30. Red skin

A 56-year-old woman presented for evaluation of a skin rash of 5 hours duration. This rash consisted of discrete red maculo-papules (Figure 1) which started initially from her face and neck and spread within 2 hours onto her abdomen and arms and legs. This skin rash was pruritic and associated with nausea, anxiety and some breathing difficulties. The patient suffered only from psoriasis and mild diabetes controlled by diet, and shingles two months previously. Penicillin was the only drug taken by the patient, over the previous 4 days, for treatment of a periapical infection. No history of food, plants, cosmetic or animal allergies was recorded.

This skin rash was an allergic drug reaction to penicillin. This is a very common side-effect and appears within 5–6 days of drug uptake and ranges from mild to life-threatening. This is a body reaction to histamine release and can be either a mild reaction, including an acute itching rash, abdominal upset and nausea, as seen in this patient, or a severe form causes breathing problems, facial or tongue oedema and confusion and collapse (anaphylaxis). The direct contact of the skin with various allergens or irritants from plants or foods can cause a similar red rash known as contact dermatitis. However, this dermatitis differs in that it is characteristically restricted only to the areas of allergen exposure, and its maculo-papular lesions contain clear fluid (vesicles or small bullae). A vesicular exanthema is also often seen in patients with chickenpox or with insect bites but their clinical picture and symptomatology is different.