Hair Pigmentation

Hair pigmentation refers to the biological process that determines whether your hair appears blonde, brown, red or black — and why that colour can change throughout your life. Behind every shade lies the production of melanin in the hair follicle, driven by genetic predisposition, hormones and external influences. When you notice your hair becoming duller, turning grey more quickly or showing uneven discolouration, you are in fact seeing a shift in melanin production or its distribution. Understanding how this mechanism works allows you to take a more realistic view of what hair care, colour treatments and potential medical options can and cannot achieve.

How does pigmentation in hair develop?

Hair colour forms in the hair root, before the hair even becomes visible. Within the hair follicle are melanocytes: pigment cells that produce melanin and transfer it to the keratinocytes that make up the hair fibre. There are broadly two types of melanin: eumelanin (brown to black) and pheomelanin (red to yellow). The quantity and ratio between the two determine the final colour, as well as the optical depth. Dark hair typically contains more eumelanin and absorbs more light as a result, while light hair contains less pigment and reflects more light instead.

It is important to understand that pigmentation is linked to the growth phase of the hair. During the anagen phase — the period of active growth — pigment is incorporated into the hair fibre. In the resting and shedding phases, this supply stops. Once a hair has grown out of the skin, it no longer produces new pigment; the colour you see is, in a sense, fixed. Hair care can influence shine and tone, but it does not change the pigment production in the hair root itself.

Why does hair colour change over the years?

Many people notice that childhood hair darkens during puberty, or that brown hair can appear warmer or ashier with age. This is because the activity of melanocytes and the hormonal environment changes. Puberty, pregnancy, thyroid changes and certain medications can influence the pigment balance, causing the ratio between eumelanin and pheomelanin to shift subtly. Hair structure also changes with age: a coarser or drier hair fibre reflects light differently, meaning the same amount of pigment can give a different impression.

Hair can also appear lighter without less pigment having been produced in the root. UV light breaks down pigment in the hair fibre, especially when the hair is more porous due to chemical treatments or frequent heat exposure. This is often seen as sun-induced discolouration, where the ends are lighter than the roots. This is not about new pigmentation, but about pigment loss along the lengths.

Going grey: what happens to melanin?

Grey hair occurs when melanocytes in the hair follicle produce less melanin or eventually stop functioning. The hair then grows from the skin with little to no pigment. "Grey" is usually not a uniform colour, but a mixture: some hairs remain pigmented, while others are white and therefore completely pigment-free. Because white hair reflects light strongly, the overall appearance looks silver or grey, depending on the distribution. How quickly this process occurs varies greatly from person to person and is largely genetically determined.

Stress is often cited as a cause. Under exceptional, acute stress, the body can influence processes linked to stem cells and pigment cells, but in practice, heredity is usually the most important factor. Deficiencies, such as vitamin B12 or iron, can affect hair condition and sometimes pigment processes as well, but they do not account for the majority of cases. With sudden or striking changes, it is advisable to rule out medical causes, especially when hair loss or skin complaints are also present.

External influences: sun, styling and chemicals

Hair can become discoloured through oxidation and UV damage. Sunlight breaks down melanin, while chlorine and salt water can accelerate this process and roughen the hair fibre, causing pigment to disappear more quickly. Heat from a hair dryer or straightener can also cause colour changes, particularly with dyed or bleached hair, as the protective layer of the hair fibre is more easily damaged. The result is often dullness, a warmer glow (coppery or orange) or a grey haze in porous hair.

Chemical treatments directly affect pigment. Bleaching removes melanin from the hair fibre through oxidation, while permanent colouring adds colour molecules that bind to the fibre. In everyday language, "pigmentation" can therefore also refer to the visible colour in the hair. If colour fades quickly, it is usually due to porosity: a damaged hair fibre holds pigment less effectively. With care that offers UV protection, gentle cleansing and reduced heat, you can primarily keep existing colour stable for longer.

What can you do about pigment loss or thinning hair?

When colour loss is caused by sun or styling, the focus is mainly on protection and restoration. Think of a leave-in product with a UV filter, limiting heat exposure and thoroughly rinsing hair after swimming. With greying, it is more often a matter of acceptance or cosmetic choices, such as colouring or using toners. If a pigment change coincides with thinning hair or a more visible scalp, there may be more at play than colour alone. Fewer hairs per square centimetre makes the scalp more visible, which can make the overall appearance seem lighter, even if the pigment per hair has barely changed.

When hair loss or persistent thinning is a primary concern, a medical assessment can help to discuss causes and treatment options. In some situations, a hair transplant may be an option to restore density; the colour of the transplanted hair generally follows the characteristics of the donor area. Pigmentation is not "switched on" by this, but a better distribution of hair can reduce the visual impact of colour differences or greying.

Hair pigmentation shows how closely biology and appearance are intertwined. Melanin determines the shade, but age, hormones, sunlight and the condition of the hair influence how that shade ultimately looks. Understanding the changes — from discolouration along the lengths to the onset of grey — allows you to make more informed choices about protection, a colour treatment or a medical route when thinning is also a factor.