Are caterpillars poisonous?
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The bottom line
Some caterpillars have hairs or spines connected to venom glands. When they touch skin, they can cause pain, itching, burning, swelling, and blistering.
Prevention tips
When possible, avoid areas infested with caterpillars.
Teach children to leave caterpillars alone.
Wear a hat and gloves while gardening.
If a caterpillar is on the skin, remove it with a stick or tool. Do not touch it with bare hands.
This really happened
Case 1: A woman brushed her pinky finger against a saddleback caterpillar. She had a lot of redness, blistering, and pain, with a burning sensation that extended into her forearm. She tried ice, baking soda paste, hydrocortisone ointment, other skin creams, and oral antihistamines. Nothing provided relief. Several hours later, she called her poison center and was advised to put some tape onto her finger, sticky side down, then pull up on the tape. She did so and pulled the tiny caterpillar hairs out of her skin. The burning went away soon after, and the pain decreased. She was able to treat the remaining redness and blistering with an ointment containing hydrocortisone and an antibiotic.
Case 2: At school, a teenager put his hand on a stair rail and didn't see a puss caterpillar on it. The sting area was red and painful. The student applied tape to remove the tiny hairs. He washed the area, used hydrocortisone cream on the site, and took diphenhydramine (an antihistamine). His pain and redness went away quickly. By the next day, his hand looked normal.
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What are caterpillars?
A caterpillar is the larval form of a butterfly or moth (Lepidoptera). It develops from a hatched egg. While tiny at first, caterpillars live to eat (in some species, starting with their own eggshells) and quickly grow into the worm-like form we recognize. A caterpillar eventually forms a protective structure (chrysalis or cocoon) around itself in which it dramatically changes its body structure to become an adult butterfly or moth.
Are caterpillars poisonous?
Of the estimated 165,000 Lepidoptera species found worldwide, only about 150 are known to cause serious stings, and only about 50 of these are found in the US.
Unintentional human contact occurs when people brush against caterpillars they don't see. That can easily happen in a yard or garden. It's especially hard for people who work in caterpillar-infested areas to avoid contact.
What to do if you are stung by a caterpillar
If you or someone else is stung by a caterpillar, use the webPOISONCONTROL® online tool to get help, or call your poison center at 1-800-222-1222. Whether online or by phone, expert guidance is always free, confidential, and available 24 hours a day.
Which caterpillars sting in the US?
While most caterpillars are harmless, there are several types of venomous caterpillars in the US that can cause misery to humans who touch them. Among them are the saddleback, io moth, puss moth, spongy moth (formerly called gypsy moth), flannel moth, slug, spiny oak slug, and buck moth caterpillars. To help identify them, see this illustrated guide to stinging caterpillars from the University of Kentucky.
How do caterpillars sting?
Most problems from venomous caterpillar exposures are due to the tiny hairs (setae), spines, or quills on a caterpillar's body. These can be connected to glands that produce a toxin. As part of the caterpillar’s defense strategy, when you touch these stinging hairs or spines, they can break off in your skin, releasing a tiny dose of that toxin in the process. Some cause allergic reactions.
For some caterpillars, their setae can blow on the breeze and land on skin, eyes, and clothing; this is common with spongy moth caterpillars. Occasionally, a young child will do what young children often do: pick up something interesting (the caterpillar) and try to eat it.
Are all fuzzy caterpillars poisonous?
As a general rule, brightly colored caterpillars with spines, bristles, or a fuzzy appearance might be venomous and should not be touched. However, knowing which caterpillars to avoid touching might not be enough to prevent a sting. Preventing venomous caterpillar exposures can be difficult, as they often feed on the underside of leaves and can be hard to see. Wearing a hat and gloves while gardening can help.
What are the symptoms of a caterpillar sting?
Symptoms of caterpillar stings occur when the stinging hairs or spines of a venomous caterpillar contact human skin. Symptoms of exposure to caterpillar venom can include stinging or burning pain, skin redness, itching, swelling, welts, and blisters. Headache and nausea can also occur.
Allergic reactions that involve shortness of breath or difficulty swallowing can develop in some people. Anaphylaxis (a severe, life-threatening allergic reaction) is possible but rare. If someone develops difficulty breathing, fainting, or swelling of the lips, face, or tongue after being stung by a caterpillar, call 911 immediately.
What should you do if a child eats a caterpillar?
A swallowed caterpillar can get stuck and block breathing or swallowing. It might be necessary to physically remove the caterpillar at a hospital. If nothing is blocked, reported cases of children swallowing caterpillars have not led to serious problems.
How to treat a caterpillar sting at home
Pain from a caterpillar sting usually improves within a few hours, but ice and oral pain relievers like ibuprofen or acetaminophen can help. Treatment involves removing the hairs or spines from the skin, then treating the symptoms.
If the caterpillar is on the skin, remove it without using your hands.
Gently put tape over the exposed skin, sticky side down; almost any kind of tape will do. Pull up the tape, removing the embedded hairs or spines. Repeat with fresh pieces of tape as often as needed to treat the area involved.
Wash the area gently with soap and water.
If the area itches, try hydrocortisone cream.
If that doesn't help, try an oral or topical antihistamine like diphenhydramine (Benadryl).
Rinse affected eyes with lukewarm water.
When to see a doctor for a caterpillar sting
Contact your health care provider or go to Urgent Care if you suspect a localized allergic reaction, if the area around the sting is blistered, or if eye irritation persists. Call your health care provider about a tetanus booster if your shots are not up to date.