Toxic Caterpillars Prevention: How To Identify Oak Processionary Moths

Toxic caterpillars, which can cause asthma attacks, vomiting and skin rashes, have been spotted southeast of England and in London. Health officials issued warnings letting residents know of the outbreak.

According to British forestry officials, the long white hair of the caterpillars can trigger allergic reactions in humans leading to skin and eye irritation, difficulty in breathing and even anaphylactic shock, the New York Times reported Friday.

The biggest infestation of the Oak Processionary Moths (OPM), which are in their larval stage, were recorded in Greater London, stemming from Kingston upon Thames to Brent. Some infestations were also spotted in Bracknell Forest, Slough and Guildford. The infestation could potentially spread throughout the country but there has been no confirmation about the spread so far, the Times reported.

“At best, you can get contact dermatitis. At worst, you can die,” said Jason J. Dombroskie, manager of the Cornell University Insect Collection and coordinator of the Insect Diagnostic Lab in Ithaca, New York. “You can go into anaphylactic shock and have your airways close up. The airborne hairs set up a whole different ballgame.”​

Talking about the spread of the harm on humans after touching the toxic caterpillars, Dr. Robert Glatter, an emergency doctor at Lenox Hill Hospital in Manhattan, said its reaction is typically slower than that of a bee sting. Glatter also reportedly said that each caterpillar has more than 62,000 toxic strands of hair, each of which when falls to the ground can be active for up to five years.

“This is where the true toxicity of the caterpillar arises,” he said, adding, “Word to the wise — it’s best to observe their beauty from a distance.”

A spokeswoman for Britain’s Department for Environment, Food and Rural Affairs warned people must not "pick up the caterpillar or pick up the nest.”

So far, there have been no reports of serious illness resulting from contact with the caterpillar.

How to identify OPM:

1. These move in nose-to-tail processions

2. They often form an arrow-headed procession

3. These toxic caterpillars are most likely to be found in oak trees

4. Sometimes they can also be found on the ground under oak trees

5. They are largely seen in late spring and early summer

6. They have distinctive long, white hair

7. Unlikely to live on fences, walls and similar structures

Prevention, courtesy Forestry Commission:

1. If spotted, do not touch them

2. Do not approach nests or caterpillars

3. Advise children to stay away from the caterpillars or the nest

4. Animals also must not touch or approach nests or caterpillars

5. Do not try removing nests or caterpillars