Furuncles (boils) and carbuncles (clusters of boils) are lesions that form on the skin around a hair follicle. Since these growths look similar, some people use both terms interchangeably.

Yet, furuncles and carbuncles aren’t exactly the same.

This article will explain differences between the two types of lesions, as well as explore their similarities, causes, and complications.

The main difference is that a furuncle is one boil on the skin, whereas a carbuncle is a cluster or collection of boils.

Carbuncles form when an infection travels deeper within the skin.

These lesions are similar in that they produce pus-filled lumps, and they also appear on similar parts of the body. This includes areas with hair and friction.

Some people get furuncles and carbuncles on the back of their neck, under their arms, on their thighs, or in the groin area.

Other than the number of lesions on the skin, furuncles and carbuncles have specific characteristics that set them apart.

Symptoms of furuncles

If you develop a boil, you’ll have either a bump or lump on your skin. It can be pink or reddish in color, and it’s painful or tender to the touch. Pain can be mild or moderate, depending on the size of the boil.

Furuncles typically start off small and then gradually enlarge, measuring as big as two inches. A ruptured boil releases a whitish or yellowish discharge.

Symptoms of carbuncles

Carbuncles also cause a lump on the skin that’s usually larger than a boil — measuring up to four inches. The characteristics of a carbuncle are similar to a boil, in that you may have reddish-pink, enlarged pus-filled lesions.

Since carbuncles are a deeper infection, you’ll likely experience other symptoms, too. These can include:

Here’s a look at common causes of and risk factors for boils and carbuncles.

Causes of furuncles

The most common cause of a furuncle or boil is the Staphylococcus aureus (S. aureus) bacteria.

The bacterium normally lives on the skin. But if you have an injury — such as a cut or scrape — the bacteria can penetrate your skin, triggering an infection and a boil.

Causes of carbuncles

A staph infection also causes carbuncles. In this case, though, the bacteria travel deeper within the skin, triggering a more severe infection.

Anyone can develop furuncles or carbuncles, but some people are at a higher risk. This includes those with weaker immune systems. Their bodies might be unable to fight the infection.

Being diagnosed with diabetes is another condition that makes it harder to fight infections. Also, boils and carbuncles can develop if you have eczema or a condition that weakens your skin.

Treatment for these abscesses depend on the type of lesion and the severity of the infection.

Furuncle treatment

You probably won’t need a doctor for a single boil. Furuncles typically heal on their own within a couple of weeks. You can take self-care measures to speed the healing process, though.

Apply a warm, moist compress to your skin throughout the day. This can soften the boil, helping it erupt sooner. But you shouldn’t pick or burst a boil. This might spread the infection.

You can also apply a topical antibiotic cream to your skin and take an over-the-counter pain reliever such as acetaminophen or ibuprofen to reduce pain.

Wash any cloths used for a compress in hot water to prevent spreading the infection. In addition, wash your hands after caring for your boil.

If a boil doesn’t heal on its own, make a doctor’s appointment. They may need to drain the boil in-office by making a small incision in the lesion.

Carbuncle treatment

You can use the same self-care measures for a carbuncle. But since these are deeper infections, you’ll likely need an oral antibiotic.

If you have a stubborn carbuncle that doesn’t improve, your doctor can also drain these in-office.

Severe complications can happen with these lesions, although unlikely. Here’s what to look for with both types.

Furuncle complications

Smaller boils will likely heal without problems. If you have a larger lesion, though, you may have scarring that doesn’t completely disappear.

Also, there’s the risk of bacteria spreading to other parts of your body. This can cause a secondary infection such as:

Carbuncle complications

The above complications can also occur with carbuncles.

There’s the risk of developing a blood clot behind the eye socket if a furuncle or carbuncle develops on the face. Symptoms of a clot in the face includes a severe headache and severe eye pain.

With a furuncle, you only need to see a doctor if symptoms don’t improve after 2 weeks or if a boil on the face interferes with your vision.

If you have carbuncles, you’ll likely need a prescription antibiotic for this deeper infection, so see your doctor. You should also see your doctor if you develop a fever or have recurrent skin lesions.

A furuncle and carbuncle can be painful, but they typically heal in a couple of weeks and have a low risk of secondary infections.

Even so, bring any concerns to your doctor’s attention — especially if you have a recurrent infection or increased pain, or you show signs of complications.