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What Is Cellulitis?

Cellulitis (pronounced: sel-yuh-LY-tis) is a skin infection that involves areas of tissue below the surface of the skin.

Cellulitis can affect any area of the body, but it's most common on exposed body parts, such as the face, arms, or lower legs.

What Causes Cellulitis?

Many different types of bacteria can cause cellulitis. The most common ones are group A streptococcus and Staphylococcus aureus. These bacteria usually live harmlessly on the skin and in the nose and throat, but sometimes they can get into the body through an area of broken skin, like a cut, bite, scratch, or body piercing, leading to infection. 

Cellulitis can also sometimes happen when there isn’t any obvious broken skin, especially in people who have chronic conditions or who take medicines that affect the immune system.

Cellulitis is not contagious. It can't spread from person to person. But the bacteria that cause it can spread from an open wound to other people.

What Are the Signs & Symptoms of Cellulitis?

Cellulitis begins with a small area of skin that's:

  • painful
  • swollen
  • warm
  • red

As this area begins to spread, a person may begin to feel ill and get a fever. Swollen lymph nodes (sometimes called swollen “glands”) are sometimes found near the area of infected skin.

The time it takes for symptoms to start varies, depending on which bacteria cause the cellulitis. For example, with cellulitis caused by Pasteurella multocida, often found in animal bites, a person can have symptoms less than 24 hours after the bite. But cellulitis caused by other types of bacteria may not cause symptoms for several days.

How Is Cellulitis Diagnosed?

A doctor can usually diagnose cellulitis by asking questions and examining the area of affected skin. Usually other tests aren’t needed unless a person looks very sick. Then the doctor may take a blood sample to see if bacteria are in the bloodstream.

How Is Cellulitis Treated?

For a mild case of cellulitis, doctors prescribe antibiotics by mouth. You should start to feel better in a couple of days, but be sure to take all the antibiotics as prescribed. Otherwise, the infection can return. To see if the treatment is working, you can draw a line around the red area of infected skin and watch to see if the edges of the red area change.

People with a more serious infection, or one that doesn’t get better after they take antibiotics by mouth, might need to get intravenous (IV) antibiotics in a hospital.

Can Cellulitis Be Prevented?

To prevent cellulitis, protect skin from cuts, bruises, and scrapes. This isn't easy, especially if someone is active or likes to play sports.

To protect yourself:

  • Use elbow and knee pads while skating.
  • Wear a bike helmet when riding.
  • Wear shin guards during soccer.
  • Wear long pants and long-sleeved shirts while hiking in the woods (this can also protect you from bug bites and stings).
  • Wear sandals on the beach.

If you do get a cut or scrape, wash it well with soap and water. Apply an antibiotic ointment and cover the wound with an adhesive bandage or gauze. Check wounds often for the first few days to see if any signs of cellulitis begin.

When Should I Call My Doctor?

Call your doctor whenever any area of your skin becomes red, warm, and painful — with or without a fever. This is especially important if the area of skin is on the hands, feet, or face (particularly ear, nose, or eyebrow piercings) or if you have an illness or condition that weakens the immune system.

Check with your doctor if you get a large cut or a deep puncture wound. Cellulitis can happen quickly after an animal bite. So call your doctor if an animal bites you, especially if the puncture wound is deep. Not too many people get bitten by other people, of course, but human bites can cause skin infections too.

What Can I Do to Feel Better?

Take the antibiotics prescribed by the doctor exactly as directed and for the full course. Follow your doctor's suggestions for treating the area of cellulitis, such as raising the affected part of your body or applying heat or warm soaks to it. You can also take over-the-counter pain relievers such as acetaminophen or ibuprofen to ease pain and keep a fever down.

After you've taken antibiotics for 1 or 2 days, your doctor may schedule an office visit to check that the area of cellulitis has improved. This means that the antibiotics are working against the infection.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date Reviewed: Mar 20, 2023

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