Is white hair genetic?

While the age at which the first grey hairs appear varies from person to person, everyone notices a few white strands hidden in their hair at some point. From a biological perspective, several mechanisms are at work. The greying of hair is primarily due to a decrease in activity and number of melanocytes, the cells that synthesise melanin. This melanin is then transferred to the keratinocytes, the cells surrounding the dermal papilla of the hair follicle. The distribution of melanin within the keratinocytes determines the colour of the hair. In the absence of melanin in its cortex, the hair grows white.

This is compounded by a gradual decrease in the rate of catalase within the cells of the scalp. Catalase is an enzyme that breaks down certain reactive oxygen species, such as hydrogen peroxide, before they trigger melanin destruction processes. Less catalase means less protection for hair pigmentation.

Can the mechanisms described above be linked to genetics? Studies have investigated this question and the consensus is: white hair is, at least in part, genetic. Among other findings, they have shown that individuals of so-called Caucasian type generally see their hair turning white in their early thirties, those of so-called Asian type notice it in their late thirties, and those of so-called African type observe it during their forties.

Several genes have also been identified as being involved in the early onset of white hair, such as the MC1R gene (MelanocortinCortin 1 Receptor). Located on chromosome 16, it is a key gene in hair pigmentation. It codes for a membrane receptor protein primarily expressed in melanocytes. Indeed, when the α-melanocyte-stimulating hormone (α-MSH) binds to this receptor, it triggers a cascade of reactions within the cell, leading to the production of melanin.

A genetic mutation in the MC1R gene can influence the functionality of the receptor protein and thus the synthesis of melanin. This typically results in a light hair colour, such as blonde, red, or light brown. Furthermore, certain alleles of the MC1R gene are associated with a heightened risk of premature greying. Studies have shown that certain MC1R mutations are more frequently present in individuals who have grey or white hair before the age of 30.

One might also consider the IRF4 gene, located on chromosome 6 and coding for a protein known as Interferon Regulatory Factor 4. This plays a role in the regulation of transcription, that is, the process that allows genetic information to be used to produce proteins.

With regards to hair pigmentation, the IRF4 gene is involved in the regulation of melanin production. Studies have shown that specific genetic variations of the IRF4 gene can influence the timing of the onset of grey hair. The exact mechanism by which the IRF4 gene influences hair greying is not yet fully understood. However, it is suggested that the IRF4 gene could affect the differentiation and function of melanocytes, which would result in premature hair greying.

• RAWNSLEY J. & al. Hair biology: Growth and pigmentation. Facial Plastic Surgery Clinics of North America (2018).

• ARUNKAJOHNSAK S. & al. A review of the etiologies, clinical characteristics, and treatment of canities. International Journal of Dermatology (2019).