Ecthyma is a skin infection similar to impetigo. It is often called "deep impetigo" because it occurs deep inside the skin.

Ecthyma is most often caused by the bacteria streptococcus. Sometimes, staphylococcus bacteria causes this skin infection.

The infection may start in skin that has been injured due to a scratch or insect bite. It often develops on the legs.

The main symptom of ecthyma is a small blister with a red border that may be filled with pus. The blister is similar to that seen in persons with impetigo, but the infection spreads much deeper into the skin.

After the blister goes away, a crusty ulcer appears.

Your doctor can usually diagnose this condition simply by looking at your skin. In rare cases, the fluid inside the blister may be sent to a lab for closer examination or a skin biopsy may be done.

Your doctor will usually prescribe antibiotics by mouth (oral antibiotics). Very early cases may be treated with topical medications. More advanced forms may need antibiotics given through a vein (intravenous antibiotics).

Placing a warm wet cloth over the area can help remove ulcer crusts. Your doctor may recommend antiseptic soap or peroxide washes to speed recovery.

Unlike impetigo, ecthyma can sometimes result in scarring.

• Spread of infection to other parts of the body
• Permanent skin damage with scarring

Make an appointment with your health care provider if you have symptoms of ecthyma.

Carefully clean the skin after an injury (such as a bite or scratch). Avoid scratching or digging at scabs and sores.

Habif TP. Clinical Dermatology. 4th ed. St. Louis, Mo: Mosby; 2004.

Mandell GL, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 6th ed. London: Churchill Livingstone; 2005.

Rakel RE. Textbook of Family Practice. 6th ed. Philadelphia, Pa: WB Saunders; 2002.