Synopsis
Recognise a common uncomplicated exanthematous drug eruption, identify features that indicate severe cutaneous adverse reaction, and document medicine causality without over-labelling.
- Typical lesions are symmetrical pink, red, violaceous or brown macules and small papules beginning on trunk, often with itch and no mucosal erosion.
- An uncomplicated eruption usually appears days after starting a medicine, but latency shortens after previous sensitisation and varies with the culprit.
- Create a complete timeline including prescriptions, over-the-counter products, contrast, vaccines and intermittent medicines started or stopped in the preceding weeks.
- Examine face, mouth, eyes, genital mucosa, skin tenderness, blistering, pustules, purpura, nodes and physiology before calling the eruption benign.
- Stop the suspected medicine when clinically safe after discussing essential treatment alternatives; do not abruptly withdraw a vital medicine without a replacement plan.
- Record drug, formulation, indication, dates, latency, morphology, severity and certainty rather than entering rash alone.
- Morbilliform 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 Morbilliform drug eruption, document the working diagnosis, excluded emergencies, uncertain culprit or trigger, treatment response and the exact safety-net given.
Key red flags
Skin pain, dusky or targetoid lesions, blisters, detachment, mucosal ulceration, facial oedema, fever, lymphadenopathy, pustules, eosinophilia or liver and kidney abnormalities require urgent escalation.
Facial oedema, high fever, skin pain, mucosal injury, blistering, detachment, pustules or purpura mandates urgent reassessment.
Lymphadenopathy, jaundice, breathlessness, reduced urine output or abnormal liver and renal tests suggests systemic drug hypersensitivity.
Investigation priorities
Identify plausible culprit exposures and competing infection.
Management branches
The eruption is symmetrical and itchy, mucosa is normal, skin is not painful and no organ or physiological abnormality exists.
- Review the medicine timeline, stop the most plausible non-essential culprit after arranging any necessary treatment substitute and record uncertainty.
- Use emollient, a site-appropriate topical corticosteroid and a non-sedating antihistamine when itch is prominent, avoiding unnecessary systemic steroids.
- Review within a defined interval and instruct the patient to seek urgent help for fever, facial swelling, mucosal pain, blisters or systemic symptoms.