Erythema Multiforme

Erythema multiforme (EM) is an acute, immune-mediated hypersensitivity reaction. Herpes simplex virus (HSV) is the most common precipitant. The virus does not need to be present in every skin lesion: after the trigger, cytotoxic T cells injure keratinocytes, producing the visible eruption. That immune injury creates the lesion that gives EM its name. A typical target has a dusky or darker centre, a pale edematous ring, and an outer erythematous halo. Lesions usually appear suddenly, are distributed symmetrically on the hands, feet, arms, or legs, and remain fixed in place for several days. They may be itchy, burning, or painful. Mucosal involvement can occur. Painful oral lesions may interfere with eating and drinking; ocular or genital lesions can threaten function and require a lower threshold for urgent assessment. EM is often described as EM minor when mucosal disease is absent or limited and EM major when mucosal involvement is prominent. The practical nursing question is not simply which label applies, but whether the patient can hydrate, see normally, void, and remain systemically well. An experienced nurse notices two features early:...