Q: Why does a hair transplant work? – L.L., Salem, Massachusetts

A: Hair transplantation works because hair taken from the permanent zone in the back and sides of the scalp maintains its original characteristics when transplanted to a new place in the balding area in the top of the head. This property of hair is called “donor dominance” and is the reason why hair transplants are possible.

The hair follicles in areas that go bald are genetically susceptible to DHT, a breakdown product of testosterone. In response to DHT, these hair follicles miniaturize (decrease in size) until they eventually disappear. When follicles from the permanent zone, that are resistant to the effects of DHT, are moved to a balding area, they maintain this property and continue to grow.