Puberty is a period of profound physical transformation, driven by an intense surge of hormones that signals the transition from childhood to adulthood. These internal shifts affect nearly every system in the body, and the hair is no exception. These modifications are directly linked to the body’s new hormonal environment, resulting in differences in texture, oiliness, and distribution.
The Hormonal Drivers of Hair Change
The biological foundation for hair changes during adolescence lies in the dramatic increase of sex hormones, primarily androgens like testosterone and its potent derivative, dihydrotestosterone (DHT). While often associated with males, androgens increase in all genders during puberty, just at different concentrations. Hair follicles are highly sensitive to these circulating hormones, which act as powerful signals for growth and change.
This hormonal action dictates the shift from vellus hair to terminal hair. Vellus hair is the fine, short, light-colored hair, or “peach fuzz,” that covers most of the body during childhood. Terminal hair is the thicker, longer, and darker hair that makes up the eyebrows, eyelashes, and scalp hair. During puberty, androgens cause many vellus follicles to deepen and enlarge, transforming them into follicles that produce terminal hair.
Transformation of Scalp Hair
The hair on the head is significantly affected by the hormonal environment of puberty, often leading to noticeable changes in texture and thickness. The increased level of androgens stimulates the sebaceous glands connected to the hair follicles. This stimulation results in an overproduction of sebum, the natural oil that lubricates the skin and hair.
This surge in sebum production often causes the scalp and hair to become noticeably oilier, sometimes requiring more frequent washing. This excess oil can also contribute to common teenage scalp issues like dandruff or seborrheic dermatitis, as it provides an ideal environment for naturally occurring scalp yeast to flourish. Beyond oiliness, the physical characteristics of the hair strand itself can change.
The shape of the hair follicle, which determines whether hair is straight, wavy, or curly, can be altered by hormonal influence. An increase in androgens may change a round follicle shape to a flatter, asymmetrical one, which can cause previously straight hair to become wavy or curly. Conversely, some individuals may experience a loss of curl.
The Emergence of Secondary Hair Characteristics
A hallmark of puberty is the growth of new hair in areas previously covered only in vellus hair. This secondary hair growth is directly stimulated by the increased sensitivity of specific follicles to androgens. The first of these new hair types to appear is often pubic and axillary, or armpit, hair.
This growth follows a predictable pattern of development, starting as sparse, light hair and gradually becoming coarser, darker, and more extensive as puberty progresses. In males, this process also stimulates the growth of facial hair, including beards and mustaches, and often increases the density and length of hair on the chest, back, and limbs. The specific distribution and amount of this new terminal hair are heavily influenced by genetics and the individual’s sensitivity to circulating androgens.
How Permanent Are These Changes?
For most people, the hair changes driven by the hormonal shifts of puberty are permanent, representing long-term biological changes. The transition of vellus hair into terminal hair on the body and the establishment of a new baseline texture on the scalp are usually retained. Once a hair follicle has deepened and converted to producing a terminal hair strand, it remains that way throughout adulthood.
Temporary issues like excessive scalp oiliness, which is a reaction to the initial hormonal surge, often decrease as the endocrine system settles into its adult rhythm in later adolescence or early adulthood. While the new hair is permanent, future hormonal events, such as pregnancy or menopause, can cause further texture changes later in life.