Alopecia is not a single disease but a group of conditions with distinct underlying causes. Androgenetic alopecia, the most prevalent form affecting up to 50% of men and 40% of women by age 50, results from a genetic sensitivity to dihydrotestosterone (DHT). This hormone miniaturizes hair follicles over time, progressively shortening the growth cycle until follicles produce only fine vellus hairs or cease production entirely.
Alopecia areata, affecting approximately 2% of the population, is an autoimmune disorder in which T-lymphocytes mistakenly target the hair follicle bulb. The immune attack disrupts the growth phase (anagen), causing sudden, well-defined patches of hair loss. In more severe cases, this can progress to alopecia totalis (complete scalp hair loss) or alopecia universalis (total body hair loss). Traction alopecia develops from prolonged mechanical stress on follicles due to tight hairstyles, extensions, or chemical treatments. Frontal fibrosing alopecia involves lymphocytic inflammation that permanently destroys follicles along the frontal hairline. Early diagnosis by a dermatologist is essential because some forms cause irreversible scarring if untreated.
