The cause of hair loss include heredity, hormones, diet, stress, illness, and also poor hair care. Diet, Stress and illness are considered more temporary conditions and the hair loss usually can be reversed when the diet is improved, or when the anxiety inducing condition is reduced, the illness is cured, when hair care improves.
Hormones and heredity are a different matter than the temporary causes above. With heredity, the condition is not reversible, you are after all a product of your parents, and hair loss is no exception. Hormones on the other hand are a different story and they have varying and different effects on each person individually.
With men, the testosterone is abundant in the body. There is a substance produced from testosterone called DHT. This is well known to cause hair loss in men by shrinking the hair follicles. What happens is that the hair follicles shrink enough so that they are not able to product any hair. Then as the older hair dies off, no new hairs are produced to replace them.
In Women, a hormonal imbalance can be the cause of hair loss. Menopause, pregnancy and even childbirth can all significantly change hormonal levels in the body leading to both mental and physical effects. This can lead to hair loss either permanent or temporary.
Products used for hair regrowth and hair loss have been used for centuries. In the ancient times, many different herbal and oil based remedies were made by the American Indians, Aztecs, Mayans and Egyptians, all with varying degrees of effectiveness.
The modern medical research community has mainly focused on different ways to open or stimulate the semi dead hair follicles, allowing hair growth to occur naturally again, as well as keeping the normal hair follicles healthy. This has lead to many products being available, some you can get over the counter and others you will need a prescription.
There is one primary ingredient in many hair loss products and that is Minoxidil. There has been extensive research into this and it is shown to be about 80% effective at stopping hair loss and in some cases may even help to grow back some hair. The most well known product that contains this is probably Rogaine, available almost anywhere, and comes in types for men and women.
Another product that contains minoxidil is Provillus, and studies have shown that it is effective. Provillus is different from other similar products in that it has an added ingredient, Azelaic Acid; this seems to enhance follicle repair in men and women.