis |
| Acute HIV (ARS) | 2–4 weeks post-ART initiation, then 3-monthly until viral suppression, then 6-monthly | HIV viral load, CD4 count, LFTs, renal function, lipid profile, adherence assessment | Detectable viral load at 24 weeks — assess adherence, resistance testing |
Special Populations
Pregnancy
Syphilis: Benzathine penicillin is the only effective treatment for preventing congenital syphilis. Treat with benzathine penicillin 1.8 g IM weekly × 3 (as for non-pregnant). If penicillin allergic, attempt desensitisation in a supervised setting — doxycycline and azithromycin are contraindicated in pregnancy.
Jarisch–Herxheimer reaction in pregnancy: Can precipitate preterm contractions/labor. Admit for observation after first dose in secondary syphilis. Fetal monitoring recommended.
Urticaria: Loratadine and cetirizine are Category B1 (limited human data, no evidence of harm). Avoid first-generation antihistamines (chlorphenamine — sedation, foetal effects). Prednisolone if needed (short courses).
Drug eruptions: Avoid tetracyclines. Topical corticosteroids safe (use lowest effective potency). SJS/TEN management same principles — transfer to ICU/burns.
HIV: Immediate referral to HIV-obstetric service. ART initiation regardless of CD4 count. Mode of delivery depends on viral load at 36 weeks. Breastfeeding: discuss with specialist (Australian guidelines now support breastfeeding with undetectable viral load on ART, with close monitoring).
All pregnant women should have syphilis serology at first antenatal visit (28 weeks in high-risk areas) and at delivery as per Australian antenatal guidelines.
Paediatrics
Urticaria: Very common in children. Often post-viral. Second-generation antihistamines at age-appropriate doses. Avoid hydroxyzine in children <6 months.
Pityriasis rosea: Papular variant more common in children (especially those with darker skin). Atypical locations (face, extremities). Post-inflammatory hyperpigmentation more prominent — reassure families.
Guttate psoriasis: One of the most common forms of psoriasis in children. Tonsillectomy may be considered in recurrent guttate psoriasis associated with chronic streptococcal carriage — discuss with ENT.
Drug eruptions: Amoxicillin-associated morbilliform eruption is the most common drug eruption in children (especially with concurrent EBV infection — ampicillin/amoxicillin rash in infectious mononucleosis). Not a true penicillin allergy in most cases.
Syphilis: Congenital syphilis — assess all infants born to seropositive mothers. Clinical features: hepatosplenomegaly, rash, pseudoparalysis of Parrot, snuffles, rhagades. Treatment: aqueous crystalline penicillin G 50,000 units/kg IV q12h (first 7 days of life) then q8h for 10 days (total 10 days).
Children <8 years: avoid doxycycline unless no alternative (for syphilis, consult ID specialist for alternative regimens).
Elderly
Drug eruptions: Higher risk due to polypharmacy. Drug eruption should be the leading differential for any new widespread rash in elderly patients taking multiple medications. The SCORTEN criteria for SJS/TEN include age >40 as a risk factor.
Sedating antihistamines: Avoid first-generation antihistamines (promethazine, chlorphenamine) — anticholinergic burden, falls risk, confusion. Use cetirizine or loratadine at standard doses; fexofenadine is least sedating.
Corticosteroids: Use with caution — increased risk of osteoporosis, hyperglycaemia, delirium, and immunosuppression. Short courses only. Consider bone protection if prolonged use anticipated.
Allopurinol SJS/TEN: HLA-B*5801 testing strongly recommended before initiating allopurinol in populations with Southeast Asian, Korean, Han Chinese, or European ancestry (increasingly adopted in Australian rheumatology practice).
Review all medications (including OTC and complementary medicines) in any elderly patient presenting with an acute eruption.
Renal Impairment
Antihistamines: Cetirizine and loratadine — dose reduction required in severe renal impairment (eGFR <30). Fexofenadine preferred (minimal renal adjustment needed at lower doses).
Doxycycline: No renal adjustment required — preferred tetracycline in CKD. Avoid minocycline and tetracycline in renal impairment.
Benzathine penicillin: No adjustment required.
DRESS: Nephritis may occur; monitor UEC closely. Adjust corticosteroid doses if significant renal impairment (affects prednisolone metabolism to prednisone).
Patients on dialysis with suspected SJS/TEN require transfer to a centre with both burns/ICU and renal replacement therapy capability.
Hepatic Impairment
DRESS syndrome: Hepatitis is the most common organ involvement. Monitor LFTs closely. Avoid hepatotoxic medications. Corticosteroids are the mainstay of treatment for DRESS-related hepatitis.
