Alopecia

Alopecia is a condition in which hair on the head becomes thinner or falls out entirely in specific areas. It most commonly begins at the front hairline and the top of the head, and progresses gradually. The general medical term for hair loss is alopecia.

Hair grows from follicles embedded in the scalp. Follicles undergo cycles: a growth phase, a resting phase, and a shedding phase in which hair falls out. Hair normally sheds in small quantities daily, but is replaced. Alopecia occurs when follicles shrink (miniaturization) or stop producing new hair.

Types

The most common form is androgenetic alopecia, linked to genetics and androgen hormones. In men it appears as a receding hairline and thinning at the crown; in women it typically manifests as overall thinning of the hair. Another type, alopecia areata, results from the immune system attacking hair follicles, causing patches of baldness. Telogen effluvium is temporary hair loss from specific causes such as illness, stress, childbirth, or malnutrition.

Causes and contributing factors

Family history and androgen hormones are the basis of the most common form. Other conditions are also associated: iron or nutritional deficiency, thyroid disease, cancer treatment (chemotherapy), certain medications, and scalp infections such as fungal infections. Chronic hair pulling or harsh treatment with tight styles or harsh chemicals can cause traction alopecia.

Diagnosis and treatment

A dermatologist bases diagnosis on the patient's history, examination of the pattern of loss, and sometimes blood tests or scalp biopsy. Treatment depends on the cause. Topical and oral medications can slow male-pattern hair loss, and hair transplantation moves follicles from the back of the scalp to thinning areas. When the cause is nutritional deficiency or a reversible condition, hair often regrows once the underlying cause is addressed.