Alopecia areata is a condition that is typified by patchy hair loss over the scalp or body. It comes in several forms ranging from a single patch to total body hair loss (alopecia universalis). Its cause may be difficult to diagnose but many cases appear to link directly to imbalances in the immune system that can be treated effectively. In most cases hair will reappear on its own but some patients develop more extreme variations that are more difficult to treat.