Cellulitis: When a Skin Infection Spreads

What is cellulitis?

Cellulitis is a common skin infection caused by bacteria. It affects the middle layer of the skin, called the dermis, and the tissue underneath.³ Staph and strep bacteria are the most common causes.³ Group A strep causes many cases, and MRSA, a type of staph that resists some antibiotics, can cause it too.¹²

It starts when bacteria get in through a crack or break in the skin.² That break can be small: a cut, a scrape, a bug bite, a new tattoo or peeling skin between the toes.¹³ Instead of one raised bump, cellulitis usually looks like a patch of redness that spreads out across the skin.

What cellulitis looks and feels like

The affected skin is usually:¹

• Red and swollen
• Painful and tender to the touch
• Warm

The skin may also look tight, glossy and stretched, or develop blisters or a dimpled, pitted surface.¹³ The red area often starts suddenly and grows quickly in the first 24 hours.³ Some people also get fever, chills, tiredness or muscle aches.¹³

Cellulitis most often affects the lower leg, usually on just one side of the body, but it can happen anywhere on the body.²

Because cellulitis can change quickly, it helps to keep track. Note when the redness started, and take a clear photo in the same light once or twice a day. That gives your doctor a simple record of whether it’s spreading or settling down.

Who is more likely to get it?

Anyone can get cellulitis.¹ Your risk is higher if you have:¹²³

• A cut, scrape, burn, recent surgery or other break in the skin
• Skin conditions such as eczema or athlete’s foot
• Long-lasting swelling in an arm or leg, called lymphedema
• Diabetes or another condition that weakens the immune system
• Poor circulation or skin ulcers
• Extra body weight
• Had cellulitis before

If you have diabetes, our guide to staph and diabetes explains why skin and foot checks matter so much.

Is it contagious, and how is it treated?

In general, you can’t catch cellulitis from another person.¹ That said, any open wound can carry bacteria, so keep it covered and wash your hands after touching it.

Cellulitis needs a doctor. Treatment is with antibiotics, either by mouth or through an IV, depending on how severe it is.¹ Your provider may draw a line around the edge of the redness with a pen, so it’s easy to see whether it spreads past that border over the next few days.³ Keeping the affected arm or leg raised can help bring down swelling and speed recovery.¹

Take the full course of any medicine exactly as prescribed, and call your provider if you aren’t improving.

Protecting your skin

Since cellulitis starts with broken skin, caring for small wounds and dry skin is the best habit you can build:²³

• Wash cuts and scrapes daily with soap and water.
• Apply a protective ointment and keep wounds covered with a clean bandage until they heal.
• Watch wounds for redness, pain or drainage.
• Moisturize regularly so skin doesn’t crack.
• Wear shoes that fit well, and take good care of your toenails.
• Treat athlete’s foot and other skin problems early.
• If you have diabetes or poor circulation, check your feet and legs every day.

Having cellulitis once raises your chance of getting it again, so these habits matter even more after an infection.² For step-by-step tips, see our guide to wound care at home.

When to see a doctor

Cellulitis can become serious if it isn’t treated. Without treatment, the infection can reach the blood and, in rare cases, spread to the heart, bones or deep layers of tissue.² Know the signs:

• Get care right away if a red area of skin spreads quickly, or you have a fever or chills.¹
• See a doctor the same day or within 24 hours if you have a red, swollen, tender rash that’s growing, even without a fever.²
• Red streaks spreading from the area, new blisters, or unusual drowsiness during treatment.³
• A fever that won’t go away while you’re taking medicine.³
• Any redness and swelling in someone who is older, has diabetes or has a weakened immune system.

Call 911 for confusion, trouble breathing, a racing heartbeat, or someone who is hard to wake. Never try to treat spreading redness at home.