Diseases & Conditions

Impetigo

Impetigo (im-puh-TIE-go) is a highly contagious skin infection that mainly affects infants and children. Impetigo usually appears as red sores on the face, especially around a child's nose and mouth. Although it commonly occurs when bacteria enter the skin through cuts or insect bites, it can also develop in skin that's perfectly healthy.

Impetigo is seldom serious, and usually clears on its own in two to three weeks. But because impetigo can sometimes lead to complications, your child's doctor may choose to treat impetigo with an antibiotic ointment or oral antibiotics. Your child can usually return to school or a child care setting as soon as he or she isn't contagious — often within 24 hours of starting antibiotic therapy.

The following are signs and symptoms of impetigo:

• Red sores that quickly rupture, ooze for a few days and then form a yellowish-brown crust
• Itching
• Painless, fluid-filled blisters
• In the more serious form, painful fluid- or pus-filled sores that turn into deep ulcers

Types of impetigo

• Impetigo contagiosa. The most common form of impetigo is impetigo contagiosa, which usually starts as a red sore on your child's face, most often around the nose and mouth. The sore ruptures quickly, oozing either fluid or pus that forms a honey-colored crust. Eventually the crust disappears, leaving a red mark that heals without scarring. The sores may be itchy, but they aren't painful.

  Your child isn't likely to have a fever with this type of impetigo but may have swollen lymph nodes in the affected area. And because it's highly contagious, just touching or scratching the sores can spread the infection to other parts of the body.

• Bullous impetigo. This type primarily affects infants and children younger than 2 years. It causes painless, fluid-filled blisters — usually on the trunk, arms and legs. The skin around the blister is usually red and itchy but not sore. The blisters, which break and scab over with a yellow-colored crust, may be large or small, and may last longer than sores from other types of impetigo.
• Ecthyma. This more serious form of impetigo penetrates deeper into the skin's second layer (dermis). Signs and symptoms include painful fluid- or pus-filled sores that turn into deep ulcers, usually on the legs and feet. The sores break open and scab over with a hard, thick, gray-yellow crust. Scars can remain after the sores heal. Ecthyma can also cause swollen lymph glands in the affected area.

When to see a doctor
If you suspect that you or your child has impetigo, consult your family doctor, your child's pediatrician or a dermatologist. Your doctor can recommend a treatment plan based on the type of impetigo and severity of the infection.

Two types of bacteria cause impetigo — Staphylococcus aureus (staph), which is most common, and Streptococcus pyogenes (strep). Both types of bacteria can live harmlessly on your skin until they enter through a cut or other wound and cause an infection.

In adults, impetigo is usually the result of injury to the skin — often by another dermatological condition such as dermatitis. Children are commonly infected through a cut, scrape or insect bite, but they can also develop impetigo without having any notable damage to the skin.

You're exposed to the bacteria that cause impetigo when you come into contact with the sores of someone who's infected or with items they've touched, such as clothing, bed linen, towels and even toys. Once you're infected, you can easily spread the infection to others.

Staph bacteria produce a toxin that causes impetigo to spread to nearby skin. The toxin attacks a protein that helps bind skin cells together. Once this protein is damaged, bacteria can spread quickly.

Doctors usually diagnose impetigo by considering signs and symptoms and medical history and looking at the distinctive sores. Your doctor will likely ask about any recent cuts, scrapes or insect bites to the affected area.

A culture may be necessary to confirm the diagnosis or to rule out another cause. During this test, your doctor uses a sterile swab to gently remove a small bit of pus or drainage from one of the sores. The sample is then cultured in a laboratory for the presence of bacteria.