Disease Fact Sheet Series:

What is impetigo?
Impetigo is an infection of the skin caused primarily by the bacterium Streptococcus pyogenes, also known as Group A beta-hemolytic streptococci (GABS). Sometimes another bacterium, Staphylococcus aureus, can also be isolated from impetigo lesions.

What are the symptoms of impetigo?
Impetigo begins as a cluster of small blisters that expand and rupture within the first 24 hours. The thin yellow fluid that drains from the ruptured blisters quickly dries forming a honey-colored crust. Impetigo develops most frequently on the legs, but may also be found on the arms, face and trunk. There is usually no fever.

How does a person get impetigo?
Impetigo may develop after the skin is infected with GABS. The bacterium is usually acquired from skin-to-skin contact with another person with impetigo. Less commonly, impetigo may develop when open skin lesions (such as insect bites or burns) are infected following exposure to a person with streptococcal pharyngitis ("strep throat").

Who gets impetigo?
The infection is most common in settings where there is crowding or activities leading to close person-to-person contact such as in schools and military installations. Impetigo occurs more commonly during the summer and early fall.

How long does it take to develop impetigo following exposure?
Impetigo may develop up to 10 days after the skin becomes infected with GABS.

How is impetigo treated?
Impetigo may be treated with an antibiotic taken by mouth or by application of an antibiotic ointment to the affected areas.

How long is a person considered infectious?
A person with impetigo is probably no longer infectious after 24 hours of adequate antibiotic treatment. Without treatment, a person may be infectious for several weeks.

What are the complications of impetigo?
Rarely, GABS may invade beyond the skin of a person with impetigo and cause more serious illnesses. Persons with impetigo may also develop post-streptococcal scarlet fever, or glomerulonephritis, a condition that may result in temporary kidney failure. Post-streptococcal glomerulonephritis follows roughly 10 days after the onset of streptococcal infection. However, the long-term prognosis is excellent. Scarlet fever is caused by a toxin produced by certain strains of GABS and is characterized by high fever, chills, sore throat, headache, vomiting and a fine red rash.

What can be done to prevent impetigo?
Simple cleanliness and prompt attention to minor wounds will do much to prevent impetigo. Persons with impetigo or symptoms of GABS infections should seek medical care and if necessary begin antibiotic treatment as soon as possible to prevent spread to others. Individuals with impetigo should be excluded from school, day care, or other situations where close person-to-person contact is likely to occur until at least 24 hours after beginning appropriate antibiotic therapy. Sharing of towels, clothing, and other personal articles should be discouraged.

For more information, contact your
Local Public Health Department

PDF: The free Acrobat Reader^® software is needed to view and print portable document format (PDF) files.  Learn more

Last Revised: June 22, 2011