Impetigo (Impetigo Contagiosa)

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Medical Author:

John Mersch, MD, FAAP

John Mersch, MD, FAAP

Dr. Mersch received his Bachelor of Arts degree from the University of California, San Diego, and prior to entering the University Of Southern California School Of Medicine, was a graduate student (attaining PhD candidate status) in Experimental Pathology at USC. He attended internship and residency at Children's Hospital Los Angeles.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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• 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 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.

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).

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 takes about one week. 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 swollen but non-tender 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.