Many people's first reaction to the realization that they are losing their hair is denial. After all, who wants to face what is often the first sign of aging, not to mention a loss of a feature that is generally considered key to one's attractiveness? Not surprisingly, experts say that denial, which is often followed by months or years of fretting and inaction, is precisely the wrong reaction. It's recommended that both women and men seek treatment as soon as they notice hair loss.

"Usually, once you see hair thinning, you've already lost 50 percent of your hair," says Neil Sadick, MD, a clinical professor of dermatology at Weil Medical College of Cornell University in New York City. "Although the speed of hair loss progression varies, the earlier people get treated, the better."

In general, male- and female-pattern baldness, also known as genetic hair loss, begins later in women than in men. While it tends to start in the 30s or 40s in males, it begins in the 40s or 50s in women, though it can occur at any time after puberty in both sexes. According to Dr. Sadick, hair loss is actually as common in women as it is in men, though more severe in men. The patterns of hair loss are also different: Men tend to lose hair in the front and in the "monk's cap" area at the top of the head, while women experience more diffuse thinning throughout the scalp.

For women particularly, one major reason to see a hair loss specialist is to rule out causes of hair loss other than pattern baldness. "When women see hair loss, they should talk to a dermatologist immediately because the reason for it might demand a medical work-up and a solution to that problem," explains Joseph P. Bark, MD, a dermatologist in private practice and the past chair of dermatology at St. Josephs Hospital in Lexington, Kentucky.

According to Dr. Bark, a common cause of hair loss in women is hormonal: it's generally either due to going on or off birth control pills or the end of pregnancy. Both can cause telogen effluvium, a generally reversible form of hair loss that occurs when hair goes into a resting phase. "Pregnancy locks hair into a long growth phase," Dr. Bark says. "This ends at delivery, at which time point the hair thinks it's time to fall out. Women can shed between 20 percent and 30 percent of their hair starting several months after delivery, but it will start growing again."

Other potentially treatable causes of hair loss include thyroid problems, anemia, lupus and the excess production of androgen hormone. Hair loss can be a side effect of medications such as ibuprofen, antidepressants, hypertension drugs, anticoagulants and chemotherapy. And any shock to the system, such as weight loss or gain, or emotional stress, can trigger a hair-resting phase. All of these sources of hair loss cannot only cause shedding and thinning if uncorrected, but may also accelerate the progression of underlying female-pattern hair loss.

Once these causes have been eliminated and genetic hair loss has been established, hair loss specialists can begin treatment for female pattern hair loss. The only drugs approved by the Food and Drug Administration for hair loss are Rogaine (minoxidil), used in men and women, and Propecia (finasteride), approved only for men but sometimes used in postmenopausal women. Generic minoxidil, which is also sold under the brand name Rogaine, is available over-the-counter in 2 percent and 5 percent concentrations. Propecia is only available by prescription.

Both of these medications are most effective early in the hair loss process. "Rogaine and Propecia hang onto hair better than they produce it," Dr. Bark says. For example, Propecia maintains hair almost 90 percent of the time, but only re-grows significant amounts of hair in perhaps 40 percent of men.

Hair transplantation, which involves grafting hair follicles from one site on the head to another, should be considered when hair loss is significant and medical therapy options have been exhausted. Some experts say that surgery is often viewed by people with hair loss as a quick fix; they don't realize that a small procedure performed too early may lock them into a series of surgeries as their hair loss progresses and leave them with a pattern that may not be appropriate as they mature. The good thing, however, is that a properly timed and skillfully executed hair transplant can look very natural.