It’s true that an encounter with a caterpillar isn’t as dangerous as, say, a bee sting or a tick bite can be. But caterpillars aren’t always as innocent as they look. Children may find it fun to play with a caterpillar, but it could cause an itchy and even painful rash.
Here’s what to know about how to recognize a rash caused by a caterpillar and what to do if your child gets one.
Caterpillar Rash Causes and Symptoms
The fuzzy tufts on caterpillars are what can cause a rash. These tiny hairs are called setae. In some people, these hairs cause an allergic reaction when they touch the skin.
This immune response occurs when the body sees a substance as a threat even if it’s not. The immune system will flood the body with a chemical called histamine. Touching a caterpillar can trigger this release of histamine, causing redness, swelling, itching, rash, welts, and small, fluid-filled sacs called vesicles. There may also be a burning or stinging sensation.
These symptoms can appear within minutes and last for one or more days.
Incorrect Diagnoses
Rashes from caterpillars can easily be mistaken for something else, and therefore not treated properly. In 2011, 23 children in Florida developed rashes from exposure to white-marked tussock moth caterpillars (Orgyia leucostigma).
According to the report issued by the Centers for Disease Control and Prevention (CDC), most of the kids were diagnosed with other conditions at first. These included chickenpox, molluscum contagiosum, and even potentially life-threatening MRSA infections.
In other cases, rashes caused by caterpillars have been mistaken for flea bites, mosquito bites, scabies, scarlet fever, fifth disease (parvovirus B19), and contact dermatitis.
One of the recommendations by the CDC in response to the Florida outbreak was to advise schools and daycare centers where caterpillars are common to power wash playground equipment to remove the caterpillars.
Treatment
If your child develops a rash after an encounter with a caterpillar, it usually won’t be serious and can be treated at home. If the reaction is mild, you will first need to remove any of the tiny hairs that have rubbed off onto the skin.
To do this, place a strip of tape on the area of skin with the hairs. The hairs will stick to the tape when you pull it off. This works the way a lint roller does (and you can actually use one of those if you have one). Repeat with fresh pieces of tape until you’ve gotten off all the hair that you can.
Then, wash the skin with soap and water and apply a low-strength over-the-counter steroid cream. If the rash really stings, applying ice for 10 to 15 minutes will usually help relieve the pain.
It is extremely unlikely that caterpillar setae could cause anaphylaxis, a full-body, sometimes life-threatening reaction, but it has been seen occasionally after exposure to certain caterpillars.
Summary
Rashes from a caterpillar are rarely serious, but they can be painful. Let your child know that it’s best not to touch them. If they do get a rash, it should go away quickly once the hairs are removed. If your child seems to be having a more serious reaction, call your pediatrician or go to an urgent care center or emergency room.
