Ecthyma is most often caused by the streptococcus bacteria. Sometimes, staphylococcus bacteria cause this skin infection on its own or in combination with streptococcus.

The infection may start in skin that has been injured due to a scratch, rash, or insect bite. The infection often develops on the legs. People with diabetes or a weakened immune system are more prone to ecthyma.

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 with impetigo, but the infection spreads much deeper into the skin.

After the blister goes away, a crusty ulcer appears.

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

Your provider will usually prescribe antibiotics that you need to take by mouth (oral antibiotics). Very early cases may be treated with antibiotics that you apply to the affected area (topical antibiotics). Serious infections may need antibiotics given through a vein (intravenous antibiotics).

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

Ecthyma can sometimes result in scarring.

This condition may lead to:

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

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

Carefully clean the skin after an injury, such as a bite or scratch. Do not scratch or pick at scabs and sores.

Streptococcus - ecthyma; Strep - ecthyma; Staphylococcus - ecthyma; Staph - ecthyma; Skin infection - ecthyma

James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM. Bacterial infections. In: James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM, eds. Andrews' Diseases of the Skin: Clinical Dermatology. 13th ed. Philadelphia, PA: Elsevier; 2020:chap 14.

Pasternack MS, Swartz MN. Cellulitis, necrotizing fasciitis, and subcutaneous tissue infections. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 93.

Updated by: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.