Alopecia refers to hair loss from any part of the body for any reason. There are several types, ranging from thinning hair to complete baldness. Alopecia is broadly classified into 2 categories. In non-scarring alopecia, the hair follicles are still alive and hair can be grown. In scarring alopecia, the hair follicles are destroyed and will not regrow hair.
Diffuse alopecia (thinning scalp hair) is common among seniors, both men and women alike.
Androgenic alopecia, also known as "male pattern baldness" and "female pattern baldness," can strike younger as well as older people. It's genetic, so having a family history can predict if you might inherit it. In both men and women, it's linked to having an excess of male hormones (androgens) around the hair follicles, which can block hair growth. Women are more likely to develop androgenic alopecia after menopause, when they have fewer female hormones.
Most cases of hair loss are due to androgenic alopecia. Approximately 50% of men by the age of 50 years and 15% of women before the time they reach menopause have some degree of androgenic alopecia.
Alopecia areata typically causes a few temporary bald patches on the scalp. It tends to run in families and often strikes in childhood. The hair loss seems to be part of an immune system problem, in which the body's natural defences mistakenly attack its own tissue. Once the hair has fallen out in certain spots, new growth is suppressed for weeks or months. This type of alopecia sometimes affects people who have other "autoimmune" diseases like thyroid disease, lupus, or pernicious anemia. Sometimes, it may produce complete scalp baldness (alopecia totalis) or total loss of body hair (alopecia universalis).
Telogen effluvium is a form of hair loss often associated with pregnancy, medication use, life stress, diets, or surgery. It results in a larger amount of hair cycling into the resting (telogen) state where the hairs are ready to fall out. This type of alopecia usually improves on its own after several months. While it usually resolves, it can become chronic without regrowth of hair.
Scarring alopecia is a form of hair loss that results in scarring, where scarred areas will not regrow hair. This type of alopecia may have several causes. For example, fungus can leave permanent bald patches.