How Can You Tell the Difference Between a Furuncle and an Abscess?

If you have a furuncle, it might grow to the size of a walnut. Abscesses are deeper than boils, so the physical signs might take longer to appear.

The skin is the barrier between the world around you and the organs and tissues in your body. If something damages it, harmful organisms can enter it and cause problems. Furuncles and abscesses are large bumps that can appear after bacteria have entered the body through an area of damaged skin. 

Learn what causes furuncles and abscesses, how to recognize them, and how they are treated.

Furuncles and abscesses are both infectious conditions that occur in the skin. They can both swell, develop pus, and can be contagious. It’s important to know what they are so that you can take appropriate steps to treat them and keep an infection from spreading.

What is a furuncle?

A furuncle is commonly called a boil. Boils form when bacteria infects a hair follicle. The bacteria enter the hair follicle if it is damaged and causes the infection. Skin cells begin to die, and your body sends white blood cells to fight the infection. Pus forms inside the hair follicle, and it becomes inflamed and painful.

What is an abscess?

An abscess is a bacterial infection that goes into the hypodermis—the connective tissue between the muscles and skin—and possibly deeper. Bacteria enter through a cut, wound, or even a mosquito bite and begin to infect the tissue. White blood cells are sent in by your body to fight the infection and pus forms.

Abscesses can also form around surgical sites in your body, or from deeper injuries if bacteria have moved in. They can form by an organ, or in between connective tissues.

Furuncles and abscesses have many of the same symptoms. You may not be able to tell the difference initially. If you have a boil and don’t treat it, it can spread farther down into the skin and cause an abscess.

Symptoms of a furuncle

If you have a furuncle, it might grow to the size of a walnut. You also might experience:

• Warmth around the infected area
• A red bump
• A red bump with yellowish pus in the center
• Another boil forming next to the original one

Symptoms of an abscess

Abscesses are deeper than boils, so the physical signs might take longer to appear. You may not even know you have an abscess if it is under a tooth or inside your body. If you have an abscess, you might experience:

• Redness at the infected site
• A warm feeling in the infected area
• Swelling
• Fever and chills
• Pain at the site of the infection

Furuncles and abscesses are most commonly caused by the staphylococcus (staph) bacteria. However, the bacteria are let in for different reasons. Left untreated, a furuncle can turn into a cluster of boils (known as a carbuncle) or an abscess.

Causes of a furuncle

Bacteria can get into the hair follicle if it is damaged. You can damage the hair follicle and pore by squeezing to pop a pimple, scratching a bump, or through some other external action. Once there is an opening in the pore, bacteria can enter and begin attacking the skin cells. 

Skin cells begin to die, and the body sends in white blood cells to attack the bacteria. Pus begins to form as bacteria and cells die, and the furuncle swells and becomes red and painful.

Causes of an abscess

Bacteria enter your skin through a cut, scratch, puncture, or another type of damage. Usually, the damage is deeper than the skin, which allows the bacteria to attack tissue under the skin. The process is the same and pus forms. There is usually more swelling, and the abscess becomes larger than a boil.

It might be difficult to tell the difference between an abscess and a furuncle by yourself. If you identify one or more of the symptoms on your own, it is best to see a doctor for further diagnosis.

Doctors can usually tell the difference between a boil and an abscess, but they may take some pus samples to send to the lab for testing. This can tell them which bacteria caused the infection and can help them determine the right treatment. 

Your doctor might also take some blood samples to see if the bacteria has spread. Testing helps them figure out if you have any other conditions that put you more at risk of developing infections.

If the abscess is underneath the skin or cannot be seen, the doctor will have to use imaging such as computed tomography or ultrasound to find and diagnose it.

It’s critical to seek treatment from a doctor as soon as you identify the signs or symptoms of a boil or abscess. Infections can spread quickly if left untreated. Once your doctor determines you have a furuncle or abscess, they will begin treatment by draining it. Draining may involve a small cut at the site to open it, draining the pus with sterile gauze, then disinfecting it.

If your abscess is underneath the skin or in your body, they will likely use a technique called percutaneous abscess drainage. Doctors insert a needle through the skin to the abscess and use a catheter to drain the pus. Draining can take up to a few days to complete.

Once drainage is complete for both types of infection, doctors prescribe an antibiotic regimen to treat any further bacterial infection or bacteria that are left.