The hairs of this particular kind of caterpillar can cause skin rashes and eye or throat irritations. Photo: Wikimedia Commons

Nests of the poisonous oak processionary caterpillar are still being found across Croydon, prompting warnings for residents to steer clear.

The hairs of this particular kind of caterpillar contain a substance that can cause skin rashes and sometimes eye and throat irritations. The nests of these animals may contain thousands of these harmful hairs.

The creatures are also known pests to trees since they eat oak leaves. Oak trees can be eaten bare if there are large numbers of these caterpillars, leaving the tree vulnerable to other threats.

The oak processionary caterpillar got this name because of their habit of moving in nose-to-tail processions. They are the larval stage of oak processionary moth. In June, they usually build their white and silken-webbed nests on the trunks and branches of oak trees. After several days, the nests become discoloured.

Councils and the Forestry Commission are dealing with the problem, and residents are encouraged to help them by reporting sightings of the caterpillars or their nests. Shirley and Ashburton have been singled out in the warning as areas that have already had sightings . However, residents are not advised to handle the problem themselves. Ian Gambles, the Director for England for the Forestry Commission said: “To be as effective and safe as possible, this job needs to be timed just right and done by people with the right training and equipment, and the nests must be disposed of properly.”

For those who have come in contact with a caterpillar and are experiencing any of the described irritations, Dr Deborah Turbitt, the London Deputy Director of Health Protection for Public Health England said: “We advise people to see a pharmacist for relief from milder skin or eye irritations following possible OPM contact, or consult a GP or NHS111 for more-serious reactions. Contact a vet if pets are affected.”