Erythema, redness due to sunburn, is a visible sign of skin damage caused by overexposure to the sun's ultraviolet rays The amount of sunlight needed to cause minimally perceptible sunburn is known as the minimal erythema dose (MED)
Abnormal skin redness from increased blood flow, caused by dilation and irritation of surface capillaries. It has a variety of manifestations. In erythema multiforme, a symptom complex seen in several diseases, spots appear suddenly, often with a bull's-eye pattern. It may become life-threatening in severe cases; in mild cases symptoms may recur. Hormone treatment may be effective. In erythema nodosum, a hypersensitivity reaction usually associated with strep infection (see streptococcus), drugs, or the disease sarcoidosis, painful red nodules appear in the deeper skin layer of the lower legs. They usually disappear over several weeks and do not recur. Another form of erythema is pellagra
redness around the site of the injection when a Mantoux skin test is done; erythema is not considered when the reaction size is measured, because redness does not indicate that a person has TB infection
Redness of skin along vein track that results from vascular irritation or capillary congestion in response to irritation; may be a precursor to phlebitis