Puss Moth Caterpillar Stings

(Asp Stings)

ByRobert A. Barish, MD, MBA, University of Illinois at Chicago;
Thomas Arnold, MD, Department of Emergency Medicine, LSU Health Sciences Center Shreveport
Reviewed/Revised Jun 2022 | Modified Sept 2022
VIEW PROFESSIONAL VERSION

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.

(See also Introduction to Bites and Stings.)

Treatment of Puss Moth Caterpillar Stings

  • 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.

quizzes_lightbulb_red
Test your KnowledgeTake a Quiz!
Download the free Merck Manual App iOS ANDROID
Download the free Merck Manual App iOS ANDROID
Download the free Merck Manual App iOS ANDROID