– A superficial vesiculopustular infection of the skin found primarily on the arms, legs, and face. Ulcerative impetigo is called ecthyma.

Causes and Incidence

Impetigo is caused by staphylococci or streptococci transmitted by insect bite or directly from person to person through skin breaks. A secondary form of impetigo occurs with pediculosis, scabies, and fungal infections. Predisposing factors include poor hygiene, crowding, poor nutritional status, and frequent skin breaks. It is highly contagious in infants and small children, who are the most susceptible.

Disease Process

The bacteria colonize and incubate on the skin for as long as several weeks before initiation of the disease process. The lesions begin as small, erythematous macules beneath the stratum corneum that change to vesicles and then pustules, which rupture. In streptococcal impetigo, honey-colored crusts are formed, whereas in staphylococcal impetigo, light brown or clear crusts form. Individuals often have a mixture of both forms.


Intense itching, burning, and regional lymphadenopathy accompany the crusted skin lesions. Scratching often causes satellite lesions.

Potential Complications

Ecthyma is a deeper form of impetigo that affects the dermis as well as the epidermis and forms ulcers that later cause scarring. Glomerulonephritis is a severe complication that occurs in about 3% of impetigo cases.

Diagnostic Tests

The diagnosis is made by physical examination, Gram’s stain, and culture of the lesions.



Topical antiinfective drugs on lesions; systemic antiinfective drugs sensitive to causative agent; antipruritics for itching.

Crusts are washed with soap and water, and cool, moist compresses are applied; isolation until lesions have healed; careful personal and family hygiene; protective devices (e.g., mittens, distractions) to reduce scratching; nails kept trimmed; nutritional therapy if needed; treatment of any underlying disease processes.