Cellulitis is a bacterial infection that affects the deep layers of the skin. It occurs when a break in the skin allows bacteria below the skin’s surface. Symptoms can include:

The bacteria most commonly associated with cellulitis are streptococcus and staphylococcus, but there are a growing number of cases with a serious staphylococcus infection called methicillin-resistant Staphylococcus aureus (MRSA).

If left untreated, cellulitis can rapidly spread throughout your body — including your bloodstream and lymph nodes — and become life-threatening. If caught early, your doctor can treat it with oral antibiotics and basic wound care.

Cellulitis is not usually spread from person to person. Typically, you cannot get it from someone who has it or spread it to another person. That being said, if you have an open wound that directly comes into contact with the infected area of a person with cellulitis, there’s an increased chance you could get a case yourself. Risk factors that can increase your chances include:

  • Injury. A break in the skin can serve as an entry point for bacteria.
  • Skin condition. Skin conditions such as athlete’s foot and eczema can give bacteria an entry point.
  • Weak immune system. You’ll be more susceptible to infections if you have a condition — such as HIV/AIDS, leukemia, or diabetes — that weakens your immune system.
  • Obesity. You have a higher risk of developing cellulitis if you’re overweight or obese.
  • History. If you’ve had cellulitis in the past, you’ll be prone to developing it again.

Cellulitis can affect your eyes as well as your skin. The two types of cellulitis of the eyes are:

  • Periorbital (or preseptal) cellulitis. This condition affects the tissue of the eyelid and is most common in young children.
  • Orbital cellulitis. The more serious of the two, this condition affects the eye socket, causing swelling that inhibits the eye from properly moving.

Cellulitis of the eye is typically treated with an oral antibiotic. If the oral antibiotic is not effective, your doctor might suggest intravenous antibiotics and, in some cases, surgically drain fluid from the injured area.

Under most circumstances, cellulitis is not contagious. Generally, cellulitis is a common skin condition that usually responds to simple treatment. It can be dangerous, however, particularly if left untreated.

If you have a tender, red, warm, and swollen rash that’s expanding, see your doctor as soon as you can. If that rash is changing rapidly and you have a fever, see your doctor right away or seek emergency care.