Synopsis
Recognise true target lesions and mucosal severity across skin tones, identify infection-related triggers, separate erythema multiforme from Stevens–Johnson syndrome, and treat acute and recurrent disease safely.
- A classic erythema-multiforme target is a fixed round lesion with three concentric zones: a dusky or blistered centre, a paler oedematous ring and a sharply defined outer erythematous rim.
- Lesions arise symmetrically on backs of hands, feet and extensor limbs and spread centripetally; they remain in the same place for days, unlike individual urticarial wheals.
- On brown or black skin, the outer ring may be purple-brown and central duskiness grey or deep brown; palpability, oedema, blistering and the concentric outline may be clearer than red colour.
- Herpes simplex virus is the common recurrent trigger and the target eruption often begins about ten days after a cold sore, although the herpes lesion may already have resolved.
- Erythema multiforme major includes significant mucosal disease but remains clinically distinct from Stevens–Johnson syndrome and toxic epidermal necrolysis.
- Prominent respiratory-associated mucositis with few skin lesions suggests reactive infectious mucocutaneous eruption rather than forcing every case into erythema multiforme.
- Diagnosis is usually clinical; biopsy is useful for atypical, persistent or high-stakes presentations but histology must be interpreted with distribution, medicines, mucosa and skin pain.
- First-line limited disease care is trigger review, emollient and symptom relief; severe mouth disease needs analgesia, hydration and assessment of nutrition, eyes and other mucosae.
- Frequent HSV-associated recurrences merit continuous antiviral suppression, commonly aciclovir 400 mg twice daily for at least six months with specialist review.
Key red flags
Skin pain, systemic toxicity, rapidly expanding central duskiness, epidermal detachment, inability to drink, reduced urine, breathing difficulty, visual symptoms, genital erosions, pregnancy, immunosuppression or diagnostic uncertainty requires same-day specialist assessment.
Painful oral erosions and haemorrhagic lip crust can accompany classic skin targets; ocular, genital or airway symptoms increase severity and referral need.
Fever, skin pain, flat atypical truncal targets, purpura, extensive mucositis and detachment after medication indicate a different emergency phenotype.
Investigation priorities
Confirm target morphology, map severity and identify an SJS or TEN pattern.
Management branches
A sudden symmetrical annular or targetoid eruption is reported.
- Establish whether individual lesions are fixed for days and have three palpable zones, then map acral versus truncal distribution and photograph representative sites with consent.
- Examine all mucosae, measure skin pain and detachment and record systemic observations before asking about HSV, respiratory infection and a complete medicine timeline.
- Manage as possible SJS or TEN and seek same-day dermatology advice if targets are flat or atypical, pain or toxicity is prominent, multiple mucosae are severe or the diagnosis remains uncertain.
Classic targets are limited, the patient is systemically well and oral intake is secure.
- Explain the usual self-limited two-to-four-week course, use cool emollients and a short site-appropriate topical corticosteroid course for inflamed itchy plaques.
- Use a non-sedating oral antihistamine when itch is troublesome and simple analgesia when safe, while avoiding unneeded new medicines during diagnostic evolution.