Impetigo (Impetigo Contagiosa)
Medical Author: Alan Rockoff, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
What is impetigo? What causes it?
Impetigo (pronounced im-puh-TIE-go) is an infection of the surface of the skin, caused by staphylococcus ("staph") and streptococcus ("strep") bacteria. Impetigo is more common in children than in adults.
What are the types and symptoms of impetigo? What does impetigo look like?
The two kinds of impetigo are:
- Non-bullous impetigo: This is the common form, caused by both staph and strep
bacteria. It appears as small blisters or scabs, which then form yellow or honey-colored crusts. These often start around the nose and on the face, but
they also may affect the arms and legs. At times, there may be swollen glands nearby.
- Bullous impetigo: This form is caused by staph bacteria that produce a toxin that causes a break between the top layer (epidermis) and the lower levels of skin forming a blister. (The medical term for blister is bulla.) Blisters can appear in various skin areas, especially the buttocks, though these blisters are fragile and often break and leave red, raw skin with a ragged edge. No prior trauma is needed for these blisters to appear.
Is impetigo contagious?
Impetigo is contagious, mostly from direct contact with someone who has it, but sometimes from towels, toys, clothing or household items. Once it starts, impetigo often spreads to other parts of the body. This is particularly common with impetigo in children. There may be mini epidemics in daycare centers. Bacteria that cause impetigo may enter through a break in the skin, such as that which comes from cuts and scrapes. At times, however, impetigo appears even if no one nearby has it and the skin seems unbroken. Adults often catch 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, though occasionally other conditions may look something like it, such as tinea (fungus, "ringworm") or scabies (mites). It is important to note that not every blister or ooze means infection. At times, other infected and noninfected skin diseases produce blister-like skin inflammation. Such conditions include herpes cold sores, chickenpox, poison ivy, other skin allergies, eczema, and insect bites. Secondary infection of these diseases does occur sometimes, but often blistering comes from the original condition and does not mean that actual impetigo has developed. Medical judgment
-- helped by culture tests, when necessary -- is needed to decide whether antibacterial creams or pills should be used in addition to the remedies suitable for the original condition.
Next: What is the treatment for impetigo? »
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