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Impetigo: Diagnosis and treatment

How do dermatologists diagnose impetigo?

A dermatologist can often diagnose impetigo by looking at your skin.

Sometimes, lab tests are necessary to give you the diagnosis, or to get information necessary to treat you. If you need a lab test, a dermatologist often takes a sample from a blister on your skin. This can tell your dermatologist which bacteria are causing the infection.

If your dermatologist thinks that the infection could be widespread, you may need a blood test.

How do dermatologists treat impetigo?

An antibiotic usually cures impetigo.

Dermatologists often prescribe an antibiotic that you apply to the skin, such as mupirocin or retapamulin. The Food and Drug Administration (FDA) has approved retapamulin to treat impetigo in children as young as 9 months old. Mupirocin is FDA approved to treat people 12 years of age and older.

When necessary, a dermatologist may prescribe one of these medicines to treat a child younger than the FDA-approved age. This is called off-label use and is legal. It can also be very helpful.

If a dermatologist prescribes an antibiotic you apply to the skin, you would apply it to the skin with impetigo. If you have several outbreaks of impetigo, you may need to apply it inside the nostrils. The bacteria that cause impetigo often thrive in the nostrils.

Sometimes stronger medicine is necessary. Your dermatologist can prescribe an antibiotic that you take by mouth. A few patients need injections of an antibiotic.

Skin care also plays an important role in clearing impetigo. The following steps are often very helpful:

  1. Soak the skin with impetigo in warm water and soap to gently remove dirt and crusts

  2. Apply the antibiotic (or other medicine) as prescribed

  3. Cover the skin with impetigo to help it heal and prevent spreading the infection to others

If a child gets impetigo frequently, your dermatologist may recommend adding a small amount of bleach to the child’s bath. This is completely safe when you follow the directions. A bleach bath can reduce the amount of bacteria on the skin, which may prevent new infections.

Because impetigo is very contagious, a child may need to stay home from school for a few days. If this is necessary, your dermatologist will tell you when your child can return to school.

Teens and adults need not stay home, but they should take the following precautions to avoid infecting others:

  • Avoid direct skin-to-skin contact with others

  • Keep blisters and sores covered with gauze bandages and tape

  • Wash their hands after touching or treating infected skin

Your dermatologist can tell you how long to take these precautions.


Dermatologists recommend treating impetigo. It can help cure the impetigo and prevent others from getting this highly contagious skin infection.

With treatment, impetigo is usually no longer contagious within 24 to 48 hours.

Without treatment, impetigo often clears on its own in two to four weeks. During this time, there is a greater risk of developing complications. You may see new blisters and sores.

It’s also possible for the infection to go deeper into the skin if you don’t treat. If this happens, you can develop ecthyma. This infection goes deeper into the skin than impetigo. As the skin heals from ecthyma, scars can form.

Ecthyma is more common in children, the elderly, and people who have diabetes. It also develops in the homeless and combat soldiers fighting in a hot and humid climate.

If you see anything on your skin that looks infected, it’s best to see a board-certified dermatologist as soon as possible. An early diagnosis and treatment can prevent complications and help you feel better.

Craft, N, Lee PK, et al. “Superficial cutaneous infections and pyodermas.” In: Wolff K, Goldsmith LA, et al. Fitzpatrick’s Dermatology in General Medicine (seventh edition). McGraw Hill Medical, New York, 2008: 1695-8.

Habif TP, Campbell, JL, et al. “Impetigo.” In: Dermatology DDxDeck. Mosby Elsevier, China, 2006: Card#46.

Halpern AV and Heymann WR. “Bacterial diseases.” In: Bolognia JL, et al. Dermatology. (second edition). Mosby Elsevier, Spain, 2008:1075-6.

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