Impetigo is a skin infection. It often appears as blisters around the mouth and nose, but it can infect skin anywhere on the body. Impetigo can easily spread from one person to another. This infection occurs most often in children.
Impetigo: Sores on the Upper Lip
Impetigo is caused by bacteria. The most common type of bacteria associated with this infection includes:
- Group A Streptococcus
These types of bacteria are normally found on the skin and in the nose. The bacteria do not cause trouble until it gets under the skin. Bacteria get in under the skin through small cuts, scratches, or insect bites.
This condition is more common in preschool and school-aged children.
Factors that increase your chance for impetigo include:
- Touching a person with impetigo
- Touching the clothing, towels, sheets, or other personal items that belong to a person with impetigo
- Poor hygiene, particularly unwashed hands and dirty fingernails
- Crowded settings where there is direct person-to-person contact, such as schools and the military
- Contact sports such as football and wrestling
- Warm, humid environment
- Summer season
- Poor health or weakened immune system
- Tendency to have skin problems such as eczema, poison ivy, or skin allergy
- Cuts, scratches, insect bites, or other injury to the skin
- Lice infections which cause scratching, such as scabies, head lice, or pubic lice
Symptoms of impetigo appear 4-10 days after contact with the bacteria.
The main signs of impetigo are skin lesions. They occur most often on the face, arms, or legs but can appear anywhere on the body. The lesions may be red spots, sores, or blisters. The lesion may:
- Ooze and become covered with a flat, dry, honey-colored crust
- Increase in size
- Spread, especially if scratched
There may also be swollen lymph nodes in the area with more serious infections.
Impetigo is normally a fairly mild condition. However, further problems could develop if it is not treated. The infection could spread. This can lead to pain, swelling, pus, or fever. Rarely, impetigo that is caused by Group A Streptococcus may develop into:
- Glomerulonephritis —damage to part of the kidney
- Scarlet fever—illness that may include a fever, sore throat, and widespread rash
- Life-threatening invasive streptococcal disease
You will be asked about your symptoms and medical history. The skin lesions will be examined. Your doctor will be able to diagnose impetigo by the look of your skin lesions.
A sample of the infected skin may be tested. This will show what specific bacteria are causing the infection. It may help to guide treatment choices.
The goals of treatment are to relieve the symptoms and cure the infection.
Treatment may include:
Antibiotics are a type of medication that can fight bacteria. For a mild infection, your doctor may advise:
- Prescription topical antibiotic
- Over-the-counter topical antibiotic—may be significantly less effective
- Topical antibiotics for the inside of the nose—bacteria can hide in the nose and make it easy for the infection to return
Your doctor may prescribe oral antibiotics for more severe or widespread infections.
In some cases, staphylococcal infections (such as MRSA) may be resistant to these antibiotics. Others options may be needed.
Good skin care is important with this type of infection. It can help prevent the spread of the infection to other areas of your skin or to others. In general:
- Do not touch or scratch the lesions.
- Wash the skin several times a day. Use soap and water or an antibiotic soap.
- The crusts may be removed by soaking the infected area. Place warm water on the area for about 15 minutes.
- Lesions should be covered loosely with gauze, a bandage, or clothing.
Avoiding Spread of the Infection
To help avoid spreading the infection:
- Wash your hands often and thoroughly. Make sure you wash under your fingernails where bacteria can hide. It is important to wash your hands after touching an infected area of your body.
- Avoid contact with newborn babies.
- Stay home until you have had treatment for 24 hours.
- Do not handle food at home until you have had treatment for at least 24 hours.
- If you work in the food service industry, ask your doctor when it is safe for you to return to work.
Prevention of impetigo involves good personal hygiene. The following tips can help:
- Bathe daily with soap and water.
- Wash your face, hands, and hair regularly.
- If caring for someone with impetigo, be sure to wash your hands each time you touch the person.
- Do not share towels, clothes, or sheets.
- Keep fingernails short and clean.
- Change and wash clothing often.
- Do not let your children play or have close contact with someone who may have impetigo.
- Wash wounds, such as cuts, scratches, or insect bites, with soap and water. Consider applying a small amount of antibiotic ointment. Cover the wound with a bandage.
American Academy of Dermatology
Kid's Health—Nemours Foundation
Canadian Dermatology Association
Impetigo. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated December 15, 2014. Accessed January 12, 2015.
Koning S, van der Wouden JC, et al. Efficacy and safety of retapamulin ointment as treatment of impetigo: randomized double-blind multicentre placebo-controlled trial. Br J Dermatol. 2008;158(5):1077-1082.
Impetigo fact sheet. Maryland Department of Health and Mental Hygiene website. Available at: http://ideha.dhmh.md.gov/IDEHASharedDocuments/impetigo.pdf. Updated April 2008. Accessed January 12, 2015.
10/6/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Hartman-Adams H, Banvard C. Impetigo: diagnosis and treatment. Am Fam Physician. 2014 Aug 15;90(4):229-235.
Last reviewed January 2015 by David L Horn, MD, FACP
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.