Forty percent of the people seeking treatment for hair loss are women, according to the American Hair Loss Association (AHLA). While factors like stress, hormonal changes, and illness can be at fault, genetics are usually to blame for most people who lose their hair early, says Richard Mizuguchi, M.D. director of hair restoration surgery at St. Luke’s-Roosevelt Hospital Center in New York City. The same hormonal mechanism that makes men’s hair recede is also at play when women lose hair, although women are more likely to have thinning all over their scalps than in one specific spot. The culprit is an excess of male androgenic hormones, which essentially tell the hair follicles that their services are no longer needed. Rogaine can help reverse this kind of loss, says Dr. Mizuguchi.