Alopecia areata: This disease causes hair loss and often occurs in otherwise healthy people. Alopecia (al-oh-PEE-shah) means hair loss. When a person has a medical condition called alopecia areata (ar-ee-AH-tah), the hair falls out in round patches. The hair can fall out on the scalp and elsewhere on the body. Alopecia areata can cause different types of hair loss. Each of these types has a different name: Alopecia areata (hair loss in patches). Alopecia totalis (lose all hair on the scalp). Alopecia universalis (lose all hair on the body). Not everyone loses all of the hair on the scalp or