Definition

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, MOUTH, NOSE AND THROAT

• Drooling
• Pain
• Redness
• Inflamed membranes in the nose
• Increased tears
• Mouth and throat burning and swelling
• Pain
• Redness of the eye

NERVOUS SYSTEM

• Headache

RESPIRATORY SYSTEM

• Cough
• Shortness of breath
• Wheezing

SKIN

• Blisters
• Hives
• Itching
• Rash
• Redness

STOMACH AND INTESTINES

• Vomiting, if caterpillar or caterpillar hairs are eaten

WHOLE BODY

• Pain
• Severe allergic reaction (anaphylaxis). This is rare.
• A combination of symptoms including itching, nausea, headache, fever, vomiting, muscle spasms, tingling in the skin, and swollen glands. This is also rare.

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. Wash the contact area with soap and water, 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 person has blood flow problems, decrease the time ice is used to prevent possible damage to the skin. After several ice treatments, apply a paste of baking soda and water to the area.

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 known
• 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; breathing tube through the mouth and breathing machine in serious allergic reactions
• 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 ECG (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, Marquez A. Arthropod envenomation and parasitism. In: Auerbach PS, Cushing TA, Harris NS, eds. Auerbach's Wilderness Medicine. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 41.

James WD, Elston DM, Treat JR, Rosenbach MA, Neuhaus IM. Parasitic infestations, stings, and bites. 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 20.

Otten EJ. Venomous animal injuries. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. Philadelphia, PA: Elsevier; 2018:chap 55.