Highly Contagious Bacterial Skin Infection

Impetigo is a common skin infection caused by Staphylococcus or Streptococcus bacteria. Although these bacteria are found on uninfected skin, each can cause an infection under certain circumstances. Impetigo often develops in young children and commonly involves the skin around the mouth and nose. It can develop around a break in the skin caused by an insect bite or cut, but it can also occur on healthy, intact skin. 

The rash of impetigo usually appears as a group of tiny red sores or blisters that itch. The sores ooze and eventually become covered with a clear yellow crust. This yellow fluid is contagious, and scratching the sores can transmit the infection to other areas of the body or to other people. Scratching the area of skin involved can worsen the inflammation and even lead to a more serious infection of the tissues under the skin surface. 

Impetigo is very contagious, spreading easily to other areas of the body or to other persons in close proximity. The spread can occur by direct skin-to-skin contact or by indirect contact through contaminated materials, especially under moist or unsanitary conditions. 

Mild cases of impetigo can be treated by washing the area with an antibacterial soap and warm water several times each day to remove the crusty areas, then applying an antibiotic ointment and a nonstick dressing, if needed. In more severe cases that involve tissue below the skin surface, an oral antibiotic may be prescribed. Methicillin-resistant staphylococcus aureus (MRSA) is a recently observed strain that is resistant to certain antibiotics. Impetigo infections caused by MRSA require special antibiotic therapy for successful treatment. 

Impetigo can be prevented by practicing good hygiene and keeping minor scrapes clean and protected to avoid infection. To avoid the spread of the bacteria that cause impetigo, personal care items such as washcloths, towels, and razors should not be shared with family or friends. Most impetigo infections clear up over time and heal without scarring. 

Because the Infection Is Common in Young Children, Good Hygiene Is Key

The two specific strains of bacteria responsible for most cases of impetigo are Staphylococcus aureus and Streptococcus pyogenes. These bacteria are present on healthy skin and do not cause infection in most people. In adults, impetigo does not develop unless there is a break in the skin, although young children may develop impetigo on skin that is intact. People with chronic dermatitis, an inflammation of the skin from allergy or other causes, are more likely to develop impetigo. 

Avoiding Outbreaks

Impetigo is most common in patients under 6 years old and those who spend much of the day with others in close quarters, such as in day care centers or schools. Athletes in contact sports like wrestling also have a greater chance of developing impetigo. High humidity increases the likelihood of spread, so outbreaks of impetigo are often seen in warm climates, during the summer months, or among athletes in locker rooms. The bacteria are spread through skin-to-skin contact and on moist articles, such as towels or clothing. 

The diagnosis of impetigo is made by a visual examination of the affected area, along with a history that might include the cause of damage to the skin and any other symptoms of infection. Lymph nodes near the affected area may be tender or swollen. In more severe cases, a culture of a small amount of the drainage from the sores or blisters is performed to determine if bacteria are present and which antibiotics will be effective to treat the infection. 

Treatment With Antibiotics

The goal of impetigo therapy is to heal the area quickly, avoid scarring or further infection, and stop the potential spreading of this highly contagious condition to other areas of the body or other people. The affected area should be gently cleaned with warm water and soap several times a day, and an OTC or prescription antibiotic ointment may be applied. Depending on the location of the rash, a sterile gauze dressing may also be recommended to protect the area as it heals and to avoid further spread. If the infection is more severe or widespread, the use of an oral antibiotic is appropriate. 

If you or someone you have contact with is diagnosed with impetigo, be sure to avoid sharing any articles that could help spread the bacteria. Children diagnosed with impetigo can return to school or day care after they are no longer contagious, usually 1 to 2 days after beginning antibiotic therapy. 

In most cases, impetigo heals in 2 to 3 weeks without long-term damage to the affected area, and scarring is not seen unless the infection becomes deep-seated. However, a rare complication of impetigo caused by the Streptococcus bacterium is an inflammation of the kidneys known as poststreptococcal glomerulonephritis. This kidney inflammation causes symptoms 10 to 14 days after the streptococcal infection, including facial swelling, urinary symptoms, and stiff joints. 

If you have questions about impetigo, your pharmacist can advise you on the proper use of topical or oral antibiotics used to treat the infection. 

To comment on this article, contact rdavidson@uspharmacist.com.