Cysts and boils, while similar, differ in cause and appearance. A boil is red or discolored, swollen, and contains pus, like a pimple. A cyst is under the skin and is usually painless but can resemble a boil if it ruptures or becomes infected.

Cysts and boils may be easily confused with each other. However, they differ in various ways, including cause and overall appearance. Boils are generally due to an infection. Cysts do not always have a known cause but may be due to rapid multiplication of skin cells.

This article provides an overview of cysts and boils, including their causes, symptoms, and treatment. It also explains how a person can tell the difference between the two.

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It can be easy to confuse cysts and boils as they may have similar symptoms.


A cyst is a small fluid-filled lump that can form in or on a person’s body. They are typically benign or noncancerous.

According to the American Osteopathic College of Dermatology (AOCD), there are three common types of skin cysts:

  • Epidermal (sebaceous) cysts: This is the most common type of benign skin tumor. It is made of the most superficial parts of the skin. These tend to be easily moveable nodules. Common locations include neck, back, ears, scalp, and face. They are the result of clogged hair follicles or penetrating injuries.
  • Trichilemmal (pilar) cysts: These may appear similar to epidermal cysts. However, trichilemmal cysts typically occur on the scalp, and there are multiple cysts. The wall of the cyst is generally thicker than epidermal cysts.
  • Milia: These are firm, small, and whitish lesions that typically appear on the face. They commonly occur around the eyes. Generally, milia appear for no reason. However, some conditions or dermatological treatments can trigger their appearance. They are common in newborns and infants.

Other types of cysts include:


Boils or furuncles are pus-filled lumps under the skin that form around hair follicles. They are typically the result of bacterial infections.

Boils may appear similar to pimples, with yellow tops or heads. However, boils occur deeper in the skin than pimples, and they tend to be more painful.

Sometimes, boils can develop in a cluster. This is known as a carbuncle. This occurs due to a more sever infection and can cause other symptoms, such as fever.

Skin cysts and boils can present in a similar way. However, there are ways to tell them apart. If a person experiences a new or unexplained lump on or under their skin, they should speak with a healthcare professional.


Cysts can form on most areas of the body, including:

  • neck
  • head
  • chest
  • face
  • back

They can also appear on the scrotum or inside the vagina.

The characteristics of a cyst include:

  • often filled with pus or fluid
  • round lumps just under the skin
  • slow growing
  • varying in size, typically ranging from smaller than a pea to several centimeters
  • may become red or discolored and sore if they become infected


Boils most commonly occur on the face and neck, including the back of the neck. However, they can also develop on other areas of the body, including:

  • groin
  • armpits
  • back
  • bottom
  • thighs

Boils are hard and painful lumps. They are typically filled with pus. Boils may:

  • begin as an itchy, tender spot
  • leak pus
  • range in size from a cherry stone to a walnut

Despite their similar appearance, there are important differences between cysts and boils.


If a person has a cyst without inflammation, they may not experience any associated symptoms. However, if the cyst does become inflamed, it may be red or discolored, swollen, and painful.

A cyst can rupture on sudden exposure to pressure, for example, if a person falls on it. If it does burst, a person may notice yellow, unpleasant-smelling pus.


It is not clear exactly why people get cysts, but they form when skin cells quickly multiply.

Gardner’s syndrome and Gorlin’s syndrome can cause a person to develop cysts. These lumps may also have an association with sun damage to a person’s skin, and some medications might increase the likelihood of a cyst forming.

Cysts can also appear after a person sustains damage to their skin, although the underlying cause is often not clear.


Cysts often do not require any treatment, especially if a person is not experiencing any other symptoms. They may go away on their own.

It is important not to squeeze or puncture a cyst. If it bursts, it may become infected, or if an infection has already developed, it may spread.

If treatment for a cyst is required, it usually involves minor surgery to remove it. A doctor will give the individual a local anesthetic before removing the whole of the cyst, making as small an incision as possible to try to prevent scarring.


Unlike most cysts, boils are typically swollen, red or discolored, and sore. People may see yellow pus in or on the boil.

A boil may make a person feel weak or tired if they develop a fever because of the bacterial infection.


Boils usually occur as a result of bacterial infection around a hair follicle. This infection causes the surrounding skin cells to die, and pus then replaces them. Sometimes, several boils will develop in a cluster (carbuncle).

If a person has other skin conditions, such as eczema or psoriasis, they may be more likely to develop a boil because their skin is more susceptible to bacterial infection.


Although bacteria are the underlying cause of boils, antibiotics are not usually the first treatment for a boil unless it is severe or many boils have formed.

People can often manage boils at home. The American Academy of Dermatology (AAD) recommends applying a warm, damp, clean cloth to the boil. Doing this encourages the boil to release its pus, which helps it heal. Ibuprofen can help relieve pain and inflammation.

A person should not squeeze a boil as this may worsen the infection.

If a boil is severe or persistent, a healthcare professional might take a sample of the pus in the boil and send it to a laboratory to determine which bacterial infection has caused it. When they know which bacteria are responsible, they can prescribe the most effective antibiotic to clear the infection.

Although cysts and boils may look similar, especially if a cyst becomes inflamed, there are important differences between them.

Cysts are not generally painful, but most boils are sore. Boils tend to be a little larger than cysts and appear red or discolored and swollen.

Cysts and boils may not require medical treatment. However, if they persist, become more painful, or affect movement in the area, a person should speak with a healthcare professional.