Hair texture is defined by three primary characteristics: its curl pattern, the diameter of the individual hair strand, and the overall density of the hair on the scalp. Hair texture frequently shifts during the maturation process known as puberty. This common phenomenon is a direct result of biological changes that permanently alter the growth environment of the hair follicle. Understanding the mechanism involves examining the powerful chemical messengers that flood the body and the physical structure of the follicle itself.
Hormonal Drivers of Hair Change
The onset of puberty is marked by a significant increase in sex hormones, which act as the primary chemical triggers for hair changes throughout the body. The most influential group of hormones are the androgens, which include testosterone and its more potent derivative, dihydrotestosterone (DHT). These hormones increase substantially in both individuals assigned male and female at birth, although the resulting levels differ significantly.
Androgens exert their effect by binding to specialized receptors located within the dermal papilla, a cluster of cells at the base of the hair follicle. This binding initiates a signaling cascade that programs the hair follicle to change its function. The follicle is signaled to transition from producing fine, light vellus hair to generating thicker, darker terminal hair, which accounts for the development of pubic and underarm hair. On the scalp, this hormonal surge influences the hair’s growth cycle and physical characteristics, making the resulting hair strands different from those grown during childhood.
How Follicle Structure Determines Texture
The physical shape of the hair strand is determined by the shape of the hair follicle from which it grows, a structure embedded beneath the skin’s surface. A follicle that is perfectly round in cross-section produces straight hair, as the keratin protein is laid down symmetrically. Conversely, a follicle that is oval or elliptical forces the keratin to be deposited unevenly, creating a curve in the hair strand.
The more elliptical the follicle becomes, the curlier the resulting hair will be. During the surge of androgens at puberty, the hormonal signals can permanently alter the structural shape of the hair follicle duct. This change causes a previously round follicle to become more oval, which is the physical mechanism that translates hormonal changes into a new curl pattern. Since the follicle shape is permanently modified, the new hair texture established during this period is generally considered the adult pattern.
Common Texture Shifts Observed
The most noticeable texture shift experienced by adolescents is a change in the curl pattern, often manifesting as straight hair becoming wavy or curly, or wavy hair transitioning to a tighter curl. Less commonly, hair may also become straighter, depending on the individual’s genetic sensitivity to the changing hormone levels. Beyond the curl pattern, the diameter of the hair strand frequently increases, resulting in hair that feels coarser or thicker than it did in childhood. This shift in hair thickness is another indicator of the follicle’s response to androgens, which stimulate the production of a larger, more robust hair shaft.
Hormonal stimulation also causes sebaceous glands to become hyperactive, leading to an increase in sebum production. This results in hair that is noticeably oilier at the scalp, requiring adjustments to the individual’s hair care routine.