It can be alarming to find a new bump anywhere on your body. While some lumps can be a cause for concern, a lump on the back of the neck or along your hairline usually isn’t anything serious. It could be anything from an ingrown hair to a swollen lymph node.

Keep reading to learn more about the possible causes and how to recognize them.

Sebaceous cysts are a common type of cyst that forms in blocked or damaged sebaceous glands. These glands secrete sebum, which is an oily substance that lubricates your skin and hair.

Sebaceous cysts feel like small, soft bumps. They’re usually found on your face, neck, or torso.

In most cases, your doctor can diagnose a sebaceous cyst just by looking at it. However, they may do some additional testing, such as a skin biopsy, if the bump:

  • has a diameter larger than 5 centimeters (cm)
  • shows signs of infection, such as redness, pain, or pus
  • grows back quickly after being removed

While sebaceous cysts are harmless, some people prefer to remove them for cosmetic reasons. If you want to remove a sebaceous cyst, talk to your doctor. They can remove it with a minor surgical procedure.

Ingrown hair

An ingrown hair is a strand of hair that either grows back into itself and reenters your skin or grows under your skin due to a clogged hair follicle. This results in a pimple-like bump around the hair. They’re more common in areas where you regularly remove hair by waxing, shaving, or other methods.

If have short hair, you might get ingrown hairs on the back of your neck, especially along the bottom of your hairline. You might have just one or a cluster of several.

Most ingrown hairs resolve on their own without any treatment. To avoid developing an infection, try not to squeeze or pick at an ingrown hair.

Boil

Boils (also called furuncles) are pus-filled bumps that form under the skin due to bacteria in your hair follicles. While you can have a boil anywhere, they’re common in hairy areas that are exposed to a lot of sweat and friction. This makes the back of your neck particularly vulnerable to boils.

Symptoms of a boil include:

  • a painful, pea-sized red lump
  • redness and swelling
  • an increase in size over a few days
  • a white or yellow tip that may drain pus
  • tenderness and warmth

For small boils, you can apply a warm compress to help the boil drain. Larger boils, which can grow to be the size of a golf ball, usually need to be drained by a doctor. In some cases, your doctor might also prescribe antibiotics for more severe infections.

Lipoma

A lipoma is a noncancerous, fatty lump that grows slowly, usually between your skin and muscle. You might have one or several. Lipomas are more common in middle-aged people and usually don’t cause any health problems.

While they can grow anywhere, they tend to appear on your neck, shoulders, arms, back, abdomen, or thighs. Lipomas are usually:

  • soft and doughy
  • easily movable under the skin
  • smaller than 5 cm in diameter, though they can grow bigger
  • painful if they contain blood vessels or are large enough to put pressure on a nearby nerve

Lipomas don’t require treatment unless they start to cause pain. If you think you might have a lipoma, your doctor may want to do a quick biopsy to make sure it isn’t something else. They can also help you remove a lipoma, usually either with surgery or liposuction.

Acne keloidalis nuchae

Acne keloidalis nuchae is an inflammation of the hair follicle that causes bumps on the back of the neck, along the hairline. It begins with small, itchy bumps that eventually lead to scarring and hair loss. Over time, they turn into keloids, which are large, raised bands of scarring.

The condition is more common in dark-skinned males, particularly those with thick, curly hair. Experts aren’t sure what causes it, but it may be related to:

  • close shaving
  • constant irritation from sports equipment or shirt collars
  • certain medications
  • chronic infections
  • genetic mutations

Acne keloidalis nuchae is hard to treat. Start by avoiding close shaves and making sure your shirt collar doesn’t run against the back your neck. You can also try washing the area with tar soap.

If keeping the area clean and free of friction doesn’t help, talk to your doctor. They might prescribe antibiotics or corticosteroids. In addition, laser hair removal or surgery can sometimes help.

Swollen posterior cervical lymph node

Your posterior cervical lymph nodes are located near the back of your neck. Several things can cause a swollen posterior cervical lymph node, but the most common cause is a viral infection, such as a cold or the flu.

Some other common causes of swollen lymph nodes include:

Less common causes of swollen lymph nodes include:

Depending on the underlying cause, you might also notice additional symptoms, such as:

  • pain and tenderness in the lymph node
  • runny nose, sore throat, and other symptoms of an upper respiratory infection
  • fever
  • chills
  • night sweats
  • multiple swollen lymph nodes throughout your body

If your swollen lymph nodes are due to an underlying infection, they should return to their usual size once the infection clears up. Follow up with your doctor if you can’t determine the cause or notice that the swollen node:

  • doesn’t go away after a few weeks
  • continues to grow
  • is hard and not movable
  • is accompanied by a fever, night sweats, and unexplained weight loss

Lymphoma

Lymphoma is a type of cancer that starts in the lymphocytes, which are your white blood cells. Swollen lymph nodes are often the first sign of lymphoma. However, according to the American Cancer Society, swollen lymph nodes are much more likely to be a sign of infection than of lymphoma.

Other symptoms of lymphoma include:

  • night sweats
  • fever
  • fatigue
  • skin itching
  • rash
  • unexplained weight loss
  • pain when drinking alcohol
  • bone pain

Most of the time, a lump on the back of the neck is harmless. However, it’s important to follow up with your doctor right away if you notice:

  • symptoms of severe infection, such as an ongoing fever
  • a bump that doesn’t go away after two to four weeks
  • a lump that’s hard and not moveable
  • a lump that grows or changes rapidly
  • a lump that’s accompanied by night sweats or unintended weight loss

A lump on the back of the neck is usually not serious, and most go away without any treatment. If you’re concerned or have other symptoms, talk to your doctor.

Any lump that remains longer than a couple of weeks should be examined by your doctor.