With age, white hair multiplies, both in women and men. This natural phenomenon, also known as canities, often raises many questions. Learn more about white hair, its origins, its peculiarities, and the various ways to respond to its appearance.
Understanding everything about white hair.
The hair pigmentation system, in brief.
The natural pigmentation of hair is primarily influenced by the proportion within hair fibres of two types of melanin: theeumelanin and the pheomelanin. These pigments are produced in melanocytes, specialised cells located at the base of hair follicles. Eumelanin is responsible for shades of brown and black, while pheomelanin gives hues of blonde, red and copper. The relative proportion of eumelanin and pheomelanin in the hair determines the final colour.
The production of melanin is regulated by a number of genes and environmental factors. The MC1R gene in particular plays a crucial role in determining hair pigmentation. Variations can lead to a reduced or altered production of melanin, which results in lighter hair colours, such as blonde or red. Once synthesised from tyrosine under the influence of tyrosinase, melanin is transferred to the keratinocytes, cells located at the base of the hair bulb and responsible for producing keratin. It's worth noting that keratin is the main component of hair (≈ 95%).
The causes of the onset of white hair.
The greying of hair is a natural process that typically begins around the age of 35. However, we are not all equal when it comes to the onset of white hair. Some people see their hair turn white as early as their twenties, while others still have naturally coloured hair into their fifties. The causes of white hair appearance are varied.
Most of the time, greying hair is due to the natural ageing of the body, which is accompanied by the gradual decrease in the number of melanocytes and their activity. Moreover, when a hair grows, hydrogen peroxide is released as a by-product. This is a reactive species that triggers a chain of reactions leading to the degradation of melanin. The hydrogen peroxide is normally eliminated by an enzyme called catalase, but this becomes increasingly scarce in cells over time, contributing to the onset of white hair.
The age at which our first grey hairs appear is largely dictated by genetics. Studies have shown that people of so-called Caucasian type generally see their hair turn grey in their early thirties, those of so-called Asian type notice it in their late thirties, and those of so-called African type see it during their forties. Several genes are involved, such as the MC1R gene, mentioned above, or the IRF4 gene. One or more mutations on these genes can accelerate or slow down the greying of hair.
Pollution, UV rays from the sun, and smoking exert oxidative stress on cells, leading to an excessive production of free radicals. These free radicals have the effect of degrading melanin, the pigment that gives hair its colour, through a series of reactions. Thus, oxidative stress promotes the appearance of white hair.
Some autoimmune diseases.
Vitiligo is an acquired autoimmune disease characterised by white patches on the skin (leucoderma) and depigmentation of hair or fur. It occurs when the immune system attacks the melanocytes, which then die or become unable to function.
Chronic stress can be a contributing factor to the early onset of white hair. Studies have suggested that prolonged exposure to stress can disrupt the functioning of melanocytes, the cells responsible for the production of melanin, thus leading to a decrease in hair pigmentation. The most well-known example is that of Marie Antoinette, whose hair is said to have turned white the night before her execution due to stress.
Some deficiencies in vitamins or nutrients.
Deficiencies in vitamin B12, vitamin D, vitamin B9, selenium, iron or copper can impact hair colour and cause premature greying. The mechanisms involved are diverse and depend on the nutrient in question. For instance, copper promotes the activity of tyrosinase, the enzyme that enables the conversion of tyrosine into melanin. Selenium and zinc, on the other hand, are antioxidants that protect melanin from free radicals.
The characteristics and peculiarities of white hair.
White hair exhibits a slightly different texture compared to other hair types and is more fragile and susceptible to external damage. This characteristic is due to the low amount of melanin in their cortex, the middle layer of the hair fibre. Indeed, melanin does not only play an aesthetic role, but it also protects the hair, particularly shielding it from oxidative stress caused by UV rays or pollution.
Furthermore, the sebum production by the sebaceous glands decreases over time. Sebum is a protective lipid film synthesised on the scalp's surface and then slides down the hair lengths and tips. It is crucial for maintaining the hydration of the fibres and their protection. The decrease in sebum synthesis explains why white hair tends to be drier and more fragile.
It is important to note that white hair sometimes tends to yellow. Several causes are put forward to explain this yellowing, among which is the oxidation of residual melanin. This oxidation leads to a change in the chemical structure of melanin, resulting in a yellow colour. All shades of hair can be affected by this phenomenon, but it is more visible on white hair, for colourimetric reasons. Indeed, if you add white and yellow, you get a yellowish colour, whereas if you add brown and yellow, you get more of a light chestnut.
White hair: a unique maintenance.
Due to their fragility, white hair requires special care. To compensate for the lack of melanin and the decrease in sebum synthesis, it is recommended to hydrate white hair regularly with a nourishing mask or vegetable oils. You can also turn to treatments specifically formulated for white hair if you wish. These could be, for example, purple shampoos, which are yellowing, or restorative conditioners.
We also recommend that individuals with white hairavoid using heat styling tools, such as straighteners or heated brushes. Being extremely delicate, they do not tolerate heat well. Similarly, it is important to protect white hair from the sun's UV rays, which generate oxidative stress. To do this, you can cover your hair with a hat, cap or scarf on particularly sunny days, or use a hair-specific sun protection product.
First white hairs: what to do?
Hair whitening is a natural phenomenon that affects everyone at some point in their life. There are several options when one discovers white hairs in their mane. The simplest is to accept them. It is then appropriate to manage the transition between coloured hair and white hair to avoid a too pronounced demarcation.
Some people have a more drastic reaction when they first see white hair and decide to pluck them out. Although plucking a white hair will not cause two to appear, contrary to popular belief, it is still an action that is not recommended as it is harsh on the scalp.
If your white hair bothers you, you can choose to conceal it by changing your hairstyle, strategically placing your strands, or even resorting to hair dye or highlights. If you opt for the latter, we advise you to consult a professional hairdresser as colouring hair is quite technical and it's not easy to do it yourself.
SEIBERG M. Age-induced hair greying - the multiple effects of oxidative stress. International journal of cosmetic science (2013).
RAWNSLEY J. & al. Hair Biology: Growth and Pigmentation. Facial plastic surgery clinics of North America (2018).
PHILPOTT M. Watching hair turn grey. eLife (2021).