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Caterpillars

Caterpillars are the larvae (immature forms) of butterflies and moths. There are many thousands of types, with a huge variety of colors and sizes. They look like worms and are covered in small hairs. Most are harmless, but some can cause allergic reactions, especially if your eyes, skin, or lungs come in contact with their hairs, or if you eat them.

This article is for information only. DO NOT use it to treat or manage symptoms from exposure to caterpillars. If you or someone you are with is exposed, call your local emergency number (such as 911), or your local poison center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States.

Symptoms

Below are symptoms of exposure to caterpillar hairs in different parts of the body.

Eyes

  • Pain
  • Redness
  • Increased tears

Stomach and intestines

  • Drooling
  • Mouth and throat irritation
  • Vomiting, if caterpillar or caterpillar hairs are eaten

Nervous system

  • Headache

Respiratory system

  • Cough
  • Inflamed membranes in the nose
  • Shortness of breath
  • Wheezing

Skin

  • Blisters
  • Hives
  • Itching
  • Rash
  • Redness

Whole body

  • Pain
  • Severe allergic reaction (anaphylaxis is rare)
  • Swelling

Home Care

Remove irritating caterpillar hairs. If the caterpillar was on your skin, put sticky tape (such as duct or masking tape) where the hairs are, then pull it off. Repeat until all hairs are removed. Put calamine lotion on the affected area, and then ice. Place the ice (wrapped in a clean cloth) on the affected area for 10 minutes and then off for 10 minutes. Repeat this process. If the patient has blood flow problems, decrease the time ice is used to prevent possible damage to the skin.

If the caterpillar touched your eyes, flush your eyes right away with plenty of water, and then get medical help.

Get medical care if you breathe in caterpillar hairs.

Before Calling Emergency

Have this information ready:

  • Person's age, weight, and condition
  • Type of caterpillar, if possible
  • Time of the incident

Poison Control

Your local poison center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States. They will give you further instructions.

This is a free and confidential service. All local poison control centers in the United States use this national number. You should call if you have any questions about poisoning or poison prevention. It does NOT need to be an emergency. You can call for any reason, 24 hours a day, 7 days a week.

What to Expect at the Emergency Room

Bring the caterpillar to the hospital, if possible. Make sure it is in a secure container.

The health care provider will measure and monitor your vital signs, including temperature, pulse, breathing rate, and blood pressure. Symptoms will be treated. You may receive:

  • Blood and urine tests
  • Breathing support, including oxygen
  • Eye examination and numbing eye drops
  • Eye flushing with water or saline
  • Medicines to control pain, itching, and allergic reactions
  • Skin examination to remove all caterpillar hairs

In more serious reactions, intravenous fluids (fluids through a vein), x-rays, and EKG (electrocardiogram or heart tracing) may be necessary.

Outlook (Prognosis)

The faster you get medical help, the faster your symptoms will go away. Most people do not have lasting problems from exposure to caterpillars.

References

Erickson, TB, Márquez A, Jr. Arthropod envenomation and parasitism. In: Auerbach PS, ed. Wilderness Medicine. 6th ed. Philadelphia, PA: Elsevier Mosby; 2011:chap 50.

James WD, Berger TG, Elston DM. Parasitic infestations, stings, and bites. In: James WD, Berger TG, Elston DM, eds. Andrews' Diseases of the Skin: Clinical Dermatology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 20.

Steen CJ, Schwartz RA. Arthropod bites and stings. In: Wolff K, Goldsmith LA, Katz SI, et al., eds. Fitzpatrick's Dermatology in General Medicine. 7th ed. New York, NY: McGraw-Hill; 2008:chap 210.

Update Date 7/14/2015

Updated by: Jacob L. Heller, MD, MHA, Emergency Medicine, Virginia Mason Medical Center, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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