How to straighten hair with a flat iron

Everyone loses between 40 and 120 strands a day, depending on how much hair you have, your age and your hair's growth cycle. People with fine hair tend to have more of it and therefore will lose more of it than their thicker-haired sisters and brothers. Your hair also thins as you get older, particularly after menopause for women. But unlike aging men, the thinning tends to stop after awhile.

Here are common causes of thinning and hair loss:

1. Seasonality. You'll lose the most hair in the fall -- typically November and December when hair reaches maturity in its growth cycle.

2. Diet. Hair loss can occur through poor dieting. According to dermatologist George Cotsarelis, M.D., director of the University of Pennsylvania Hair and Scalp Clinic, iron deficiency may be the cause. He states in the April 2006 issue of "Ladies Home Journal," it might be worth checking your levels with your doctor and take a supplement if they're low.

3. Aging. Marc Avram, MD, a Manhattan hair transplantation specialist, told Elle Magazine, "As we get older, follicles shrink, producing skinnier, shorter strands; then the follicles start to die off. That rate and the extent of that process is a matter of genetics."

3. Pregnancy Some women experience hair loss with pregnancy or as part of post-pregnancy hormonal changes. Other women experience hair loss when going on or off (usually off) the birth control pill.

4. Illness or intense stress Sometimes hair loss occurs as a result of illness. Stress, excessive weight loss, iron deficiency and thyroid problems can also cause hair loss.

If you're really worried, ask your doctor, however, experts say you really only need to worry if your part is getting wider or you can see your scalp through your hair. For severe cases, you might consult a "trichologist," a physician who specializes in hair loss.

Extra tip: If you're a woman you won't experience male-pattern baldness. Women's hair tends to thin all over. The only FDA-approved hair loss treatment is minoxidil. Minoxidil works in 60-70 percent of cases by improving the follicle's ability to produce hair.