It can be difficult to determine if the irritated bump on your skin is acne or a boil. Both are caused by bacteria in the pores and hair follicles. They differ in how they are treated and factors that put them at higher risk.

All kinds of bumps and lumps can pop up on your skin. Sometimes when you notice a growth, it’s not immediately obvious what you have. A red or white-topped bump could be a pimple, but it might also be a boil. The two types of growths can look similar.

Keep reading to learn how to spot the difference between pimples and boils, and how to treat whichever one you have.

Acne is one of the most common skin conditions. At any given time, up to 50 million Americans will have some form of acne.

Acne comes in different sizes, shapes, and types. It often forms on the face, but you can also get breakouts on your neck, back, shoulders, and chest. There are a few kinds of acne and each looks different:

  • Blackheads form at the skin’s surface and are open at the top. Visible dirt and dead skin cells inside the pore make it appear black.
  • Whiteheadsform deeper in the skin. They’re closed at the top and filled with pus, which makes them look white. Pus is a thick mixture of white blood cells and bacteria.
  • Papulesare larger, hard pink or red bumps that can feel sore when you touch them.
  • Pustules are red, inflamed bumps that are filled with pus.
  • Nodules are hard lumps that form deep inside the skin.
  • Cysts are large, soft, and filled with pus.

As pimples fade, they can leave dark spots on the skin. Sometimes acne can cause permanent scars, especially if you pop or pick at your skin.

A boil is a red bump that is swollen and red around the outside. It slowly fills with pus and gets larger. You’re most likely to see boils in areas where you sweat or where your clothes rub against your skin, like your face, neck, underarms, buttocks, and thighs.

Several boils can cluster together and form a growth called a carbuncle. A carbuncle is painful, and it can leave a permanent scar. Carbuncles sometimes cause flu-like symptoms, such as fatigue, fever, and chills.

Acne starts in pores. Pores are tiny holes in your skin that are the openings to hair follicles. These holes can fill with dead skin cells, which form a plug that traps oil, bacteria, and dirt inside. Bacteria make the pore swell up and turn red. Pus, a thick, white substance made up of bacteria and white blood cells, sometimes fills the pimple.

Boils also start in hair follicles. They’re caused by bacteria like Staphylococcus aureus, which usually live harmlessly on the surface of your skin. Sometimes these bacteria can get inside the hair follicle and cause an infection. An open cut or injury gives bacteria an easier access route inside.

You may associate pimples with the teenage years, but you can get them at any age. An increasing number of adults today have been diagnosed with acne.

You’re more likely to get acne if you have hormone changes, such as during puberty and pregnancy, or when you start or stop taking birth control pills. And an increase in male hormones in both males and females causes the skin to produce more oil.

Some other causes of acne include:

  • taking certain medicines, such as steroids, anti-seizure drugs, or lithium
  • eating certain foods, including dairy and high-carb foods
  • using cosmetic products that clog pores, which are considered comedogenic
  • being under stress
  • having parents who had acne, which tends to run in families

Anyone can get a boil, but boils are most common among teens and young adults, especially males. Other risk factors include:

  • having diabetes, which makes you more vulnerable to infections
  • sharing towels, razors, or other personal hygiene items with someone who has a boil
  • having eczema
  • having a weakened immune system

People who get acne are also more likely to get boils.

Dermatologists treat skin conditions like acne and boils. See a dermatologist for your acne if:

  • you have a lot of pimples
  • over-the-counter treatments aren’t working
  • you’re unhappy with the way you look, or the pimples are affecting your self-esteem

Small boils are pretty easy to treat on your own. But see a doctor if a boil:

  • is on your face or spine
  • is very painful
  • is bigger than 2 inches across
  • causes a fever
  • doesn’t heal within a couple of weeks, or keeps coming back

You can often treat pimples yourself with over-the-counter creams or washes you buy at a drugstore. Usually acne products contain ingredients like salicylic acid and benzoyl peroxide, which stop your pores from getting clogged and kill bacteria on your skin.

For more severe acne, your doctor can prescribe stronger medicines, such as:

  • antibiotics to kill bacteria
  • birth control pills to adjust your hormone levels if you are female
  • isotretinoin (Absorica, Zenatane), a form of vitamin A

If acne doesn’t improve with one of these treatments, your doctor might try:

  • lasers or light therapy to reduce the amount of bacteria in your skin
  • chemical peels
  • drainage and extraction, in which your doctor injects medicine into a cyst and then drains it

You can treat small boils yourself by repeatedly applying a warm, wet washcloth. Eventually, the pus should drain out and cause the boil to shrink.

For larger boils, your doctor can cut a small hole and drain out the pus. You might also need to take antibiotics to treat the infection.

Do not try cutting a hole in a boil yourself. This can lead to infection and scarring.

Mild acne will often clear up on its own or with a little help from an over-the-counter treatment. Severe acne can be more difficult to treat.

When you have acne, it doesn’t just affect your skin. Widespread or constant breakouts can impact your self-esteem, and cause anxiety and depression.

Within a few days or weeks, most boils will pop. The pus inside will drain out and the lump will slowly disappear. Sometimes large boils can leave a scar. Very rarely, an infection can spread deep into the skin and cause blood poisoning.

To prevent acne breakouts:

Wash your face at least twice a day with a mild cleanser. Keeping your skin clean will prevent oil and bacteria from building up inside your pores. Be careful not to over-wash your skin, which can cause your skin to dry out and produce more oil to compensate.

Choose oil-free or noncomedogenic skin care products and makeup. These products won’t clog your pores.

Wash your hair often. Oil that builds up in your scalp can contribute to breakouts.

Limit your use of helmets, headbands, and other accessories that press against your skin for a long period of time. These products can irritate your skin and cause pimples.

To prevent boils:

  • Never share personal hygiene items like razors, towels, and clothes. Unlike pimples, boils are contagious. You can catch them from someone who’s infected.
  • Wash your hands with warm water and soap throughout the day to avoid transferring bacteria to your skin.
  • Clean and cover open sores to prevent bacteria from getting inside and causing an infection.
  • Never pick or pop a boil you already have. You could spread the bacteria.