what causes erthema
It is usually caused by a reaction to medications, infections (especially herpes simplex virus), or illness. Erythema nodosum is a form of erythema that is accompanied by tender lumps, usually on the legs below the knees, and may be caused by certain medications or diseases.hotosensitivity is caused by a reaction to sunlight and tends to occur when something, such as an infection or a medication, increases your sensitivity to ultraviolet radiation. Erythema multiforme is characterized by raised spots or other lesions on the skin.