Bumps on the scalp are usually caused by clogged or infected hair follicles, but they can also result from cysts, inflammatory skin conditions, or (less commonly) skin cancer. Most scalp bumps fall into a few well-defined categories, and the type of bump you’re dealing with depends on what it looks like, how it feels, and how long it’s been there.
Folliculitis: The Most Common Cause
Folliculitis is inflammation of one or more hair follicles, and since your scalp has tens of thousands of them, it’s one of the most bump-prone areas on your body. The bumps typically look like small, red, pus-filled pimples clustered around individual hairs. They’re often itchy and tender to the touch.
The most frequent culprit is Staphylococcus aureus, a bacterium that lives on everyone’s skin and normally causes no harm. When it enters a damaged or irritated follicle through a scratch, tight hat, or razor nick, it can trigger an infection. Fungal folliculitis, caused by a type of yeast, produces a similar-looking rash of itchy, pus-filled bumps. This yeast-driven version is sometimes mistaken for bacterial folliculitis, but it won’t respond to antibiotics.
Damaged hair follicles are especially vulnerable. Anything that creates friction or micro-injuries on your scalp (helmets, headbands, frequent shaving) opens the door for bacteria, fungi, or viruses to move in and cause trouble.
Scalp Acne and Product Buildup
If the bumps on your scalp look and feel like regular pimples, you may be dealing with scalp acne. This happens when hair follicles get clogged by a combination of oil, dead skin cells, and hair product residue. Shampoos, gels, hairsprays, and leave-in conditioners can all leave a film that blocks follicles over time.
Oil-based and greasy styling products are the worst offenders. The buildup creates a plug in the follicle, trapping bacteria underneath and producing the same kind of red, raised bumps you’d see on your face or back. Switching to oil-free, noncomedogenic hair products and washing your scalp thoroughly can often clear mild cases without any other treatment.
Pilar Cysts
Pilar cysts are firm, round, smooth bumps that form just beneath the skin of the scalp. They develop from the outer lining of the hair follicle and are filled with a thick, white material made of keratin, the same protein in your hair and nails. Unlike pimples, they aren’t red or painful in most cases. They feel like a marble or pea rolling under the skin when you press on them.
These cysts grow slowly and can stay the same size for years. Most are small, but in rare cases a variant called a proliferating pilar cyst can grow much larger, sometimes reaching several centimeters. Pilar cysts tend to run in families and are more common in women. They’re benign, but if one becomes inflamed, infected, or bothersome, it can be surgically removed.
Seborrheic Dermatitis and Psoriasis
Both seborrheic dermatitis and scalp psoriasis can produce raised, scaly patches that feel like bumps when you run your fingers through your hair. The two conditions look similar enough that even dermatologists sometimes have to examine them closely to tell them apart.
Seborrheic dermatitis produces greasy, yellowish scales and tends to stay within the hairline. It’s driven by an overgrowth of a natural yeast on the skin, and it flares with stress, cold weather, or infrequent washing. This is the more severe end of what most people call dandruff.
Psoriasis produces thicker, drier, silvery-white scales and often extends past the hairline onto the forehead, behind the ears, or down the back of the neck. If you notice similar patches on your elbows, knees, or lower back, or if your nails have small pits or dents, psoriasis is the more likely cause. It’s an autoimmune condition where skin cells turn over too quickly, stacking up into raised plaques.
Ingrown Hairs and Acne Keloidalis
Ingrown hairs on the scalp happen when a shaved or closely cut hair curls back into the skin instead of growing outward. The body treats the trapped hair like a foreign object, producing a red, inflamed bump that can fill with pus. This is especially common along the back of the neck and the nape of the hairline.
When ingrown hairs cause repeated inflammation in the same area, the body can respond by building up thick scar tissue. This condition, called acne keloidalis nuchae, creates firm, raised bumps or a band of thickened skin at the back of the scalp. It’s most common in men with coarse or curly hair and can become permanent without treatment.
Fungal Infections
Tinea capitis, a fungal infection of the scalp, is most common in children but can affect adults too. It creates round, scaly patches that may feel raised and bumpy. In more severe cases, a painful, swollen mass called a kerion can form. A kerion looks like a large, boggy bump oozing pus, and it often gets mistaken for a bacterial infection. It’s actually an intense immune reaction to the fungus and can cause permanent hair loss in that patch if not treated.
Rarer Scarring Conditions
Folliculitis decalvans is a rare, chronic condition where the immune system overreacts to staph bacteria that are normally harmless. This triggers ongoing inflammation that gradually destroys hair follicles and leaves round or oval bald spots with scarring. Pus-filled bumps appear most often on the back of the head, and the scalp may feel tight, painful, or itchy before hair loss becomes noticeable. It tends to start during the teen years or early adulthood and affects men more often than women. The hair loss is permanent because the destroyed follicles are replaced by scar tissue.
Dissecting cellulitis is another rare scarring condition that causes deep, interconnected nodules and abscesses across the scalp. These bumps are soft, fluctuant, and can drain fluid when pressed. Like folliculitis decalvans, it leads to permanent hair loss in affected areas.
When a Bump Could Be Skin Cancer
Most scalp bumps are harmless, but the scalp is a common site for skin cancer because it gets significant sun exposure, especially along the part line and in people with thinning hair. The key warning signs are bumps that don’t heal, change over time, or look different from everything else on your skin.
Basal cell carcinoma, the most common type, often appears as a flesh-colored, pearly, or pinkish bump that may look shiny and have tiny visible blood vessels. It can easily be mistaken for a pimple or sore that just won’t go away. Squamous cell carcinoma tends to look like a rough, scaly red patch, an open sore, or a raised growth with a dip in the center that may crust or bleed. Melanoma shows up as a new, dark-colored growth or a mole that changes in size, shape, or color. Any spot larger than about 6 millimeters (roughly the size of a pea) that’s growing or evolving deserves attention.
How Scalp Bumps Are Treated
Treatment depends entirely on the cause. Mild bacterial folliculitis often clears on its own with regular washing using an antibacterial cleanser like benzoyl peroxide. If it persists, a topical antibiotic lotion or gel is usually the next step. Oral antibiotics are reserved for severe or recurring infections. Fungal folliculitis requires antifungal shampoos or, in stubborn cases, antifungal pills, since antibiotics won’t work against yeast.
For scalp acne, the simplest fix is eliminating the products causing the problem. Strip your routine back to a gentle, oil-free shampoo and see if the bumps resolve over a few weeks. A nonprescription hydrocortisone cream can help with itching in the meantime.
Seborrheic dermatitis responds well to medicated shampoos containing antifungal ingredients, while scalp psoriasis typically requires stronger prescription treatments to manage flares. Pilar cysts that aren’t bothering you can be left alone. If they grow, become painful, or get infected, a quick in-office removal takes care of them permanently.
For any bump that’s been around for more than a few weeks, is growing, bleeding, or causing hair loss in the surrounding area, a dermatologist can examine it and, if needed, take a small sample to rule out anything serious.