Antihistamines: First-generation antihistamines (promethazine, chlorphenamine) may precipitate hepatic encephalopathy — avoid in liver disease. Second-generation agents are preferred.
Prednisolone: Preferred over prednisone in severe hepatic impairment (prednisolone does not require hepatic conversion, unlike prednisone).
Syphilis: Penicillins are safe in hepatic impairment. Monitor LFTs if concurrent hepatitis B or C co-infection.
Liver function should be assessed in all patients with drug eruptions — drug-induced liver injury (DILI) may coexist with cutaneous drug reactions.
Immunocompromised
HIV/AIDS: Syphilis may present atypically in HIV-positive patients (aggressive ulceration, rapid progression). All HIV-positive patients with syphilis should have neurological assessment. CD4 count may influence treatment decisions.
Drug eruptions: Higher incidence and severity in immunocompromised patients. DRESS with HHV-6 reactivation is more common. Immunosuppressed patients on TMP-SMX (e.g., for PJP prophylaxis) are at particular risk for morbilliform eruptions and SJS/TEN.
Biologic therapies: Patients on TNF-α inhibitors, IL-17 inhibitors, or JAK inhibitors may present with paradoxical psoriasiform eruptions or drug-induced psoriasis-like reactions — referral to dermatology is essential.
Transplant recipients: All skin eruptions require urgent evaluation — drug eruptions (tacrolimus, mycophenolate), viral exanthems (CMV, EBV), and infections (fungal, herpes) must be distinguished.
Consider HIV testing in any patient presenting with unexplained secondary syphilis — co-infection rates are high, and undiagnosed HIV is a significant concern in Australia.
Aboriginal and Torres Strait Islander Health Considerations
Aboriginal and Torres Strait Islander Health
Aboriginal and Torres Strait Islander Australians experience a significantly higher burden of sexually transmitted infections, including syphilis, compared to non-Indigenous Australians. The ongoing syphilis outbreak, which began in 2011 in northern Australia, has disproportionately affected Indigenous communities. Additionally, skin conditions such as scabies, impetigo, and post-streptococcal glomerulonephritis are more prevalent, reflecting broader social determinants of health including overcrowded housing, limited access to healthcare, and the effects of systemic disadvantage.
Key Considerations
Point-of-care testing (POCT): Rapid treponemal POCT (e.g., DPP Syphilis Screen & Confirm assay) is available in many remote Aboriginal health services across northern Australia, enabling same-day diagnosis and treatment initiation for syphilis. This is a key strategy under the national syphilis action plan. Contact your state/territory sexual health program for POCT availability and training.
Resources: RHDAustralia (www.rhdaustralia.edu.au) provides clinical guidelines for STI management in remote Aboriginal and Torres Strait Islander communities. The Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine (ASHM) offers training modules on syphilis management and POCT.
Quick Reference — First-Line Treatment Summary
Acute urticaria
Cetirizine 10 mg PO daily (or loratadine 10 mg, fexofenadine 180 mg)
PRN; up-dose to 4× if needed
Add short-course prednisolone for severe flares
Morbilliform drug eruption
Cease causative drug + topical corticosteroid + cetirizine
7–14 days
Self-limiting after drug cessation (7–14 days)
DRESS syndrome
Prednisolone 1 mg/kg/day PO, slow taper 6–8 weeks
6–8 weeks minimum
Monitor thyroid function for 6 months post-recovery
SJS / TEN
Cease all suspect drugs → Burns/ICU → Supportive care
Inpatient until re-epithelialisation
SCORTEN for prognosis; no proven disease-modifying therapy
Fixed drug eruption
Cease drug + mometasone 0.1% OD to site
7–14 days
Document causative drug; flag in My Health Record
Pityriasis rosea
Emollients ± topical corticosteroid ± cetirizine
Self-resolves 6–8 weeks
Exclude syphilis serology first; NB UVB if persistent
Guttate psoriasis
Phenoxymethylpenicillin 500 mg PO BD + betamethasone 0.05% OD
Antibiotic 10 days; topical 2–4 weeks
Treat streptococcal trigger; NB UVB if widespread
Secondary syphilis
Benzathine penicillin 1.8 g IM weekly × 3
3 weekly injections
RPR at 3, 6, 12 months; all partners; HIV test
Acute HIV seroconversion
Referral to HIV specialist for ART initiation
Lifelong ART
Notify public health unit; contact tracing; PEP/PrEP for contacts
📚 References
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