Merck Manual

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Puss Moth Caterpillar Stings

(Asp Stings)

By

Robert A. Barish

, MD, MBA, University of Illinois at Chicago;


Thomas Arnold

, MD, Department of Emergency Medicine, LSU Health Sciences Center Shreveport

Last full review/revision May 2020| Content last modified May 2020
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NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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The venomous puss moth caterpillar (Megalopyge opercularis; also called the asp) is present in the southern United States. It is teardrop shaped and has long silky hair, making it resemble a tuft of cotton or fur.

When a puss moth caterpillar rubs or is pressed against a person’s skin, its venomous hairs are embedded, usually causing severe burning and a rash. Pain usually subsides in about an hour.

Occasionally, the reaction is more severe, causing swelling, nausea, and difficulty breathing.

Treatment

  • Relief of pain

Several techniques may soothe the pain and burning caused by puss moth caterpillar stings.

  • Washing the sting with soap and water and using a hair dryer set on low to dry the area

  • Putting tape on the site and pulling it off to remove embedded hairs to prevent further injury

  • Applying isopropyl alcohol (rubbing alcohol) to the sting

  • Applying a baking soda slurry

  • Applying calamine lotion

  • Placing an ice pack or an ice cube wrapped in plastic and a thin cloth over the sting

More severe reactions require immediate medical attention.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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