Arginine, the power of this amino acid against hair/lash loss.

Comprised of over 80% keratin, hair and fur develop within hair follicles before growing and shedding. On average, each hair follicle undergoes between 25 and 30 cycles throughout its lifespan and we lose between 50 and 150 hairs per day. A greater loss can be explained by seasonal changes, hormonal shifts, pregnancy, or even stress. There are three stages in the life of a hair:

• The anagen phase : this is the growth phase of the hair. It lasts for two to five years. The synthesis and pigmentation of the hair shaft only occur during this phase. On average, a hair grows one centimetre per month.

• The catagen phase: this marks the end of fibre production. The follicle then retracts to the surface of the scalp. Also known as the "involution phase", this resting period typically lasts for two to three weeks.

• The telogen phase: During the telogen phase, the hair no longer grows but remains attached to the hair follicle. After approximately three months, the hair falls out and detaches from the hair follicle, which has already begun to produce a new hair.

The arginine is an amino acid renowned for its strengthening properties and its ability to stimulate the growth of hair and eyelashes. First isolated in 1886 by the German chemist Ernst SCHULZE and his assistant Ernst STEIGER, it is involved in various biological processes such as the regulation of cell division, facilitating the healing process and the proper functioning of the immune function. Naturally present in the body, arginine is also added to several cosmetic formulations intended for thin, fragile hair or those seeking growth.

A recent study has highlighted a link between an arginine deficiency and androgenetic alopecia. Indeed, it appears that the latter could be associated with a reduced expression of the arginine transporter SLC7A1, thus leading to a lower availability of this amino acid. Furthermore, an arginine deficiency can hinder the growth of hair and eyelashes by antagonising the mTOR signalling pathway. Therefore, the external supply of arginine emerges as a promising treatment strategy.

Murine models have also demonstrated that the administration of arginine can protect against theinhibition of hair growth induced by dihydrotestosterone (DHT), a hormone found in both men and women. DHT acts on hair follicles by shortening the lifespan of hair and eyelashes and accelerating hair cycles. By preventing it from exerting its suppressive activity, arginine has a beneficial effect on growth.

Arginine also has an effect on the Vascular Endothelial Growth Factor (VEGF) and enhances its activity in hair follicles. Primarily known for its role in promoting angiogenesis, this protein also plays a significant part in the growth process of hair and eyelashes. Indeed, by increasing angiogenesis, VEGF allows for the development of a more efficient vascular system, which results in a better supply of nutrients and oxygen to the hair follicles during the anagen phase.

Key Takeaway : Arginine appears to be a real ally in combating hair and eyelash loss.