Yes, red hair can naturally turn brown over time, a common occurrence rooted in the biology of pigment production. Red hair is defined by a high concentration of the reddish-yellow pigment pheomelanin and low levels of the dark pigment eumelanin. This gradual color change is a developmental process where the body begins to produce more of the darker pigment. The transition reflects the interplay between an individual’s genetics and their maturing physiology.
The Genetic Basis of Red Hair
The presence of red hair is strongly linked to variations in a single gene, the Melanocortin 1 Receptor gene, or MC1R, located on chromosome 16. This gene provides instructions for making a protein that controls which type of melanin is produced by specialized cells called melanocytes. When the MC1R receptor is fully functional, it signals the melanocytes to produce the dark brown or black pigment known as eumelanin.
In individuals with red hair, the MC1R gene contains variants that reduce the receptor’s ability to signal for eumelanin production. Because the signaling pathway for dark pigment is impaired, melanocytes primarily produce the reddish-yellow pigment, pheomelanin. This imbalance results in the distinct range of red hues, from strawberry blonde to deep copper.
Developmental Timeline of Hair Color Change
The natural darkening of red hair to brown or auburn shades typically aligns with two major phases of human development. The first common period is during infancy and early childhood, often before the age of ten, when very light hair colors begin to darken as the body matures.
The second, and often more dramatic, shift occurs around puberty, a time of significant hormonal fluctuation. Hormones regulate pigment-producing cells in the hair follicles, and the surge during adolescence can stimulate a change in color production. This color shift is a slow transition where new hair growing from the root contains more pigment, gradually replacing the lighter hair shafts.
Why Eumelanin Production Increases
The underlying reason for red hair darkening is the body’s increasing capacity to produce eumelanin as it develops. Although the genetic variants in the MC1R gene impair the production of dark pigment, they do not always completely eliminate it. As a person matures, their melanocytes may become more efficient at producing the small amount of eumelanin that their genetics allow.
The total amount of pigment deposited into the hair shaft increases as a child moves into adolescence and early adulthood. Even a modest increase in eumelanin production has a significant visual impact because eumelanin, the brown/black pigment, is chemically dominant over pheomelanin. The increased concentration of brown pigment effectively masks the red pigment, causing the hair to appear dark brown, auburn, or a rich reddish-brown.
This shift is a matter of changing ratios and total pigment load within the hair follicle. The hair is not losing pheomelanin, but the relative proportion of the darker eumelanin is increasing. The final color is a combination of these two melanin types, with the brown and black shades prevailing once their concentration reaches a certain threshold.
Environmental Influences on Hair Color
While the permanent shift from red to brown is a genetic and developmental process, external factors can temporarily alter the appearance of red hair. The most common environmental influence is exposure to ultraviolet (UV) radiation from the sun. Sunlight breaks down the melanin pigments within the hair shaft, causing the color to lighten or fade over time. For redheads, sun exposure often results in a brassy or bleached-out appearance on the length of the hair, rather than a natural darkening.
Other factors, such as chlorine, salt water, and certain pollutants, can also interact with the hair shaft’s surface, leading to minor color changes or fading. However, these external effects are limited to the existing hair strand and do not impact the melanocytes at the root. Therefore, any natural, permanent shift to a darker shade occurs because of internal biological changes, not external environmental damage.