Impetigo is a skin disorder caused by bacterial infection and characterized by crusting skin lesions.

Causes, incidence, and risk factors

Impetigo is a common skin infection. It is most common in children, particularly children in unhealthy living conditions. In adults, it may follow other skin disorders. Impetigo may follow a recent upper respiratory infection such as a cold or other viral infection.

It is similar to cellulitis, but is more superficial, involving infection of the top layers of the skin with streptococcus (strep), staphylococcus (staph), or both.

The skin normally has many types of bacteria on it, but intact skin is an effective barrier that keeps bacteria from entering and growing within 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 insect bites, animal bites, or human bites; or other injury or trauma to the skin. Impetigo may occur on skin where there is no visible break.

Impetigo begins as an itchy, red sore that blisters, oozes and finally becomes covered with a tightly adherent crust. It tends to grow and spread. Impetigo is contagious. The infection is carried in the fluid that oozes from the blisters. Rarely, impetigo may form deeper skin ulcers.


  • Skin lesion on the face/ lips, or on the arms or legs, spreading to other areas. Typically this lesion begins as a cluster of tiny blisters which burst, followed by oozing and the formation of a thick honey or brown colored crust that is firmly stuck to the skin.  
  • Itching blister:       o Filled with yellow or honey-colored fluid       o Oozing and crusting over  
  • Rash (may begin as a single spot, but if child digs at it, it may spread to other areas).  
  • In infants, a single or possibly multiple blisters filled with pus, easy to pop and when broken leave a reddish raw-looking base.  
  • Lymphadenopathy - local lymph nodes near the infection may be swollen.

Signs and tests
Diagnosis is based primarily on the appearance of the skin lesion. A culture of the skin or mucosal lesion usually grows streptococcus or staphylococcus.


The goal is to cure the infection and relieve the symptoms.

A mild infection is typically treated with a prescription antibacterial cream such as Bactroban. Oral antibiotics (such as erythromycin or dicloxacillin) are also frequently prescribed and result in rapid clearing of the lesions.

Wash the skin several times a day, preferably with an antibacterial soap, to remove crusts and drainage.

Prevent the spread of infection. Use a clean washcloth and towel each time. Do not share towels, clothing, razors, and so on with other family members. Wash the hands thoroughly after touching the skin lesions.

Expectations (prognosis)
The sores of impetigo heal slowly and seldom scar. The cure rate is extremely high, but they often come back in young children.


  • The infection could spread to other parts of the body. This is common.  
  • Children often have multiple patches of impetigo.  
  • A systemic infection could lead to kidney failure (post-streptococcal glomerulonephritis). This is a rare occurrence.  
  • Permanent skin damage and scarring (also extremely rare).

Calling your health care provider
Call for an appointment with your health care provider if symptoms indicating impetigo are present.

Good general health and hygiene help to prevent infection. Minor abrasions or areas of damaged skin should be thoroughly cleansed with soap and clean water. A mild antibacterial agent may be applied if desired.

Impetigo is contagious, so avoid skin contact with drainage from impetigo lesions.

Johns Hopkins patient information

Last revised: December 8, 2012
by Armen E. Martirosyan, M.D.

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