Every strand of hair on a human head is genetically programmed to a cycle that includes growth, stabilization, aging and shedding. On average, every day a human head sheds about 50–125 hairs (depending on sex), but most of them will come back after the resting stage as the follicle itself is not destroyed. Trouble begins when the loss exceeds re-growth, or the re-growth is weak and unhealthy.
The hair follicle cycle is a complex process and entails involvement of cell differentiation, epithelial–mesenchymal interactions, stem cell augmentation, pattern formation, apoptosis (programmed cell death), cell and organ growth cycles, and pigmentation.
Normal hair follicles cycle between a growth stage (anagen), a degenerative stage (catagen), a resting stage (telogen) and a shedding stage (exogen). The scalp hairs have a relatively long life cycle: the anagen stage ranges from 2 to 5 years, the catagen stage ranges from a few days to a few weeks, and the telogen stage is approximately 3 months. Hair cycle disturbances have dramatic effects on visible hair growth.
An analysis of hair shows that it is composed of iron, oxygen, hydrogen, nitrogen and sulphur. The blood must be supplied with these minerals so that nourishment will be carried to the scalp. Angiogenesis, the formation of new blood vessels from the pre-existing vascular network, is a driving force of hair growth. Using ingredients like camphor or menthol, that have been shown scientifically to increase blood circulation, will help promotion of hair growth at the vessel level. Prohibere has menthol and camphor so its possible the product may help promote hair growth but there is no data available to support that. It costs a lot of money to do a study.
Hair loss has been correlated to vitamin deficiencies (vitamin B especially). So what nutrients should we all be taking (but probably don't)?