Bumps on the scalp are extremely common, and most turn out to be one of a handful of things: infected hair follicles, clogged pores, cysts, or an inflammatory skin condition. The cause usually depends on what the bumps look like, how they feel, how many there are, and how long they’ve been there. Here’s how to narrow it down.
Folliculitis: Infected Hair Follicles
The most common cause of small, tender bumps on the scalp is folliculitis, an infection of the hair follicles. These bumps typically look like tiny pimples, often with a visible white or yellow center of pus. They can itch, sting, or feel sore to the touch. Bacteria, particularly staph, cause most cases, but yeast and fungi can also be responsible.
Folliculitis tends to show up after things that irritate or trap moisture against the scalp: wearing tight hats for long periods, sweating heavily during exercise, or shaving the head. It can also develop after soaking in an improperly cleaned hot tub, in which case bumps usually appear one to two days after exposure. Mild folliculitis often clears on its own within a week or two if you keep the area clean and avoid further irritation. Stubborn or recurring cases may need a targeted treatment from a dermatologist to address the specific type of bacteria or fungus involved.
Scalp Acne
Scalp acne looks and feels a lot like facial acne: red bumps or whiteheads, sometimes painful, clustered along the hairline or scattered across the scalp. The underlying cause is the same, too. Hair follicles get clogged by a combination of oil, dead skin cells, and product buildup from things like gels, hairsprays, and heavy conditioners. Sweat and naturally occurring bacteria or yeast on the skin can make it worse.
If you suspect product buildup is the culprit, switching to oil-free, noncomedogenic hair products is the simplest first step. Washing your hair after workouts helps too, since sweat sitting on the scalp is a reliable trigger. For mild cases, an over-the-counter shampoo with salicylic acid (look for concentrations between 1.8 and 3 percent) can help unclog follicles and reduce inflammation.
Pilar Cysts
If the bump on your scalp is a single, firm, smooth lump that moves slightly under the skin and doesn’t hurt, it’s likely a pilar cyst. These are the most common type of cyst found on the scalp, affecting roughly 10 percent of the population. They grow from hair follicles and are filled with keratin, the same protein that makes up your hair and nails.
Pilar cysts feel like a marble under the skin. They’re flesh-colored, painless, and tend to grow slowly over months or years. Some stay pea-sized; others can eventually reach the size of a baseball, though that’s unusual. They’re benign and don’t require treatment unless they become bothersome, painful, or infected. If you want one removed, it’s a straightforward in-office procedure.
Sebaceous cysts can also appear on the scalp, though they’re less common there. The key difference: sebaceous cysts tend to be smaller, may have a tiny visible opening on top, and can ooze an oily substance if squeezed. Pilar cysts are smooth, closed, and firm.
Scalp Psoriasis and Seborrheic Dermatitis
Not all scalp bumps are individual pimple-like spots. If you’re feeling raised, scaly patches that are itchy or flaky, the cause is more likely an inflammatory skin condition. The two most common are scalp psoriasis and seborrheic dermatitis.
Both can cause red, flaky, raised areas on the scalp, but they look and behave differently up close. Psoriasis produces thicker, drier scales and tends to extend past the hairline onto the forehead, behind the ears, or down the back of the neck. Seborrheic dermatitis, which is essentially a more severe form of dandruff, produces thinner, greasier-looking scales that usually stay within the hair-bearing areas. Seborrheic dermatitis is driven partly by a yeast that lives naturally on the skin, which is why antifungal shampoos containing selenium sulfide (1 percent concentration) can be effective.
Both conditions are chronic, meaning they tend to flare and calm in cycles rather than disappearing permanently. Over-the-counter medicated shampoos can manage mild flares, while more persistent cases may need prescription-strength treatment.
Signs a Bump Could Be Serious
The vast majority of scalp bumps are harmless, but skin cancer can develop on the scalp, and it’s easy to miss because hair covers the area. Basal cell carcinoma, the most common type of skin cancer, can appear as a shiny, slightly translucent bump that looks pearly white or pink on lighter skin, or brown to glossy black on darker skin. You might notice tiny blood vessels running through it.
The biggest red flag is a sore or bump that doesn’t heal. A growth that bleeds, scabs over, then bleeds again over the course of weeks is worth getting checked. The same goes for any lesion with an irregular border, a white waxy or scar-like appearance, or dark spots within it. These features don’t automatically mean cancer, but they do warrant a dermatologist’s evaluation, especially in sun-exposed areas like the part line or the crown of the head in people with thinning hair.
What’s Causing Yours
A few quick questions can help you sort through the possibilities:
- Multiple small, pus-filled bumps: Most likely folliculitis or scalp acne, especially if they appeared after sweating, using a new product, or wearing headgear.
- A single firm, painless lump under the skin: Probably a pilar cyst, particularly if it’s smooth and has been there for a while.
- Raised, scaly, itchy patches: Points toward psoriasis or seborrheic dermatitis, especially if you have similar patches elsewhere on your body.
- A bump that bleeds, won’t heal, or looks shiny and translucent: Should be examined by a dermatologist to rule out skin cancer.
For mild, short-lived bumps, simple adjustments like switching hair products, washing more frequently after sweating, and using a medicated shampoo are reasonable first steps. Bumps that persist beyond a few weeks, keep coming back, or change in size, shape, or color are worth professional evaluation. A dermatologist can usually identify the cause by examining the scalp and, if needed, taking a small tissue sample to get a definitive answer.