Definition

Impetigo is a highly contagious skin infection. It is caused by bacteria.

Impetigo: Sores on the Upper Lip

Nucleus factsheet image
© 2009 Nucleus Medical Art, Inc.

Causes

Impetigo is caused by one or both of the following types of bacteria:

  • Group A Streptococcus
  • Staphylococcus

These bacteria are normally found on the skin and in the nose. When small cuts, scratches, or insect bites occur, these bacteria can get under the skin. There they can cause infection. Impetigo is often spread from person to person.

Risk Factors

Factors that increase your chance for impetigo include:

  • Age: preschool and school-aged children
  • Touching a person with impetigo
  • Touching the clothing, towels, sheets, or other items of 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
  • Warm, humid environment
  • Seasonal: Summer
  • 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 or trauma to the skin
  • Chickenpox
  • Lice infections (like scabies , head lice , or public lice ), which cause scratching

Symptoms

Symptoms of impetigo appear 4-10 days after exposure.

Symptoms may include:

  • Red spots, sores, or blisters, present on the skin of the face, arms, legs or other parts of the body, that:
    • Ooze and become covered with a flat, dry, honey-colored crust
    • Itch
    • May increase in size
    • Spread, especially if scratched
  • Swollen lymph nodes, in more serious cases

Normally, impetigo is a fairly mild condition. However, if left untreated, further problems could develop. This can include pain, swelling, spread of infection, discharge of pus, or fever. In rare cases, people whose impetigo is caused by Group A Streptococcus may develop:

Diagnosis

The doctor will examine your skin lesions. Your doctor will also ask about your symptoms and medical history. Initial diagnosis is based on the appearance of your skin lesions.

If you have impetigo, a culture of the skin lesion may be done. This will show what specific bacteria are involved.

Treatment

The goals of treatment are to relieve the symptoms and cure the infection.

Treatment may include:

Antibiotics

For a mild infection:

  • Prescription topical antibiotic (eg mupirocin , retapamulin )
  • Over-the-counter topical antibiotic (significantly less effective), such as neomycin, bacitracin , or polymyxin

Your doctor may prescribe oral antibiotics, such as:

In some cases, staphylococcal infections (eg, MRSA ) may be resistant to these antibiotics. Others options may be needed.

Skin Care

Do not touch or scratch the lesions. The skin should be washed several times a day. Use soap and water or an antibiotic soap. The crusts may be removed by soaking the infected area in warm water 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 thoroughly, especially after touching an infected area of your body.
  • Avoid contact with newborn babies.
  • Stay home until 24 hours after the start of treatment.
  • Do not handle food at home until a minimum of 24 hours after the start of treatment.
  • If you work in the food service industry, ask your doctor when it is safe for you to return to work.

Prevention

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 after each time you touch the person.
  • Do not share towels, clothes, or sheets. This is more important with a person who has impetigo.
  • Keep fingernails short and clean.
  • Change and wash clothing frequently.
  • Do not let your children play or have close contact with someone who may have impetigo.
  • Promptly wash wounds, such as cuts, scratches, or insect bites, with soap and water. Consider applying a small amount of antibiotic ointment, and cover the wound with a bandage.