In the Thick of It

Overall Thinning

YOUR HAIR IS: Thinning slightly all over your head. You're also seeing more strands in your shower, in your brush, and on your clothes. And even after styling, your hair isn't as full as it usually is.

THE CONDITION: Telogen effluvium. Healthy hair rotates through three cycles: growing (anagen), transitional (catagen), and resting (telogen). The whole process usually takes about three months, explains Dr. McMichael. When your body endures trauma, however, too many hairs can suddenly shift to the resting phase, and six weeks to six months later you may start losing handfuls of hair.

THE CAUSES: This problem can be triggered by medication, surgery, severe illness, childbirth, perimenopause, or infection. "The shedding usually begins after this kind of event, so people don't always make the connection," says Dr. McMichael. An over- or under-active thyroid can also be a cause.

Similarly, it takes weeks or months for a new prescription to cause noticeable thinning. "We're finding that more and more of our patients are losing hair due to drug side effects," says Neil Sadick, MD, a clinical professor of dermatology at NewYork Presbyterian Hospital/Weill Cornell Medical College who has a private practice in New York City. "By adjusting the medication, you can often stop or reverse the loss completely." The commonest drug culprits are antidepressants, birth control pills, and even ibuprofen (when taken daily for months on end). Other possible -- and treatable -- causes include nutritional deficiencies (most often of iron, zinc, or the B vitamin biotin), thyroid disorders, and the early stages of diabetes.

YOUR DOCTOR MAY: Do a pull test, removing some hairs to assess how many come out easily and whether those hairs are of normal diameter or the same diameter as the other hairs on your head.

THE TREATMENTS: If the cause is a single event like childbirth, telogen effluvium tends to correct itself over a period of months without medical treatment. Otherwise, you need to stop the drug or treat the condition. "Once underlying causes -- such as drugs, diet, or a one-time event -- are eliminated or end naturally, the hairs return to their normal cycles," says Dr. Callender.