Hair loss is a genetic/hormonal process that can affect both men and women. Hormones that bind to hair follicles can cause an imbalance in the biological processes that cause hair growth. Eventually, excess hormones on the follicle cause hair to stop growing and the follicle dies.
Shampoo, wigs, creams, pills, powders, and just about anything else you can imagine has been marketed as a hair loss product. Hair loss products, if they are at all serious, work by either promoting hair growth, reducing the amount of hormones in the body, reducing inflammation at the follicle, or handling the autoimmune response that occurs as a result of too many hormones at the follicle site.
Hundreds of thousands of hair loss products are on the market today and only some are regulated and proven to actually be effective in helping prevent hair loss. It is important that you consult a dermatologist for a complete diagnosis and treatment options before using any product claiming to "cure" or stop hair loss. Some products can end up doing more harm than good.
A well-known product for hair-loss is Rogaine, a shampoo that works by promoting hair growth and retarding hair loss. Another product taken orally is Propecia, which works at the hormonal level to stop binding at the follicle site.