How a caterpillar can hurt you
A stinging caterpillar has no stinger like a wasp. Its hairs or spines break off easily and lodge in the skin, and they are especially irritating if they reach the eyes.
The brown-tail
Brown-tail caterpillars, Euproctis chrysorrhoea, are hairy, with two red bumps towards the rear. Their hairs break off easily and can cause an intense rash.
The rash itches like poison ivy and can last from a few hours to several weeks. It comes from both a chemical toxin in the hairs and the mechanical irritation they cause. You do not even need to touch a caterpillar: the tiny hairs are shed, can drift through the air, and can cause breathing trouble in some people.
The caterpillars spend the winter in dense silk nests at the tips of shoots, which stay visible on bare branches. They start feeding again in April, and where they are numerous their hairs are a risk from April to August. Do not handle the nests or the caterpillars without protection.
Other caterpillars to leave alone
The Io moth caterpillar, Automeris io, carries stinging spines that break off easily and release a painful venom at the slightest touch.
The tiny hairs of spongy moth caterpillars, Lymantria dispar, can cause an itchy red rash in some people, so wear gloves if you have to handle them.
The hickory tussock moth caterpillar, Lophocampa caryae, is fuzzy and white with black tufts. Hairs of tussock moth caterpillars, including the white-marked tussock moth, can cause itching, burning and swelling in some people, and the hairs woven into their cocoons can irritate too.
When to get help
Seek urgent medical help if, after contact with a caterpillar, there are signs of a severe allergic reaction, such as swelling of the lips, mouth or throat, or difficulty breathing or swallowing.
