Hair loss, or alopecia, is the loss of hair on the body. The various types of alopecia include androgenic alopecia, alopecia areata, telogen effluvium, and anagen effluvium.

Male-pattern hair loss usually starts at the front hairline or crown, whereas female-pattern hair loss occurs as diffuse thinning on the top of the head. Other types include alopecia areata (patchy loss) and telogen or anagen effluvium (overall thinning).

Hair loss is diagnosed through various methods, including visual examination, medical history, biopsy, laboratory testing, and the hair pull test.

The only FDA-approved drugs for androgenic alopecia are minoxidil and finasteride. Other treatments include dutasteride, prostaglandin analogs, platelet-rich plasma injections, antiandrogens for women, and corticosteroid injections for alopecia areata.

Supplements that have been studied for hair loss include oral vitamin E, saw palmetto, or a mixture of compounds (such as amino acids plus vitamins), and topical pumpkin seed oil, melatonin, or procyanidin.

Limited research suggests that the intake of raw vegetables or fresh herbs may be associated with a lower risk of androgenic alopecia and that certain nutrient deficiencies may increase hair loss risk in some individuals.

Other treatments for hair loss (specifically for androgenic alopecia) include red light therapy, microneedling to enhance minoxidil's effects, and ketoconazole-containing medicated shampoos.

Hair loss can result from medical conditions, medications, infections, or autoimmune issues like alopecia areata. Male-pattern baldness is mainly driven by dihydrotestosterone, whereas genetics and aging affect both male-pattern and female-pattern baldness.