Erythema is an abnormal redness of the skin caused by capillary congestion. It is one of the cardinal signs of inflammation.

It can be caused by infection, massage, electrical treatments, or exercise, any of which can cause the capillaries to dilate, resulting in redness.

Massage causes the blood vessels to be compressed, forcing blood forward. As pressure is released, the vessels return to their normal size and blood rushes in to fill the space created. Fresh, oxgenated blood is brought to the area and so will nourish the tissue and help with tissue repair.