Impetigo is a common skin infection.

Impetigo is caused by streptococcus (strep) or staphylococcus (staph) bacteria. Methicillin-resistant staph aureus (MRSA) is becoming a common cause.

The skin normally has many types of bacteria on it, but intact skin is an effective barrier that keeps bacteria from entering and growing in the body. When there is a break in the skin, bacteria can enter the body and grow there, causing inflammation and infection. Breaks in the skin may occur with:

• Animal bites
• Human bites
• Injury or trauma to the skin
• Insect bites

Impetigo may also occur on skin where there is no visible break.

It is most common in children, particularly those in unhealthy living conditions.

In adults, it may follow other skin disorders or a recent upper respiratory infection such as a cold or other virus. It is similar to cellulitis, but it only involves the top layers of the skin.

Impetigo is contagious. The infection is carried in the fluid that oozes from the blisters.