How to Spot and Treat a Caterpillar Rash
Medically reviewed by Corinne Savides Happel, MD
A rash from a caterpillar, also called lepidopterism, occurs when the tiny hairs on a caterpillar touch the skin and cause a rash.
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 can cause a red, itchy, swollen, and even painful rash. Treatment for caterpillar rash may include ice packs, antihistamines, steroid cream, and more.
Here's what to know about how to recognize a rash from a caterpillar, what symptoms you may experience, and how to treat it.
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 symptoms such as:
Redness
Swelling
Itching
Rash
Welts
Vesicles (small, fluid-filled sacs)
Burning or stinging sensation
These symptoms can appear within minutes and last for one or more days.
Takeaway
Sometimes you can get a rash without actually putting your fingers on a caterpillar. The little tufts can become airborne and land on bare skin. Caterpillars can also leave setae behind on items like trees or playground equipment. This is more likely when there are a lot of caterpillars in one area.
If you touch your eyes or nose after handling a caterpillar (or if a child places one in their mouth), there could be a more serious reaction. Symptoms might include
Sneezing
Coughing
Runny nose
Red eyes
Shortness of breath
Mouth pain
Itching
Difficulty swallowing
If you notice any of these symptoms, go to your nearest urgent care center or emergency room.
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. Seek immediate emergency care with symptoms such as:
Hives
Significant swelling of the tongue or lips
Difficulty breathing or swallowing
Nausea, vomiting, or diarrhea
Headache, sweating, or dizziness
Related: Allergic Reactions to Insect Bites and Stings
Diagnosis
There are no tests to make a diagnosis, so a healthcare provider will perform a physical exam and ask about your symptoms.
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:
Scarlet fever
Flea bites or mosquito bites
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.
How Do You Treat a Caterpillar Rash?
If a rash develops 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 caterpillar hairs on the skin.
To do this, place a strip of tape on the area of the 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 removed most or all of the caterpillar hairs.
Then, wash the skin with soap and water and use any additional treatment options, such as:
Ice pack applied to the area for 10 to 15 minutes
Baking soda mixed with a small amount of water to make a paste
Over-the-counter non-drowsy oral antihistamine (such as Zyrtec or Clarinex)
Over-the-counter corticosteroid creams
How to Prevent Caterpillar Rash
There are several ways to prevent caterpillar rash, including:
Avoid touching all caterpillars.
Learn how to identify harmful types and avoid touching them.
Find out where caterpillars are most common in your local area, when their in peak season, and then avoid the area during that time.
Wear protective clothing, including a long-sleeved shirt, pants, long socks, and closed-toed shoes.
Summary
Rashes from a caterpillar are rarely serious, but they can be painful. If you do get a rash, it should go away quickly once the hairs are removed and you treat it with at-home and over-the-counter remedies. If you have a more serious reaction, call your healthcare provider or go to an urgent care center or emergency room.
Related: When to See a Doctor About a Skin Rash
Read the original article on Verywell Health.
