Finding a bump on the head is very common. Some lumps or bumps occur on the skin, under the skin, or on the bone. There are a wide variety of causes of these bumps.

In addition, each human skull has a natural bump on the back of the head. This bump, called an inion, marks the bottom of the skull where it attaches to the neck muscle.

There are many reasons why you could develop a bump or lump on the back of your head. Most are harmless. In rare cases, however, a lump on the head could indicate a more serious problem.

If you notice changes with the bump on your head, if it’s bleeding or is painful, contact your doctor.

1. Head injury

If you hit your head on a hard object, you may experience a head injury. If a bump on your head appears after a head injury, it’s a sign your head was hurt, and the body is trying to heal itself.

Some scenarios that can result in head injuries are:

  • car crashes
  • sports collisions
  • falls
  • violent altercations
  • blunt force traumas

Head injuries can result in a scalp hematoma, or blood clot. If you experience a small head injury and a lump develops on your head, the developed hematoma is a sign that there’s minor bleeding under the skin. These bumps typically go away after a few days.

More traumatic head injuries can cause larger bumps or even bleeding on the brain (intracranial, epidural, and subdural hematomas).

If you experience a head injury — especially one that causes you to lose consciousness — visit your doctor to ensure you’re not bleeding internally.

2. Ingrown hair

If you shave your head, you may get ingrown hairs. This occurs when a shaved hair grows into the skin rather than through it, causing a small, red, solid bump. Sometimes, an ingrown hair can become infected and turn into a pus-filled bump.

Ingrown hairs are typically harmless and often correct themselves as the hair grows out. You can prevent ingrown hairs by letting your hair grow.

3. Folliculitis

Folliculitis is the inflammation or infection of a hair follicle. Bacterial and fungal infections can cause folliculitis. These bumps can be red or look like whitehead pimples.

This condition is also called:

In addition to bumps on the head, people with folliculitis on the scalp may also experience itching and soreness. If left untreated, the infections could turn into open sores.

Treatment for folliculitis includes:

  • daily soap washes
  • over-the-counter antibiotic creams
  • prescription pills or shampoos

In rare, extreme cases, a professional may need to perform laser hair removal or electrolysis.

There are steps you can take to avoid folliculitis, including:

  • not wearing hats
  • not shaving
  • avoiding swimming pools and hot tubs

4. Seborrheic keratosis

Seborrheic keratoses are noncancerous skin growths that look and feel like warts. They typically appear on the head and neck of older adults.

These bumps are usually harmless, even though they may look similar to skin cancer. For this reason, doctors rarely treat them. If your doctor is worried the seborrheic keratoses will become skin cancer, they may remove it using surgery.

5. Epidermoid cyst

Epidermoid cysts are small, hard lumps that grow under the skin. These slow-growing cysts frequently occur on the scalp and face. They don’t cause pain, and are skin-colored or yellow.

A buildup of keratin below the skin is often the cause of epidermoid cysts. They are very rarely cancerous. Sometimes these cysts will go away on their own. They usually aren’t treated or removed unless they become infected and painful.

6. Pilar cyst

Pilar cysts are keratin-filled sacs that form around hair follicles. Pilar cysts most frequently occur on the scalp. They can range in size, but are almost always smooth, dome-shaped, and skin-colored.

These cysts aren’t painful to touch. They aren’t typically treated or removed unless they become infected, or for cosmetic reasons.

7. Lipoma

A lipoma is a fatty, noncancerous tumor. Lipomas are the most common soft tissue tumor found in adults, but rarely occur on the head. More commonly, they occur on the neck and shoulders.

Lipomas are a collection of fat tissue located under the skin. They often feel soft or rubbery and move slightly when touched. They aren’t painful and are harmless.

There’s typically no need to treat lipomas. However, if the tumor grows, your doctor may recommend surgery to remove it.

8. Pilomatrixoma

A pilomatricoma is a hair follicle tumor that develops when follicle cells grow too much. It feels hard to the touch because it occurs after cells calcify under the skin. Pilomatricomas develop in children and adults.

These tumors commonly occur on the face, head, and neck. Typically, only one lump forms, and it grows slowly over time. These bumps normally don’t hurt.

