You may be accustomed to pimples showing up on your face, but seeing one in your armpit can be surprising. Some bumps in your armpit area may be painless, while others — such as boils — can hurt, especially if you move your arm the wrong way. If you’re wondering what may cause armpit bumps, you’re not alone.

In some cases, these underarm lumps may be harmless, stemming from ingrown hairs, clogged pores, or other reasons. But they may also be caused by chronic conditions, such as hidradenitis suppurativa (HS). Read on to discover what these pimples and boils may mean and how you can treat them.

What’s the Difference Between a Pimple and a Boil?

Pimples from acne may form on your skin when sebaceous glands (called oil glands) become inflamed or clogged. These glands are located across your body. Even though pimples often show up on the face and scalp, they may also appear on your back, stomach, chest, and other locations. In fact, humans have sebaceous glands everywhere except the soles of the feet and palms of the hands.

If these glands get irritated, an acne-related pimple can form. This can happen when:

• You get more bacteria on your skin than usual.
• A protein called keratin develops abnormally near the glands.
• The sebaceous glands produce too much oil.

Another type of lump that may form in your underarm area is a boil. Differentiating pimples from boils can be challenging at first. The main difference is that boils (also called furuncles) are usually caused by bacterial infections. They’re bigger than pimples and tend to hurt more. Pimples may develop a white head, but boils almost always do. Boils may also be warm when you touch them.

Not every raised bump in your armpit is a pimple. Always reach out to a healthcare provider to assess any new bumps or lumps in your armpit.

What Causes an Armpit Pimple or Boil?

Below are some potential causes for lumps under your arms.

Skin Infections

Sometimes, bacterial skin infections may cause pimples that resemble acne. For instance, a type of bacteria called Staphylococcus aureus (staph) lives on your skin most of the time. If this bacteria enters your body through an opening (such as an area where you popped a pimple), staph can get into your bloodstream, which is dangerous. Staph infections are typically the cause of boils.

If you notice a bump in your underarm area that won’t go away or that hurts, it could be due to an infection.

Folliculitis

Folliculitis is an inflamed hair follicle. It can occur on any part of your body that grows hair, including your underarms. The bumps that folliculitis causes look a lot like pimples. They may be itchy or painful.

Folliculitis may result when something irritates your hair follicle, such as shaving or sweating a lot. People also get folliculitis from hot tubs that aren’t cleaned well enough. More than one bump may appear with folliculitis, depending on the cause. For instance, if you get this condition due to shaving, you may see several pimples in a row where each hair follicle is located.

Ingrown Hairs

An ingrown hair can develop in your armpit after removing hair by shaving, waxing, or using other methods. When the hair starts to grow back, it may curl and grow beneath the skin instead of breaking through the surface. This can lead to a bump that looks like a pimple. The area may become discolored, itchy, or uncomfortable.

Prickly Heat

If sweat gets trapped under your skin and clogs your sweat glands, it can lead to a rash known as prickly heat (also called heat rash or miliaria). This condition causes itchy red bumps on lighter skin, and gray or white bumps on darker skin. It’s most likely to appear in areas where skin rubs against skin, such as the armpits, under the breasts, or between the thighs. Prickly heat may look like clusters of small pimples, but it's usually part of a larger rash that feels irritated or itchy.

Hidradenitis Suppurativa

HS is a skin condition caused by hair follicle blockages. This condition typically develops in parts of the body where the skin folds rub together, such as the underarms or the groin. When HS lesions develop, they may look just like a pimple. In other cases, the underarm bump will form into a boil, which is deeper under the skin and more painful. These bumps may rupture and drain fluid.

Hidradenitis Suppurativa vs. Other Armpit Pimples and Boils

You may have trouble determining what caused your armpit pimples and boils. HS lesions typically heal more slowly than acne pimples and tend to come back. They often start out deeper under the skin and then break open, releasing a fluid that may have an unpleasant smell. If the condition is severe, the boils may be so painful that they make it difficult for you to move.

Only a dermatology expert or other healthcare professional can definitively determine what’s causing your armpit pimples or boils. Always get medical attention if you see any new or worsening skin bumps anywhere on your skin, including your underarms.

How To Get Rid of Armpit Pimples

Depending on the cause of your armpit pimples, some home remedies may help ease your symptoms. Try to avoid touching your pimple, and don’t pick at it. Make sure anything that comes into contact with the pimple is clean so you avoid introducing bacteria. Try not to shave around it so it heals well, and wear loose-fitting clothes that won’t constrict your armpit.

If your dermatologist diagnoses you with hidradenitis suppurativa, they’ll review your treatment options with you. Several options are available for treating HS lesions under the arms.

Home treatment may help in some situations, but some conditions, such as a bacterial infection, require medical treatment. Reach out to a doctor or go to an urgent care center if the bump in your underarm area:

• Feels painful or hard
• Lasts two weeks or longer without resolving
• Comes back after going away
• Grows larger
• Occurs alongside signs of infection, such as a fever

A doctor can help provide treatment for the underlying cause of pimples in the underarm area. They’ll also help you find ways to manage pain or infection that comes along with it and let you know whether any new skin care routines may help you prevent further issues.

Talk With Others Who Understand

On myHSteam, people share their experiences with hidradenitis suppurativa, get advice, and find support from others who understand.

Have you experienced any pimples or boils in your armpit? Let others know in the comments below.