NHS ChoicesMedical Reference
Alopecia is loss of hair and sometimes baldness.
In some cases, hair loss is a side effect of cancer treatment drugs, in which case it is usually only temporary.
However, any type of hair loss can lead to problems with confidence and self-esteem. The main types of hair loss are summarised below.
The commonest form of hair loss is male-pattern baldness, called androgenic alopecia. This can affect both men and women.
Alopecia areata is another type of hair loss, involving patches of baldness that may come and go. It affects about one in 100 people, mostly teenagers and young adults, and it runs in the family in one in five cases.
Alopecia areata is thought to be caused by a problem with the immune system. There is no proven effective treatment, but in most cases the hair grows back after about a year.
One in five people with alopecia areata may go on to develop a more severe form of hair loss - alopecia totalis (no scalp hair) or alopecia universalis (no hair on the scalp and body).
Telogen effluvium is a common type of alopecia where there is widespread thinning of the hair, rather than specific bald patches. Hair is shed from the scalp and from other areas of the body, usually as a reaction to stress or medication. Telogen effluvium tends to go away on its own after several months.