Dr. Jeff Hersh: Can siblings share impetigo?

Q: My 7-year-old developed a rash on his buttocks, which spread over the next couple of days. His pediatrician said it was impetigo. Now his sister is developing a rash. Could this also be impetigo?

A: Impetigo is a common skin infection, responsible for over 10 percent of all skin problem complaints that present to pediatric clinics. It is contagious, and is spread by direct or indirect contact -- such as touching a contaminated object. So it is likely your daughter also has impetigo, although you should check with your pediatrician to be sure.

Because it is so contagious, it is common that there are outbreaks of impetigo in day care and/or other settings where there is close contact between people, especially kids.

There are two types of impetigo, bullous and non-bullous.

Bullous impetigo, characterized by large painless bullae (fluid filled blisters), is the less common type, accounting for only 30 percent of all cases. Over 90 percent of these are in children under the age of 2.

Bullous impetigo is due to a toxin made by the bacteria staph aureus which causes an inflammatory reaction that leads to a build-up of fluid between layers of the skin.

The bullae are usually itchy, and are most common on the trunk (especially the buttocks), arms or legs. The inflammation fluid spills out when the fragile bullae break.

The more common non-bullous impetigo -- responsible for 70 percent of impetigo cases -- is usually due to group A beta-hemolytic strep, the same strain that causes strep throat (although other types of strep or staph can also cause it). It is most common in children between the ages of 2 and 6.

It typically affects the surface layers of the skin around the mouth or nose (although it can affect any other area of the body) causing red, raised lesions that develop into small blisters that ooze for a couple of days and then crust over, becoming a honey-colored, dry, crusty rash. The child may have swollen glands, but does not typically have systemic symptoms such as fever.

When newborns get non-bullous impetigo it is most often due to group B strep (which is a common bacteria found in the mom's vagina) or staph aureus (a bacteria that is on some people's skin without causing infection, with these people being called carriers).

The diagnosis of impetigo is made based on the history and physical exam, and no further testing is usually required.

Although impetigo would usually resolve within two to three weeks even without medications, it resolves faster with appropriate medical care.

The first step in treating impetigo is gentle cleaning of the infected area. Deep scrubbing is not required, and can be painful for the patient. For infections confined to one area of the body, or a couple of small areas, an antibiotic cream (called mupirocin) is very effective.

More widespread infections will require antibiotics by mouth, and your doctor will chose ones that are effective against strep and staph since those are the causative organisms.

Unfortunately, a small number of impetigo infections have complications. These can include spread of the infection to deeper tissues or the joints, bone or the blood, becoming a systemic infection. Patients with these more invasive infections usually require hospitalization and intravenous antibiotics. Other complications can also occur from an impetigo infection, including a kidney disease that can occur after a strep infection (glomerulonephritis), and possibly (the literature is not clear on this) rheumatic fever.

Despite these uncommon complications, the overall prognosis of impetigo is very good, with complete recovery. Since, in most cases, impetigo only affects the top layers of skin, there is usually no scarring once it heals.

Impetigo is not an infection that needs to be reported to local health authorities, but the school nurse (or school or day-care supervisors) should be aware so they can ensure shared toys between children are thoroughly washed and that other parents are made aware that the infection has been noted in the facility.

If your child has symptoms suggestive of impetigo they should see their health care provider to verify the diagnosis and to begin appropriate treatment to shorten the duration of the illness. Recommendations to prevent spread of this contagious infection will also be made, typically keeping the child out of school (or day care) until they are no longer contagious.

Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.