Impetigo

Medical Author : John Mersch, MD, FAAP

Medical Editor : William C. Shiel Jr., MD, FACP, FACR

A boy with impetigo.

 

Impetigo facts

  • Impetigo is a bacterial infection of the surface of the skin.
  • Impetigo is more common in children than in adults.
  • The two types of impetigo are non-bullous and bullous impetigo.
  • Impetigo symptoms and signs include
    • small blisters,
    • dark or honey-colored crust that forms after the pustules burst.
  • Impetigo is contagious and is caused by strains of both staph and strep bacteria.
  • Impetigo is not serious and is easy to treat with either prescription topical or oral antibiotics. Scarring is very rare.
    Illustrations of Staphylococcus (staph) and Streptococcus (strep) bacteria.

    What is impetigo? What causes impetigo?

    Impetigo (pronounced im-puh-TIE-go) is a contagious, superficial infection of the skin caused by Staphylococcus (staph) and Streptococcus (strep) bacteria. Impetigo is more common in children (especially 2- to 5-year-olds) than in adults. Impetigo is most likely to occur in warm and humid environments and is most commonly spread by close contact (such as family members).
    Examples of non-bullous (left) and bullous impetigo (right).

    What are the types of impetigo? What are impetigo symptoms and signs? What does impetigo look like?

    There are two forms of impetigo:

    • Non-bullous impetigo: This is the more common form, caused by both staph and strep bacteria. This form initially presents as small red papules similar to insect bites. These lesions rapidly evolve to small blisters and then to pustules that finally scab over with a characteristic honey-colored crust. This entire process usually takes several days. These lesions often start around the nose and on the face, but less frequently they may also affect the arms and legs. At times, there may be non-tender but swollen lymph nodes (glands) nearby.
    • Bullous impetigo: This form of impetigo is caused only by staph bacteria. These bacteria produce a toxin that reduces cell-to-cell stickiness (adhesion) causing separation between the top skin layer (epidermis) and the lower layer (dermis). This leads to the formation of a blister. (The medical term for blister is bulla.) Bullae can appear in various skin areas, especially the buttocks and trunk. These blisters are fragile and contain a clear yellow-colored fluid. The bullae are delicate and often break and leave red, raw skin with a ragged edge. A dark crust will commonly develop during the final stages of development. With healing, this crust will resolve.Because it is contagious, children can get impetigo from direct contact, sharing towels, or sharing toys as examples.
       

      Is impetigo contagious?

      Impetigo is contagious, primarily from direct contact with someone who has it but sometimes from towels, toys, clothing, or household items. Impetigo often spreads to other parts of the body. This is particularly common with impetigo in children. There may be mini epidemics in day-care centers. Bacteria that cause impetigo may enter through a break in the skin, such as that which comes from cuts and scrapes. A common toddler impetigo experience is the development of impetigo at the nasal openings inflamed by the prominent nasal drainage associated with a cold. In this situation, skin integrity is often disrupted by the continuous covering of purulent nasal discharge. Adults often develop impetigo from close contact with infected children. Heat, humidity, and the presence of eczema predispose a person to developing impetigo. Recurrent impetigo infections may be associated with staph or strep bacteria residing in the nose and spreading from to other parts of the skin.
      A doctor checking a boys face for impetigo.

      How is impetigo diagnosed?

      Diagnosing impetigo is generally straightforward and based on the clinical appearance. Occasionally, other conditions may look something like impetigo. Infections such as tinea ("ringworm") or scabies (mites) may be confused with impetigo. It is important to note that not every blister means an impetigo infection. At times, other infected and noninfected skin diseases produce blister-like skin inflammation. Such conditions include herpes cold sores, chickenpox, poison ivy, skin allergies, eczema, and insect bites. Secondary infection of these other skin lesions may sometimes occur. Medical evaluation and occasionally culture tests are used to decide whether topical antibacterial creams will suffice or whether oral antibiotics will be necessary.
      A father putting ointment on a boys face.

      What is the treatment for impetigo?

      Impetigo is not serious and is very treatable. Mild impetigo can be handled by gentle cleansing, removing crusts, and applying the prescription-strength antibiotic ointment mupirocin (Bactroban). Nonprescription topical antibiotic ointments (such as Neosporin) generally are not effective. More severe or widespread impetigo, especially of bullous impetigo, may require oral antibiotic medication. In recent years, more staph germs have developed resistance to standard antibiotics. Bacterial culture tests can help guide the use of proper oral therapy if needed. Antibiotics which can be helpful include penicillin derivatives (such as amoxicillin and clavulanic acid [Augmentin]) and cephalosporins such as cephalexin (Keflex). If clinical suspicion supported by culture results show other bacteria, such as drug-resistant staph (methicillin-resistant Staphylococcus aureus or MRSA), other antibiotics such as clindamycin or trimethoprim-sulfamethoxazole (Bactrim or Septra) may be necessary. Treatment is guided by laboratory results (culture and sensitivity tests).

    Washing hands with soap and water can help prevent the spread of impetigo.

    What are possible complications of impetigo?

    One potentially serious, but rare, complication of impetigo caused by strep bacteria is glomerulonephritis, a condition producing kidney inflammation. Many specialists are not convinced that treating impetigo will prevent glomerulonephritis from occurring.

    Will impetigo leave scars?

    Because the crusts and blisters of impetigo are superficial, impetigo generally does not leave scars. Affected skin looks red for a while after the crusts go away, but this redness fades in a matter of days to weeks.

    Can impetigo be prevented?

    Routine hand washing with soap and warm water is an important and effective mechanism to prevent the spread of impetigo.

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