There’s a small chance a pilomatricoma can turn into cancer. For this reason, treatment is typically avoided. If the pilomatricoma becomes infected, your doctor may remove it surgically.

9. Skin cancer

Some skin cancers can develop on skin that has frequent, intense sun exposure, like the face or a head that’s bald. Skin cancers can appear as small lumps, but also sores, patches, or spots.

Most skin cancers on the head don’t typically spread. But they should still be taken seriously. A doctor can make a proper diagnosis, which will determine the type of treatment you’ll need.

10. Exostosis

Exostosis is the growth of bone on top of existing bone. These bony growths often first appear in childhood. They can occur on any bone, but rarely occur on the head.

An X-ray can reveal if the bump on your head is an exostosis. Treatment for bony growths depends on what complications, if any, arise. In serious cases, you may require surgery.

It can be difficult to determine on your own whether a bump on your head is a cause for concern. While many bumps don’t require medical attention, some may be a sign of a serious condition.

You should talk with a doctor if the bump or lump:

  • is causing severe pain
  • changes appearance or size
  • leaks pus or discharge
  • is bleeding
  • is warm to the touch

You should also talk with a doctor if you experience:

  • headache that gets worse or doesn’t go away
  • vomiting
  • trouble with balance
  • dizziness
  • lethargy
  • memory loss
  • loss of consciousness
  • confusion
  • slurred speech
  • trouble sleeping

Most lumps on the head aren’t cancerous. But there are some skin cancers that cause lumps on your scalp or face. These include:

  • Squamous cell carcinomas (SCCs) form in the outermost layer of your skin. These can sometimes have the appearance of wart-like growths or moles. They’re usually red or pink, but may be other colors.
  • Basal cell carcinomas (BCCs) are cancerous tumors that develop in the deepest layer of your skin. They can be red or pink and look like bumps, sores, or scars. BCCs account for about 80 percent of skin cancers.
  • Nodular melanomas also form in the deepest layer of the skin. These are much less common, but much more likely to spread. They’re the deadliest form of skin cancer. These lumps are blue or black.
  • Merkel cell carcinoma (MCCs) are rare but aggressive tumors that mostly appear in people older than 70 years. They appear as a red, pink, or purple spot that can sometimes look like an insect bite. They grow quickly, getting noticeably larger in just a few weeks.

Most head and neck cancers form on the jaw or around the mouth or nose, rather than on the back of your head.

Talk with your doctor if you suspect the lump on your head could be cancerous. A dermatopathologist will evaluate the lump by:

  • examining the lump
  • asking questions about your health
  • performing a biopsy on the lump

Proper treatment for a bump on your head will depend on the cause. A doctor will make a diagnosis before recommending any treatment.

To diagnose the cause of the bump or lump on your head, a doctor might conduct any of the following:

  • physical exam
  • blood test
  • skin biopsy
  • imaging, such as a X-ray or CT scan, in some cases

Injury

For a bump on the head caused by injury, treatment may include:

  • ice
  • rest
  • ointments and bandages

You may also receive medication to help with other symptoms of the injury not related to the bump.

Infection

Infections like folliculitis tend to go away on their own eventually. In some cases, doctors may prescribe an antibiotic cream to apply to the infected areas. If infection keeps occurring, doctors may recommend hair removal.

Cysts, growths, and noncancerous tumors

Most cysts, growths, or noncancerous tumors don’t require treatment. But you may still want to have them removed. Doctors may perform any of these surgical options:

Doctors can also drain cysts, but this doesn’t actually remove the cyst. It might come back later. It’s important not to try to remove or drain a cyst yourself, as that can lead to infection.

Cancer

Diagnosis of cancer requires a skin biopsy. If the biopsy reveals that cancer cells are present, doctors will remove the cancer surgically.

Doctors usually remove skin cancers on the head or face with Mohs surgery. This type of surgery allows doctors to see where the cancer cells stop, so they don’t remove any healthy cells.

Many conditions can cause a bump or lump on the back of the head. Treatment varies based on the cause. Most bumps on the head are harmless.

If you’re unsure what’s caused the bump on your head, inform your doctor and watch the bump closely. If it changes or any of the following occur, call your doctor immediately:

  • bleeding
  • increased pain
  • growth
  • transformation into an open sore