The name is fancy -- telogen effluvium -- but all it means is increased hair shedding. Lots of hair shedding. For various reasons, many hair follicles enter the exogen stage all at once.
The good news here is that hair lost this way almost always grows back in a few months.
Chemotherapy forces growing follicles into the catagen stage. The hair shaft doesn't develop properly, so the hair breaks and falls out.
The good news is that when chemotherapy is over, the follicles regenerate. Healthy, new hair grows again. The bad news is that, in the short term, chemotherapy causes near total hair loss.
Sometimes a person's immune system attacks the cells of the growing hair bulb. This autoimmune condition is called alopecia areata.
Just as in chemotherapy, hair follicles are forced into the catagen phase. Hairs break and fall out, usually in patches scattered across the scalp.
Sometimes the immune system attacks only the hair bulb. In this case, the hair follicles regenerate when the immune system is brought under control.
Alopcia areata is not related to a more serious condition known as cicatricial alopecia, in which the immune system attacks the stem cells in the bulge of the folicle. This results in permanent hair loss.
Today's Hair-Loss Treatments: Drugs
It's still not entirely clear how minoxidil works. And there's disagreement about how well it works. Used properly -- twice a day, massaged deep into the scalp -- it slows new hair loss. It also promotes new hair growth, although experts disagree about how much.
"Two-thirds of men do get acceptable hair growth -- moderate to very good hair growth," Andrew Kaufman, MD, tells WebMD. Kaufman, a hair-transplant surgeon, is assistant professor of clinical dermatology at UCLA, and medical director of the Center for Dermatology Care, Thousand Oaks, Calif.