Hair greying is a universal biological process that marks the natural aging of the hair follicle. While the loss of color is inevitable for most people, the age at which this change begins varies widely among individuals. This shift from pigmented to unpigmented hair is a gradual reduction in the color-producing capacity of the hair follicle, influenced by a complex interplay of genetic programming and external factors.
The Typical Age Range for Hair Greying
The onset of hair greying is highly dependent on an individual’s genetic background and ancestry. On average, individuals of Caucasian descent tend to begin greying in their mid-thirties, often around age 34, which is the earliest average onset among major ethnic groups. The average age for people of Asian descent to start noticing grey hair is slightly later, usually in their late thirties.
Individuals of African descent generally experience the onset of greying later than others, with the average age being in their mid-forties. This difference in timing is thought to be partly due to African hair samples having larger melanosome sizes and a higher density of pigment-carrying structures. Generally, by the age of 50, approximately 50% of people will have about 50% grey hair, regardless of their ethnic background.
These figures represent a statistical average, and individuals commonly fall outside these typical ranges. The process is usually gradual, with a mixture of pigmented and white hairs giving the appearance of “grey” or “salt-and-pepper” hair. Greying is typically seen first at the temples and sideburns before advancing to the crown and then the back of the scalp.
The Biological Mechanism of Color Loss
The color of a hair strand comes from melanin, a pigment produced by specialized cells called melanocytes residing in the hair bulb of the follicle. Melanocytes transfer this melanin into the keratinocytes, the structural cells that make up the hair shaft, effectively coloring the hair as it grows. The two types of melanin—eumelanin (black/brown) and pheomelanin (red/yellow)—determine the natural hair color based on their ratio.
Hair greying occurs when melanocytes progressively lose their ability to produce and transfer pigment into the hair fiber. This loss of function is linked to the depletion of melanocyte stem cells, which are the reservoir needed to replenish differentiated melanocytes at the start of each new hair growth cycle. As the stem cell pool diminishes, fewer active melanocytes are available to color the new hair.
A molecular factor in this process is the accumulation of hydrogen peroxide within the hair follicle, a byproduct of the melanin production process itself. Normally, the enzyme catalase breaks down this hydrogen peroxide into water and oxygen, but catalase activity decreases with age. The resulting high concentration of hydrogen peroxide acts as an oxidative stressor, bleaching the hair from the inside out and blocking the function of tyrosinase, the enzyme essential for melanin synthesis. The absence of pigment leaves the hair shaft colorless, causing it to appear white against pigmented hairs.
Genetic and Lifestyle Influences on Timing
While the underlying biological mechanism is constant, the pace at which melanocyte stem cells are exhausted is largely dictated by an individual’s genetic blueprint. Heredity is the strongest predictor of when an individual will begin to grey, meaning a person is likely to start greying around the same age their parents or close relatives did. Specific genetic variants, such as those in the IRF4 gene, have been identified as associated with the timing of hair greying.
Beyond inherited predisposition, various environmental and lifestyle factors can act as accelerators, influencing how quickly greying manifests. Chronic stress is one such factor, as severe, prolonged stress may lead to the premature exhaustion of melanocyte stem cells. This connection is thought to be mediated by the body’s stress response system, which can trigger inflammatory and oxidative pathways.
Smoking is another external factor linked to earlier greying, with studies showing that smokers have a higher risk of premature greying compared to non-smokers. Severe nutritional deficiencies can also impair melanocyte function, particularly a lack of copper (necessary for the tyrosinase enzyme) and Vitamin B12. While not the root cause of typical age-related greying, these deficiencies can hasten the onset of color loss.
When Greying Is Considered Premature
Hair greying is classified as premature when it occurs earlier than the established average for a person’s ethnic background. For individuals of Caucasian descent, greying is defined as premature if it begins before the age of 20. The threshold is slightly later for people of Asian descent (before age 25) and for individuals of African descent (before age 30).
While premature greying is often a benign, genetically determined condition, it can occasionally signal an underlying medical issue. Conditions that disrupt normal metabolic or immune function are sometimes associated with early greying. These include autoimmune disorders like vitiligo, where the immune system attacks pigment cells, and certain thyroid dysfunctions, such as hyper- or hypothyroidism.
Nutritional deficiencies, especially severe or chronic low levels of Vitamin B12, can also present with premature greying, sometimes linked to conditions like pernicious anemia. If greying occurs substantially outside the expected age range, particularly if accompanied by other symptoms, consulting a healthcare professional can help rule out treatable underlying health concerns.