Boils and cysts can both look like bumps on your skin. The main difference between a cyst and a boil is that a boil is a bacterial or fungal infection. Cysts aren’t contagious, but boils can spread bacteria or fungi on contact.
A cyst is a smooth, round, closed sac under your skin filled with fluid or semisolid material. Most cysts are slow-growing and benign (noncancerous). Cysts may be problematic, depending on their size and location on your body. There are hundreds of types of cysts.
The most common skin cysts are:
- epidermoid, also called inclusion cysts (used to be called sebaceous cysts)
- pilar, also called trichilemmal cysts
A boil (furuncle) is a painful skin bump filled with pus. It’s usually caused by the staph bacteria that are naturally present on your skin. These bacteria can lead to an infection or inflammation within a hair follicle or oil gland.
Boils can appear anywhere on your body. A boil is also called:
Cysts can appear under the skin anywhere on your body, except your palms and soles. Cysts range in size from a few millimeters (1 mm = 0.039 inch) to several centimeters (1 cm = 0.39 inch). Symptoms vary, depending on the type of cyst.
In general, cysts are:
- not painful, unless they burst under the skin or become inflamed
- smooth when touched
|Epidermoid cysts||Milia cysts||Pilar cysts|
|commonly found on back, face, or chest||usually found on the face||commonly found on the scalp|
|can be moved around under the skin||very small (1-2 mm)||often dome-shaped|
|may have a small dark plug (blackhead) at center||hard||firm and smooth|
|may ooze a foul-smelling cheeselike substance||white||flesh-colored|
|twice as common in men than women||similar to epidermoid cysts|
Boils are usually small, but can be as large as a baseball. They begin as red pimples that are red in appearance.
- development of a white or yellow center
- oozing pus or crusting
- fatigue or fever
- general feeling of malaise
The cause of many cysts is unknown.
In general, a cyst forms when cells from the top skin layer (epidermal cells) multiply under the skin. Cysts can also develop in the following ways:
- Some cysts may form after an injury to the site.
- Sometimes a blocked gland or swollen hair follicle may result in a cyst.
- Milia may form because of steroid cream use or due to some cosmetics.
- Some infants are born with milia, which disappear in time.
- Pilar cysts may be hereditary.
Staph bacteria (Staphylococcus aureus) are the cause of most boils. These bacteria normally live on your skin or in your nose.
When your skin is scraped or broken, the bacteria can enter via a hair follicle and cause an infection. The boil that forms is the result of your body’s immune system trying to get rid of the bacteria.
The hair follicle can be located anywhere on your body. Boils most often are found in skin areas where there’s friction, such as the:
A fungal infection may cause some boils.
Risk factors for cysts and boils are different. You can’t contract a cyst, but you can contract an infection that leads to a boil.
Boils result from a bacterial or fungal infection. Risks include the following:
- If you have a skin condition like acne, psoriasis, or eczema, you’re more likely to have breaks in your skin, which could lead to a boil.
- If you’re in close contact with someone who has a boil, you may contract the bacteria that caused the boil.
- If you have a compromised immune system, you have an increased risk of developing a boil.
- If you have diabetes, your risk is increased because it’s harder to fight off an infection.
- If you’re overweight, your risk may be increased.
Treatment for cysts and boils is different. This is because an infection causes a boil. But sometimes a benign cyst may become infected.
Sometimes an epidermal cyst may become inflamed and swollen. The American Academy of Dermatology (AAD) advises that antibiotics shouldn’t be prescribed unless it’s confirmed the cyst is infected.
For an inflamed cyst, the AAD advises drainage of the cyst or an injection of a corticosteroid.
Some cysts may be troublesome or unsightly to some people because of their location. In these cases, treatment may involve surgical removal. A minimal incision method is recommended to prevent scarring.
A 2005 study involving 82 people who had cysts removed reported no complications and no recurrences of the cysts.
If you have no systemic symptoms of infection, you can take care of a boil at home. To treat a boil at home, do the following:
- Apply a warm, moist compress three to four times per day for 10 to 15 minutes each time to help the boil drain.
- Keep the area clean. Wash your hands after treating the boil.
- Keep a clean bandage over the boil.
- Avoid picking at the boil or trying to squeeze it.
Some symptoms indicate a doctor’s help is needed. See your doctor if:
- your boil gets worse
- you have more than one boil
- your boil doesn’t heal in a couple of weeks
Your doctor may drain the boil or may prescribe an antibiotic to help healing.
If you have a noncancerous cyst, your outlook is very good. If you choose to remove a cyst, surgery is usually successful.
Most boils heal on their own within one to three weeks. Some boils may require treatment by a dermatologist.
You can’t do anything to prevent a cyst from forming. But you can prevent a cyst from becoming infected by not picking at it or trying to pop it on your own.
Good hygiene is the best way to prevent boils. If you have a boil, wash your hands thoroughly and often. This helps keep the bacteria or fungi from spreading to other areas of your body or to other people.
Take care if someone you work with or live with currently has a boil.
Wash any towels, toys, or clothing that may have come in contact with the boil. To kill any bacteria or fungi that may be present on these items, use hot water and soap. Dry the items in a dryer using the hot setting.