Ingrown hairs happen when a hair curls back or grows sideways into the skin instead of rising straight out of the follicle. The result is a red, often painful bump that can look like a pimple. While anyone can get one, the underlying causes range from the physical shape of your hair follicle to how you remove hair to genetic factors that make some people far more prone than others.
How Hair Re-Enters the Skin
There are two distinct ways a hair becomes ingrown, and both start with the shape of the hair tip.
The first is called extrafollicular penetration. After a close shave, the emerging hair has a sharp, angled tip. If the hair is even slightly curly, it grows in an arc, and that sharp tip can pierce the skin a few millimeters away from the follicle opening. Dry shaving without any moisture tends to produce especially sharp, beveled tips that make this more likely.
The second mechanism is transfollicular penetration. This happens when the hair never actually leaves the follicle. If you stretch the skin tight while shaving, or shave against the grain, the hair gets pulled slightly before the blade cuts it. Once released, the shortened hair retracts below the skin surface. As it grows, the curved shaft pushes sideways into the follicle wall rather than traveling upward toward the surface. Multi-blade razors are particularly prone to causing this: the first blade lifts the hair while the second cuts it, pulling the remaining stub below skin level.
In both cases, once the hair tip punctures surrounding tissue, your immune system treats it like a foreign object. That triggers inflammation, redness, and the characteristic painful bump.
Why Curly Hair Is the Biggest Risk Factor
Hair follicle shape is the single strongest predictor of ingrown hairs. People with naturally curly or coiled hair have curved follicles, and the hair that grows from them follows that same curved path. Research on the genetics of ingrown hairs found that curly hair alone creates a more than 50 times higher risk of developing chronic ingrown hairs compared to straight hair. That curvature is what sends the growing tip back toward the skin rather than away from it.
This is why ingrown hairs disproportionately affect Black men. Between 45% and 83% of men of African ancestry experience chronic ingrown hairs in the beard area, a condition clinically known as pseudofolliculitis barbae. The curved follicle structure common in African hair produces tightly coiled strands that are far more likely to re-enter the skin after shaving. But curly-haired people of any background face elevated risk in any area where they remove hair.
The Genetic Component
Beyond hair texture, specific genetic variations independently increase your risk. Researchers identified a mutation in a gene called KRT75, which provides structural support to the inner lining of the hair follicle. People carrying this mutation have a six-fold increased chance of developing ingrown hairs, likely because the weakened follicle structure makes it easier for a growing hair to puncture through the follicle wall from the inside.
This mutation is about three times more common in African Americans than in Caucasians (roughly 37% versus 11%). In a study of 200 people, 35% of those with chronic ingrown hairs carried the mutation compared to just 9% of unaffected individuals. Importantly, curly hair and the KRT75 mutation are independent risk factors. You can have one without the other, and having both compounds the problem.
How Hair Removal Methods Contribute
Almost any form of hair removal can set the stage for ingrown hairs, but some methods are worse than others.
- Shaving creates a sharp, angled tip on every cut hair. Shaving too closely, shaving against the grain, or using multi-blade razors all increase the odds by either sharpening that tip further or pulling the hair below the skin surface before cutting.
- Waxing and tweezing remove the entire hair from the root. When the new hair grows back, it has to navigate the full length of the follicle to reach the surface. If the follicle is curved or the opening is blocked, the hair can get trapped underneath.
- Tight clothing over freshly shaved or waxed areas creates friction and presses emerging hairs flat against the skin, encouraging them to grow sideways rather than outward. This is especially common in the bikini area, underarms, and along the neckline.
Dead Skin and Blocked Follicles
Even a straight-growing hair can become ingrown if its exit is blocked. Dead skin cells naturally accumulate at the follicle opening, and if they build up enough, they form a plug that traps the hair underneath. The hair keeps growing but has nowhere to go, so it curls beneath the surface.
Hormones play a role here too. Androgens, the hormones responsible for stimulating thicker, darker body hair starting at puberty, also influence how quickly skin cells turn over around the follicle. Higher androgen levels can drive follicles to produce coarser hair while simultaneously making follicle openings more prone to blockage. This is one reason ingrown hairs tend to appear in hormone-sensitive areas like the beard, bikini line, and underarms, where androgens convert fine hairs into thicker terminal hairs.
Ingrown Hairs vs. Bacterial Folliculitis
Ingrown hairs and bacterial folliculitis can look nearly identical: both produce red, irritated bumps around hair follicles. The difference is what’s causing the inflammation. With an ingrown hair, the bump forms because the hair itself is trapped in the skin. With bacterial folliculitis, the follicle has been infected by bacteria (usually staph), and the hair may be growing normally.
A few clues help you tell them apart. Ingrown hairs often have a visible hair loop or dark spot beneath the skin surface. They cluster in areas you shave or wax. Bacterial folliculitis tends to appear as itchy, pus-filled bumps that can spread to follicles you haven’t disturbed at all, and it sometimes follows a cut or wound that let bacteria in. If your bumps spread, produce significant pus, or don’t improve after you stop shaving for a few weeks, a bacterial infection is more likely.
Reducing Your Risk
Since the core problem is a sharp hair tip meeting vulnerable skin, prevention focuses on softening one or both sides of that equation.
Shaving technique matters more than most people realize. Shaving with the grain instead of against it, using a single-blade razor, and avoiding pulling the skin taut all reduce the chance of the hair retracting below the surface. Wetting and softening the hair before shaving (warm water, shaving cream, or gel) produces a less jagged cut tip. Rinsing the blade after every stroke keeps it sharp enough to cut cleanly rather than tug.
Regular exfoliation helps keep follicle openings clear. Products containing glycolic acid or salicylic acid dissolve the dead skin cells that plug follicles and trap hairs underneath. Using a gentle scrub or chemical exfoliant on ingrown-prone areas two to three times a week can make a noticeable difference, especially between shaves. Benzoyl peroxide also helps by reducing bacteria in the follicle, which limits inflammation if a hair does become trapped.
For people with very curly hair who get ingrown hairs repeatedly, the most effective prevention is simply letting hair grow longer. Keeping beard hair at least 1 to 2 millimeters long prevents the sharp tip from reaching the skin surface. Electric trimmers that cut hair just above skin level rather than below it offer a middle ground between a close shave and a full beard. Laser hair removal and prescription creams that slow hair growth are longer-term options for persistent cases.