Bumps on the back of your head usually come down to a handful of common causes: inflamed hair follicles, cysts, swollen lymph nodes, or simply the natural bony ridge of your skull. Most are harmless, but the texture, size, and whether the bump hurts can tell you a lot about what you’re dealing with.
It Might Just Be Your Skull
Before assuming something is wrong, it helps to know that everyone has a bony bump at the base of their skull called the external occipital protuberance. It sits right where the neck meets the head, dead center. Some people have a more prominent one than others, and you might notice it for the first time while running your fingers through your hair or lying on a hard surface. If the bump is hard, immovable, painless, and centered, there’s a good chance it’s just bone. It doesn’t change in size, and pressing on it feels like pressing on any other part of your skull.
Folliculitis and Scalp Acne
If the bumps are small, red, itchy, or pus-filled, the most likely cause is folliculitis, an infection of the hair follicles. The back of the head is especially prone because of friction from hats, helmets, headrests, and shirt collars. Staphylococcus aureus (staph), a bacterium that lives on everyone’s skin, causes most cases. Fungal infections, particularly yeast, can also trigger it.
Mild folliculitis often clears on its own within a week or two if you reduce friction and keep the area clean. Stubborn or recurring cases may need a prescription antibiotic or antifungal treatment. For people who get repeated flare-ups, a body wash containing chlorhexidine and a short course of antibacterial ointment applied inside the nose (where staph colonies tend to live) can help break the cycle.
Acne Keloidalis Nuchae
This condition specifically targets the back of the scalp and neck, and it’s much more common in men with curly hair. It typically starts after adolescence as small, red, itchy bumps. Scratching turns them into pus-filled spots that look like pimples. Over time, without treatment, the inflammation thickens into raised scars and keloids, and the affected area can lose hair permanently.
The progression matters here. What begins as a few irritated bumps can become dense, scarred plaques if left alone for months or years. If you notice worsening bumps along your hairline at the nape of your neck, especially bumps that seem to be thickening or scarring, early treatment makes a real difference in preventing permanent changes to the skin.
Pilar Cysts
A pilar cyst feels like a smooth, firm, flesh-colored marble under the skin. Most people first notice one while washing or combing their hair. These cysts are filled with keratin, the same protein that makes up your fingernails, and they form around hair follicles. The scalp is their most common location by far.
Pilar cysts are usually painless and grow slowly. They can, however, get surprisingly large over time, occasionally reaching the size of a baseball in extreme cases. They become a problem if they rupture (which causes sudden pain and inflammation), if you try to pop them, or if they grow large enough to press against your skull. They also tend to run in families, so if a parent or sibling has had one, your chances are higher. Removal is a straightforward surgical procedure, but it’s typically only recommended when the cyst is bothersome or growing.
Swollen Lymph Nodes
There are small lymph nodes at the base of your skull called the occipital lymph nodes. Normally you can’t feel them at all. When they swell, they feel like soft, tender, pea-sized bumps on either side of the back of your head, close to where your neck begins. They’re usually painful or sore to the touch.
Swollen occipital lymph nodes almost always mean your body is fighting an infection or inflammation somewhere on your head or scalp. Common triggers include bacterial skin infections from cuts or scratches, scalp psoriasis (especially when a secondary infection develops), ringworm of the scalp, and even head lice, where heavy scratching opens the skin to bacteria. Less commonly, rubella and other systemic infections cause swelling in these nodes. The nodes typically shrink back to normal once the underlying issue resolves.
Seborrheic Keratoses
These are noncancerous growths that become more common with age. On the scalp, they feel raised and slightly rough, with a distinctive “stuck on” appearance, as though someone glued a waxy patch to your skin. They’re usually brown or tan but can range from nearly black to pink. Up close, the surface may look scabby, wart-like, or textured with tiny bubble-like features. They’re made of the same keratin protein found in cysts and fingernails.
Seborrheic keratoses are harmless and don’t become cancerous. Most people leave them alone unless they’re in a spot that gets irritated by combing or haircuts, in which case they can be removed easily.
How to Tell What You’re Dealing With
The texture and behavior of the bump narrows things down quickly. A hard, immovable bump right at the center base of your skull is almost certainly bone. A smooth, painless, movable lump under the skin points to a pilar cyst or lipoma (a harmless fatty lump). Small red or pus-filled spots, especially multiple ones, suggest folliculitis or acne keloidalis nuchae. Soft, tender bumps that appeared during an illness or alongside a scalp issue are likely swollen lymph nodes. A rough, waxy, raised patch that looks like it’s sitting on top of the skin fits seborrheic keratosis.
Pay attention to changes over time. Bumps that grow rapidly, bleed without trauma, feel fixed to deeper tissue, or come with unexplained weight loss or fatigue warrant a closer look. A single bump that’s been the same size for years and doesn’t bother you is far less concerning than one that appeared recently and is changing week to week.