Up to 80 percent of men and 50 percent of women experience hair loss — but hair loss is not one condition, it is many. Androgenetic alopecia, telogen effluvium, alopecia areata, and traction alopecia all have completely different causes and treatments. This complete guide covers the hair growth cycle, all four major types with how to identify each, a 6-type quick reference table, the medical conditions and medications that cause hair loss, and the full treatment spectrum from