Synopsis
Recognise site-specific recurrence after medicine exposure, distinguish local fixed eruption from generalised bullous disease, and document the culprit and residual pigmentation accurately.
- A fixed drug eruption recurs at the same sharply demarcated skin or mucosal site after re-exposure and usually leaves residual hyperpigmentation.
- Active lesions may be red, violaceous, dusky brown or blistered; ask the patient whether a dark mark was present before the current flare.
- Search intermittent medicines, analgesics, antibiotics, supplements and combination cold remedies used in the hours or days before every episode.
- One episode may involve one plaque, but additional sites often appear with later exposures and generalised bullous disease can be life-threatening.
- Do not perform casual oral re-challenge when the original reaction was bullous, generalised or involved mucosa.
- Record the specific suspected drug, recurrence pattern, sites, severity and uncertainty, with photographs obtained after consent.
- Fixed drug eruption must be assessed by lesion duration, onset, distribution, symptoms, mucosal findings, systemic physiology and the full medicine timeline rather than by colour alone.
- For Fixed drug eruption, document the working diagnosis, excluded emergencies, uncertain culprit or trigger, treatment response and the exact safety-net given.
Key red flags
Numerous lesions, generalised blistering, mucosal erosions, skin pain, fever, dehydration or diagnostic uncertainty with SJS or TEN requires same-day hospital assessment.
Multiple tender dusky plaques with extensive blisters, detachment or mucosal injury require urgent SJS or TEN-level assessment.
Investigation priorities
Demonstrate repeated exposure before recurrence at a fixed site.
Management branches
One or few fixed plaques occur without fever, mucosal loss, widespread blistering or systemic illness.
- Construct a precise recurrent-exposure history, stop the likely non-essential culprit and identify all combination products containing it.
- Use cool care, emollient and a site-appropriate topical corticosteroid for short-term symptoms while monitoring for new lesions.
- Photograph with consent, explain residual pigment and arrange review if the eruption spreads, blisters or affects mucosa.
Key medicines
Betamethasone valerate 0.1% creamApply thinly to a localised intact plaque once or twice daily for the shortest effective course, not exceeding four weeks under the licensed product directions.Avoid application to eroded mucosa, infected skin, face or large areas unless directed; review atrophy and systemic absorption, especially under occlusion.
Cetirizine 10 mg tabletsAdults and adolescents aged 12 years and over take 10 mg orally once daily, with renal adjustment as specified by the product information.Review drowsiness, alcohol, driving, renal function, pregnancy and breastfeeding; do not interpret symptom relief as evidence that bullous progression is safe.