• History of preceding sore throat or cold

• Low-grade fever

• Drug history: barbiturates, sulphonamides, phenytoin, penicillins

• Blister-like skin rash with intense itching

• Mouth ulcers: mucosal involvement suggests Stevens–Johnson syndrome

• History of recurrent episodes: suggests herpes simplex infection.

• Target-shaped lesions (Fig. 164.1), usually over the palms, soles and skin. A classical target lesion consists of three concentric zones of colour change: typically there is a central, dark, purple area or blister surrounded by a pale, oedematous round zone; this, in turn, is surrounded by a peripheral rim of erythema

• Pleomorphic eruption with macules, papules and bullae.

• Look at the mucous membranes of the mouth (cutaneous and mucosal lips, gingival sulcus, sides of tongue), nares and conjuctiva (Stevens–Johnson syndrome).

• Tell the examiner that you would like to examine the external genitalia for ulcers.