People often joke about whether they're having a good or bad hair day. The very concept of the "bad hair day" speaks to the role hair plays in many people's self-esteem. This emphasis on hair in society is one reason why the market for hair loss products, even unproven ones, is so huge: Many people are desperate to prevent further hair loss and re-grow their hair.

Only two products: minoxidil (Rogaine®) and finasteride (Propecia®) have been approved by the Food and Drug Administration (FDA) for hair loss. But it seems like hundreds of products, including shampoos, hair sprays and vitamins, are said to play a role in preventing hair loss and/or re-growing hair. People eager for an easy hair loss solution are often willing to give these products a try, and others may want to supplement their use of minoxidil or finasteride. Regardless, people are likely to wonder whether there is any research to support the claims of these other products, or if they're just quackery.

One of the reasons hair loss products can confuse consumers is that shampoos, for example, can be considered both cosmetics and drugs; the definition depends upon the product's intended use. If a product is marketed to improve appearance, it is regulated by the Federal Trade Commission, which enforces consumer protection laws. If a manufacturer claims that their product can re-grow hair, it should be considered a drug. While there is no approval process for cosmetics, the FDA has a rigorous drug approval process.

A number of shampoos and conditioners, such as Thicker, Fuller Hair Shampoo and Progaine 2-in-1 Shampoo/Conditioner, are marketed as cosmetics. Their manufacturers claim that they build body and create thicker hair. Jerome Shupack, MD, a dermatologist at New York University, says that these shampoos can indeed improve the hair's appearance. "The appearance of hair density is in part determined not just by the number of hair by the thickness of the hair shaft, which is determined by the size of the follicle," he says. "But if you increase the diameter of the hair shaft by 20 percent, then the overall density of the hair will appear to increase 20 percent." Dr. Shupack explains that hair-thickening shampoos increase the hair shaft size by using ingredients such as collagen, which temporarily adhere to the hair shaft.

Other hair products are said to create a scalp environment that is ideal for hair growth. For example, Nioxin, the manufacturer of a product line known as Semodex, claims that Semodex products help inhibit the infestation of demodex, a microscopic organism that lives in scalp. It's theorized that demodex causes inflammation that leads to a shortened hair cycle and results in hair loss. A study conducted in collaboration with Tulane University in New Orleans found that people with thin hair had higher levels of demodex than people with thicker hair.

Larry Millikan, MD, professor and chairman of dermatology at Tulane, emphasizes that the university did not participate in studies of Nioxin's impact on demodex. "Nioxin advertises as if we gave [Semodex] the seal of approval," he says. "But although they approached us about the study, it had nothing to do with their product."

The manufacturers of other products claim that their products can prevent hair loss and/or re-grow hair. Nano Shampoo, formulated by Peter Proctor, MD, PhD, contains nicotinic acid N-Oxide, which he describes as a minoxidil-like hair growth stimulator. And Revivogen is a topical product, sold with a shampoo, which is advertised as producing a significant decrease in hair loss after about four to five weeks and "revitalized" hair after three to four months. Revivogen has a number of ingredients that studies conducted in the test tube—as opposed to in animals or humans—suggest may stimulate hair growth. Additionally, Revivogen contains grape seed extract, which has been shown to stimulate hair growth in rodents. According to the Revivogen manufacturer, an independent researcher has started a study that will compare their product with a placebo, but did not indicate what institution was conducting the study.

Some shampoos contain Biotin, a part of the vitamin B-complex that is known as the "hair-and-nail vitamin." Biotin vitamins are also sold as hair products. Howard Baden, MD, professor of dermatology at Harvard University Medical School, argues that Biotin is also useful in those with Biotin deficiencies but will simply be excreted by people with normal levels of Biotin.

Experts say the claims associated with these products sometimes go too far. "There are only two things that will help hair loss: minoxidil and Propecia," Dr. Baden says. "Some products may make your hair look better, but they are not going to have any effect on retaining hair or producing growth of hair."

Both Drs. Baden and Shupack say they do sometimes recommend cosmetic products, such as sprays that help conceal the scalp and make the hair look thicker. Some of their patient use Toppik, a product available in different hair colors that contains keratin fibers that stick to the hair shaft.