Ecthyma is a skin infection similar, to but more deeply invasive than impetigo.

Causes, incidence, and risk factors

The bacterium Streptococcus is the most common infectious organism associated with ecthyma. Staphylococcus bacteria can also cause ecthyma. The infection may start at the site of an injury, such as a scratch or insect bite, and is often found on the legs.

An ecthyma may begin with a pus-filled blister, similar to that seen in impetigo. However, the infection goes through the outer layer of skin (epidermis) and into the deeper layer (dermis). An ulcer with raised borders develops. It is covered by a hard crust. Unlike impetigo, ecthyma can sometimes result in scarring.


  • A small blister that may be pus-filled and has a reddish border  
  • A crusted ulcer that follows the appearance of the blister

Signs and tests

Examination by your health care provider is usually sufficient to diagnose ecthyma. Lesions may be skin biopsied or cultured in some instances.


Antibiotics to be taken by mouth are typically prescribed. Warm soaks (using a cloth soaked in warm tap water) are helpful for removing crusts. Antiseptic soap or peroxide washes of the lesion may be helpful in hastening recovery.

Expectations (prognosis)

Full recovery is expected.


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

Calling your health care provider

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


Cleanse all injuries or bites, and encourage your child to avoid scratching or digging at them.

Johns Hopkins patient information

Last revised: December 3, 2012
by Gevorg A. Poghosian, Ph.D.

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