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Impetigo (Impetigo Contagiosa)

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Medical Author:

Alan Rockoff, MD

Alan Rockoff, MD

Dr. Rockoff received his undergraduate degree from Yeshiva College with the distinction of Summa Cum Laude. He received his medical degree from the Albert Einstein College of Medicine. His internship and two years of Pediatric residency were at the Bronx Municipal Hospital Center, followed by training in Dermatology at the combined residency program at Tufts and Boston Universities. Dr. Rockoff is certified by both the American Board of Dermatology and the American Board of Pediatrics.

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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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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).

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

There are two kinds of impetigo:

• Non-bullous impetigo: This is the 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.

Is impetigo contagious?

Impetigo is contagious, mostly from direct contact with someone who has it but sometimes from towels, toys, clothing, or household items. After starting, 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 an infection at the nasal openings with prominent nasal drainage associated with a cold. The 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. Sometimes bacteria live in the nose and spread from there to other parts of the skin.

How is impetigo diagnosed?

Diagnosing impetigo is mostly straightforward based on the clinical appearance, though occasionally other conditions may look something like it. 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 diseases does occur sometimes. Medical judgment and occasionally culture tests, if necessary, are used to decide whether topical antibacterial creams will suffice or whether oral antibiotics will be necessary.