I am 30, and I've been losing my hair like crazy recently. It comes out when I wash it, when I comb it, even when my husband runs his fingers through it! What's going on?

-- Valeria

Hair goes through a constant cycle of growing and shedding. Sometimes much of the head will be in the same cycle, so a large amount of hair comes out at once; new hair is growing in at the same time, but because hair falls out faster than it comes in, thin hair will be the result. Usually within 6-12 months, the hairs will once again be out of cycle, so you will only lose about 100 hairs a day instead of thousands at a time. Stress, whether physical or emotional, can cause the hairs to cycle all at once.

Another possible cause for hair loss is increased male hormone levels or unusual sensitivity of your hair follicles to normal amounts of male hormones. (All women produce some amount of the male hormone testosterone.) This is associated with a short growth phase, so hairs fall out more rapidly than they come in. This problem may be partially hormonal, in which case it may be evaluated by blood tests. Or it may be partially genetic; look at your family.

Some medical conditions like thyroid disease can also cause hair loss and can be evaluated by your doctor.