Anna Giorgi is a health and lifestyle writer who specializes in providing straightforward and accurate healthcare communications for consumers.

Susan Bard, MD, is a board-certified dermatologist in New York City.

A cyst and a boil can both look like a bump, though their causes differ. For example:

This article describes how a boil and a cyst differ in their symptoms, causes, and treatment.

While both types of bumps can appear anywhere on your body, symptoms of a boil can vary from symptoms of a cyst.

Knowing how each type of skin bump looks, feels, and affects your skin provides valuable clues when trying to identify a new bump on your skin.

A boil appears as a red to purple swollen skin lump, similar to a pimple. It usually has one or more whiteheads, called pustules, that form in the center. Pustules contain a white-yellow, pus-like fluid that may ooze from the boil. If several adjacent follicles become infected from the spread of the bacteria, they may form a larger nodule called a carbuncle.

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The size of a boil varies. It can range from the size of a cherry stone to the size of a walnut, and some grow even larger. The size of a boil may increase quickly as the pus increases within the boil. As the amount of pus increases, pain may become more intense.

A boil may feel tender to the touch or hurt constantly. You may notice itching at the site of the boil before it forms. Depending on the extent of the infection, you may also develop a fever and/or fatigue.

A boil usually appears in one of the following areas:

A cyst is a closed, saclike tissue pocket that forms under the skin. It usually contains keratin. There are hundreds of types of cysts. Epidermoid cysts are the most common cysts that develop under the skin.

These cysts appear as smooth lumps that are whitish-yellow or the color of your skin. They can range in size from one-half inch to several inches across. A cyst is usually painless and may not require treatment.

Reproduced with permission from © DermNet New Zealand www.dermnetnz.org 2023.

A cyst is usually benign (noncanerous). It is painless and doesn't cause other symptoms unless it affects the normal function of the body system. Skin cysts usually appear in one of the following areas:

Swollen, fast-growing red skin bump

Filled with whitest-yellow colored pus

Painful to the touch and/or constantly sore

White or yellow head filled with pus

Possible fatigue and/or fever

Filled with a yellow, foul-smelling keratin

Swollen, warm to the touch, painless

White or yellow color with a blackhead

No related fever or fatigue

The causes of a boil and a cyst differ. A boil is caused by an infection, while a cyst is not.

A boil develops from an infection of a hair follicle and the surrounding tissue. The most common source of infection is a staph infection caused by the Staphylococcus aureus (S. aureus) bacterium. The infection causes the skin tissue inside the boil to die. Then, a pus-filled hollow space, called an abscess, develops within or just below the skin's surface.

Most people have S. aureus bacteria on their skin and in areas like the lining of their noses without boils recurring. Boils are more likely to develop in people with the following characteristics:

A boil is contagious when a break in the skin and person-to-person contact with pus drainage and skin bacteria occurs. It may also spread from contact with contaminated surfaces and objects.

The skin cells in the outermost layer of your skin, called the epidermis, slowly shed as newer cells move to the surface of your skin. Cysts are formed when the surface skin is folded in on itself. Dead skin then fills the cyst, and it can't be shed the way it is elsewhere on the body. When a cyst reaches a certain size, it usually stops growing.

A pimple occurs when dead skin cells, excess oil, and bacteria get trapped inside a pore. As the bacteria multiply, they cause inflammation, and a pimple forms on the skin's surface.

A pimple is typically painless and smaller than either a boil or a cyst. It usually grows no larger than the size of a dime and does not increase much in size after it erupts.

While a pimple often occurs in clusters, a cyst or boil usually appears as a single lump. Unlike a cyst or boil, a pimple may be a sign of acne, a chronic condition that recurs despite treatment of one pimple.

Only a healthcare provider can make an accurate diagnosis of your skin bump. Your healthcare provider may be able to recognize a boil or cyst based on the appearance of the bump and a description of your symptoms.

Factors such as when you first noticed the bump, how quickly it grew, whether it has changed in size, and if it is painful can help make a diagnosis.

Depending on the symptoms of your skin bump, your healthcare provider may perform the following laboratory tests. These tests may be performed if you often get boils, have several boils at the same time, or have a high risk of complications from a boil or cyst:

A boil or cyst can heal on its own without treatment. However, if your lump is causing pain, fever, inflammation, and/or interference with other body systems, such as vision or mobility, it can make a wait-and-see approach intolerable. Your healthcare provider can determine whether treatment can help promote healing, relieve pain, and reduce your risk of complications.

If you have a boil or cyst, you may be able to treat it at home with the following techniques:

The American Academy of Dermatology (AAD) warns that you should never squeeze or pierce a boil or cyst yourself. Doing this risks the possibility of spreading an infection from a boil. If the abscess bursts inside your body, there is a risk of blood poisoning (septicemia). If you squeeze, puncture, or lance a cyst, you can risk infecting it, and the cyst may become a boil.

A dermatologist may have to surgically drain a deep or large boil or cyst due to infection, inflammation, or aesthetics. Treatment of a boil involves lancing the abscess, draining the pus, and removing the infected material.

A problematic cyst can be treated with simple excision (surgical removal) of the cyst and cyst wall. This prevents the cyst from recurring. The procedure can also be performed with a minimally invasive technique that removes the cyst through a small hole.

Consult your healthcare provider if you have a boil or cyst with the following symptoms:

If your boil is severe or it comes back after healing, your healthcare provider may prescribe antibiotics to kill the bacteria.

You may be able to prevent boils by taking the following precautions:

There is no known technique for preventing skin cysts. However, you can prevent potential infection and scarring of a cyst if you avoid squeezing, popping, lancing, or trying to drain the cyst yourself. Doing this increases the risk of inflammation or infection.

Boils and cysts are two common types of skin bumps. They can look alike even though their causes differ.

A boil is caused by a bacterial infection that affects a hair follicle and the tissue around it. A cyst occurs when skin cells grow and then can't reach the surface and become blocked below the skin.

While both skin lumps may heal without treatment, home care or surgery to remove the boil or cyst may be needed. Treatment for a boil can involve using antibiotics to treat the infection. A cyst usually doesn't need treatment unless it causes pain or prevents you from doing normal tasks.

Proper handwashing is one way to reduce the risk of boils and the spread of infection that occurs with them. There is no known way to prevent a cyst. Removing the cyst prevents it from recurring.

Institute for Quality and Efficiency in Health Care (IQWiG). Boils and carbuncles: overview.

Cedars-Sinai. Epidermoid cysts of the skin.

Ibler KS, Kromann CB. Recurrent furunculosis - challenges and management: a review. Clin Cosmet Investig Dermatol. 2014;7:59-64. doi:10.2147/CCID.S35302

Harvard Health Publishing. Cysts (overview).

American Academy of Pediatrics. Boils, abscess and cellulitis.

American Academy of Dermatology Association. Acne: signs and symptoms.

Kaiser Permanente. Skin cyst: home treatment.

American Academy of Dermatology Association. How to treat boils and styes.

Song SW, Burm JS, Yang WY, Kang SY. Minimally invasive excision of epidermal cysts through a small hole made by a co2 laser. Arch Plast Surg. 2014;41(1):85-88. doi:10.5999/aps.2014.41.1.85

By Anna Giorgi Anna Zernone Giorgi is a writer who specializes in health and lifestyle topics. Her experience includes over 25 years of writing on health and wellness-related subjects for consumers and medical professionals, in addition to holding positions in healthcare communications.

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