Cellulitis Information - Bacterial Skin Infection

Bacterial Skin Infection

Cellulitis of leg
Cellulitis of the leg. DEA Picture Library

Cellulitis is a bacterial infection of the deeper layers of the skin, the dermis, and the subcutaneous tissue. In adults and children, cellulitis is most often caused by Streptococcus and Staphylococcus Aureus bacteria. Sometimes Haemophilus influenzae type B can cause cellulitis in children younger than 3, but this has become less common since we've been vaccinating against this bacteria. Knowing the type of bacteria that commonly cause cellulitis helps doctors determine the best antibiotic to treat the infection.

How Someone Gets Cellulitis

Bacteria are able to cause an infection if they can get into the skin through a break in the skin barrier. This can happen with cuts, scrapes, ulcers, and surgical wounds. Unfortunately, cellulitis can also develop in skin that appears perfectly normal. Repeated infections often happen in areas where there is damage to the blood or lymph vessels that circulate fluid throughout the body. This damage can be caused by prior cellulitis infections, surgical removal of lymph nodes, removal of veins for vein grafts somewhere else in the body, and radiation to the area.

Cellulitis Appearance

Before skin changes occur, someone with cellulitis can have a fever, chills, and fatigue. The skin infection is usually red, swollen, warm to the touch, and painful. It's often difficult to tell exactly where the border is between normal and infected skin. Red streaks coming out of the area and swollen lymph nodes can sometimes occur.

Children often get cellulitis on the head and neck, and adults often get cellulitis on the arms or legs.

How Cellulitis Is Diagnosed

Cellulitis is usually diagnosed based on its typical appearance. Sometimes doctors check a blood count to see if the white blood cells are elevated, meaning the immune system is fighting off an infection.

Many times we don't see an elevated white blood cell count even though the immune system is busy fighting the infection. In people who are very sick, blood cultures might be done to see if bacteria have gotten into the blood stream. A cellulitis infection doesn't have pus that could be cultured to see what bacteria are involved.

Sometimes a doctor might do an "aspirate" which involves injecting sterile fluid into the infected tissue and drawing it back out, hoping that some of the bacteria get washed into the fluid. This fluid is then cultured to see what bacteria grow. An aspirate is usually done in unusual situations where there is a high chance that the infection is caused by a different bacteria than expected.

Cellulitis Treatment

Cellulitis is treated with antibiotics. Most cellulitis infections require 10 days of an oral antibiotic. If the infection is on an arm or especially a leg, elevating the extremity often speeds healing. IV antibiotics might be used in more severe cases such as:

  • Cellulitis of the face
  • Someone who is seriously ill
  • Infections in people who are immunocompromised
  • Infections that didn't improve or got worse with oral antibiotics

Preventing Cellulitis

The best prevention of cellulitis is taking good care of any break in the skin.

This can be done by:

  • Washing the wound daily with soap and water
  • Applying a topical antibiotic to the wound
  • Keeping it covered with a bandage to keep it clean
  • Changing the bandage every day or more often if the bandage gets dirty or wet

When to See the Doctor

It's time to have your doctor take a look if you're taking care of a wound as above and you notice that the wound is getting red, more painful, warm to the touch, or is draining. If you have diabetes, poor circulation, or are taking immune-suppressing medications, you should consider seeing your doctor as soon as you notice a wound. If not, you should go at the very first signs of infection.

Don't try to wait it out and see if it will get better on its own.


Habif, Thomas. "Bacterial Infections." Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 236-62.

Halpern, Analisa and Warren Heymann. "Bacterial Diseases." Dermatology. 2nd. Ed. Jean Bolognia. New York: Mosby, 2008: 1075-84.

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