Although we tend to think of it as a guy thing, million of women have unexpected hair loss. But some experts believe that dramatically thinning hair--the fallout (literally) from stress, poor nutrition, an underlying medical condition, harsh hair treatments, or heredity, among other causes--is as common in women as it is in men.

Roughly half of all women over age 40 experience excessive hair loss. And one study estimates that it occurs in 75 percent of women over age 65. If you fear that your hair may be thinning significantly, keep reading to learn more about hair loss in women--what causes it, what it looks like, and what to do about it.

What's Causing My Hair Loss?
The most common type of hair loss from the scalp (as opposed to hair loss all over the body) is androgenetic alopecia (AA), or pattern baldness.

Who Gets It?
AA is hereditary. A history of the condition in men or women on either side of your family increases your risk of developing it and also influences the age at which your hair loss begins, the speed with which it occurs, and its pattern and extent.
What Does It Look Like? Most often a woman's hair simply thins gradually and diffusely on the top of or all over her head. In both men and women, AA is permanent and continues with aging.

What Can I Do?
Be sure to consult an expert who can help determine why your hair is thinning so you can treat the problem correctly. To find a physician in your area who specializes in diseases of the skin and hair, check out our dermatologist listing in your metro area. In the meantime, don't be afraid to wash your hair. However, you want to make sure to avoid brushing or teasing your hair. A new hairdo can also help hide traces of baldness, while giving you a beautiful new look.

Am I Losing It?
The truth is, you are--everyone is. Most of us shed 50 to 150 hairs a day. Once a hair is shed, a new hair from the same follicle replaces the lost strand--unless you have AA. AA occurs when the rate of hair shedding exceeds the rate of hair regrowth, or when the new hair shafts that grow in are thinner than the previous ones, making your mane look progressively less thick.

Hair Today, Gone Tomorrow
You can experience temporary hair loss, and unlike androgenetic alopecia, it's not gradual. Two for-women-only causes of temporary hair loss are giving birth and starting birth control pills.