Hairy caterpillars (Oak processionary moth)

What do they look like?

These caterpillars walk up and down trees in nose-to-tail processions.

If you find them, or spot one of their white silken nests, report it to the Forestry Commission or to your local council. The caterpillars of the oak processionary moth are classified as a public health hazard and the authorities destroy their nests whenever they are reported.

Why are they dangerous?

These oak processionary moth caterpillars are an invasive speciaes which is not native to Britain. They were first found in the UK in 2006 and are now a recurrent problem in London and parts of southeast England. They are not just a health hazard for humans and our pets, but a threat to native species of plants and animals. 

In late spring and summer, the caterpillars have thousands of tiny hairs that can cause itchy rashes, eye problems, sore throats – and very occasionally breathing difficulties. The hairs can become detached from the caterpillars and be spread by the wind. The hairs will remain on trees after the caterpillars have moved on. The caterpillars feed on leaves and seriously damage trees, making them liable to other parasites and susceptible to blow down in strong winds. 

If you see a caterpillar on your skin and try to brush it off, it will release its harmful hairs as a defence mechanism.

How can I avoid them?

Do not touch any caterpillars! You can watch them without disturbing them, but please report them to the authorities for the sake of the environment.

The caterpillars are at their most dangerous in May, just before they transform into moths. 

DID YOU KNOW? Oak processionary moth eggs were introduced to Britan on trees imported from Europe. They are most heavily concentrated in and around London, where thousands of nests have been removed. 

What to do if I come into contact with them?

If a caterpillar of the oak processionary moth gets on your skin:

  • Use tweezers or a pen to remove it.
  • Try not to disturb it (for example, by brushing it off with your hands) as it will then release more hairs.
  • Rinse your skin with running water, allow it to air dry and then use sticky tape to strip off any leftover hairs.
  • DO NOT towel dry yourself after rinsing.
  • Use calamine lotion, ice packs or a pharmacy remedy containing 3.5% ammonia to relieve the itch.
  • DO NOT use cream containing antihistamine.
  • Remove all contaminated clothes and wash at the highest temperature the fabric allows.


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