What could lead to sudden hair loss in a 39-year-old woman? Disease, dietary changes, stress? "Many things can result in hair loss. Research is ongoing," says Dr. Maria Hordinsky, an associate professor of dermatology at the University of Minnesota, who has written extensively about the subject. "A generation ago doctors thought stress was the big culprit. Now we are focusing on how various factors result in biochemical changes in the body." While Hordinsky will not speculate on what might be ailing any patient she hasn't seen, she did discuss possible causes with correspondent Margaret Nelson.

What accounts for sudden hair loss?

When hair falls out overnight or within a few days, it could be infection, reactions to medicine or the onset of hereditary baldness. But it's usually either telogen effluvium or alopecia areata. Telogen effluvium is a condition in which hair moves quickly through the growth cycle, then falls out. It tends to affect new mothers, people on low-protein diets, people having an adverse reaction to medicine or those suffering from very high fevers.

How does that differ from alopecia areata?

If the hair loss is patchy, the early diagnosis is usually alopecia areata, an autoimmune disease. If the hair loss is extensive, only careful study will determine whether it is telogen effluvium or alopecia areata, which comes in different forms and widely differing severities. Patients with short-term patchy disease may be genetically different from patients with extensive disease of long duration. The most common is a patchy, nonscarring hair loss in which one or more circular patches of hair fall out, sometimes overnight. Often as sudden is alopecia totalis, where all scalp hair is lost. Finally, alopecia universalis results in hair loss over the entire body.

How long does the typical hair-loss episode last?

Alopecia areata can last from days to years and can recur over a lifetime, but most episodes can be successfully treated within several months. Telogen effluvium usually resolves itself without treatment within several months.

By Margaret Nelson and Maria Hordinsky, People Magazine, 09-30-1996