Children with blonde hair often see their locks turn brown or black over time due to genetic signals and hormonal surges, according to a report by science news outlet Live Science.
The dramatic shift in hair color is caused by changes in biological pigment production inside hair follicles. In early childhood, these follicles produce unstable levels of pigment before genes establish a permanent shade.
Hair color is determined by melanin, a biological pigment produced in hair follicles. Melanin is divided into two types: dark eumelanin and light-red pheomelanin. As the human body generates higher amounts of dark eumelanin, hair color becomes richer and deeper.
Desmond Tobin, a professor of dermatology at University College Dublin in Ireland, emphasized that everything depends on genetic inheritance.
Hormonal changes during puberty
The darkening process becomes most noticeable during adolescence, roughly between the ages of 10 and 13. During this stage of development, sex hormones such as estrogens and androgens switch on and prompt hair follicles to secrete larger quantities of dark pigment.
Individuals who remain blonde for life are simply genetically programmed for minimal secretion of dark pigment. Estrogens and androgens are primary sex hormones that regulate cellular functions and physical development as children grow into adulthood.
DNA variations and future research
Scientists have yet to determine the exact chain of chemical reactions involved in hair darkening. Wojciech Branicki, a human pigmentation researcher at Jagiellonian University in Krakow, Poland, suggested that the bodies of two children may react differently to hormonal changes because of differences in their DNA.
In some children, follicles begin producing pigment in massive amounts, while in others, follicles remain indifferent to the hormonal shifts. Branicki noted that research into human genome variations has advanced significantly, but scientists have not yet explained all aspects of the process.
Jagiellonian University, established in the 14th century, is one of the oldest universities in Central Europe and a major center for biological research.
