Armpit hair and pubic hair are the same type of hair. Both are classified as terminal androgenic hair, meaning they share the same biological origin, are triggered by the same hormones, and develop during the same stage of life. They aren’t identical in every detail, but biologically, they belong to the same category and serve similar functions.
Why They’re the Same Type of Hair
Your body has two main kinds of hair: fine, nearly invisible vellus hair (the peach fuzz covering most of your skin) and thicker, darker terminal hair. Before puberty, the hair follicles in your armpits and groin produce vellus hair. Once androgen levels rise, those follicles transform, producing the coarser, pigmented terminal hair you recognize as armpit and pubic hair.
This transformation is driven by the same hormones acting on the same type of androgen-sensitive follicles. Hair follicles in the armpits, pubic region, face, and chest are all subject to the stimulatory effect of androgens. The process is essentially identical in both locations: androgens bind to receptors in the follicle, the follicle enlarges, and the hair it produces becomes longer, thicker, and darker.
The Hormones Behind Both
The story starts with a process called adrenarche, which typically begins between ages 6 and 9. During adrenarche, the adrenal glands (small glands sitting on top of your kidneys) start producing more of a precursor hormone called DHEA. Your body converts DHEA into more powerful androgens, including testosterone. These androgens are what stimulate the growth of both pubic and armpit hair.
This is why pubic and armpit hair often appear around the same time during development, and why they sometimes show up together even in cases of early development. When a child develops pubic hair earlier than expected, armpit hair frequently appears alongside it, because both are responding to the same rise in adrenal androgens. Pediatricians recognize this pattern as premature adrenarche, a benign variation where adrenal androgen production simply starts earlier than average.
How the Timing Differs
Even though the same hormones drive both, pubic hair usually appears first. Most people notice pubic hair a year or two before armpit hair shows up. This is because the follicles in the pubic region are slightly more sensitive to low levels of androgens, so they respond earlier as hormone levels begin to climb. Armpit hair follicles need a somewhat higher androgen concentration before they make the switch from vellus to terminal hair.
There’s no standardized clinical scale for armpit hair development the way there is for pubic hair (which doctors track using the Tanner stages). This partly reflects how variable armpit hair growth is from person to person. Some people develop thick armpit hair quickly; others never grow much at all. The same variability applies to pubic hair, but it tends to follow a more predictable progression.
Where They Differ
Despite being the same hair type, armpit and pubic hair aren’t perfectly identical. The differences come down to the local skin environment rather than the hair itself.
- Texture and curl pattern: Pubic hair tends to be coarser and curlier than armpit hair. This is influenced by the shape of the follicle and the local skin structure, not by a fundamentally different kind of hair.
- Growth cycle: Both have relatively short growth phases compared to scalp hair, which is why they stay short without trimming. Pubic hair’s growth phase is slightly shorter, keeping it a bit more contained.
- Density and coverage: The pubic region generally has denser hair coverage, while armpit hair grows in a more confined patch. Hormonal sensitivity, follicle density, and genetics all play a role in these differences.
These are variations within the same hair category, not signs of fundamentally different biology.
They Serve Similar Functions
Both areas share a feature that most of your skin does not: apocrine sweat glands. These specialized glands are concentrated in the armpits and groin, and they secrete a complex mixture of substances through hair follicles. Unlike the eccrine sweat glands that cover most of your body and help regulate temperature, apocrine glands primarily serve a lubrication function. Their secretions may also function as pheromones, chemical signals that could play a role in social or sexual communication.
Hair in both regions likely helps with friction reduction, keeping skin-on-skin contact from causing irritation during movement. The hair also increases the surface area available for apocrine secretions to evaporate, which would amplify any scent-signaling role those secretions play. This shared anatomy reinforces that armpit and pubic hair evolved to fill the same niche in two different body locations.
Why the Confusion Exists
People tend to think of pubic hair as its own special category because of where it grows and the social meaning attached to it. But from your body’s perspective, the distinction is geographic, not biological. The hair follicles in your armpits and groin are responding to the same hormonal signals, undergoing the same transformation, and producing the same general type of hair. They look slightly different because of local skin conditions and follicle shape, the same way scalp hair can vary in texture depending on where on your head it grows.
If you’ve ever noticed that armpit and pubic hair feel similar, grow at similar rates, and appeared around the same point in your life, that’s not a coincidence. They’re the same kind of hair doing the same job in two different places.