Doctor K: Bacteria under skin troublemaker

DEAR DOCTOR K: My son developed a large, red, swollen area on his arm. The doctor called it cellulitis. My son is better now, but I’d like to learn more about cellulitis.

DEAR READER: Cellulitis is a serious bacterial infection of the skin. Bacteria live on the surface of our skin, but the skin is built to keep the bacteria from getting inside us. If they get beneath the surface of the skin, and then into the tissues below the skin, they can make trouble.

When our skin gets injured, bacteria can break through the skin’s protective outer layer. This typically happens at the site of an injury, such as a cut, puncture, sore, burn or bite. It’s even more likely if we have had recent surgery that cut through the skin, or have a catheter carrying medicines into a vein. Other things that make a person vulnerable to cellulitis are edema, poor blood flow, or a skin rash that creates breaks in the skin.

Once beneath the skin’s surface, bacteria multiply. They make chemicals that cause inflammation. Cellulitis is the most common type of bacterial infection.

With cellulitis, the affected skin feels warm and is usually red, swollen and painful. There may be a spreading network of red streaks in the skin.

Many types of bacteria can cause cellulitis. The most common are streptococcus (“strep”) and staphylococcus (“staph”). Cellulitis is treated with antibiotics. Doctors don’t need to identify which specific bacteria caused the infection. They can prescribe a “broad spectrum” antibiotic that will treat most types of bacteria that cause cellulitis. In most cases, cellulitis improves within two days after antibiotics are started.

If you have mild cellulitis, you can usually treat it at home with antibiotics taken by mouth. Applying warm compresses and elevating the infected area can help. If you have severe cellulitis, you may need to be treated with antibiotics intravenously. To help prevent cellulitis:

• Prevent skin injury.

• Treat minor skin wounds promptly.

• Contact your doctor to treat all deep wounds and animal bites.

• Call your doctor whenever a skin injury becomes red, warm, swollen or tender.