reddening of the skin caused by the dilatation of blood vessels. Erythema sometimes occurs by reflex action and disappears quickly, for example, when one feels ashamed or angry. With inflammation, the condition lasts longer. It appears as a result of exposure to chemicals and physical factors (friction, heat, cold, ultraviolet radiation) and in some infectious diseases (scarlet fever, measles, erythema infectiosum) and skin diseases (dermatitis). It also occurs as a result of poisoning and disturbances in blood circulation.