Poisonous caterpillars are on the rise in a number of areas in south London.
People are being reminded not to touch caterpillars of the oak processionary moth (OPM) which are beginning to emerge in oak trees.
They are also advised to keep children, pets and livestock away from the caterpillars and their nests, which cause health problems.
Residents are also being told to report any sightings of these little critters.
Boroughs in south London including Croydon, Bromley and Elmbridge are said to be affected.
OPM caterpillars are a tree pest which were accidentally introduced to Britain.
They feed on oak leaves and in large numbers they can severely defoliate trees and leave them vulnerable to others pests and diseases.
Their tiny hairs contain a protein which can cause itchy skin rashes, eye and throat irritations and, occasionally, breathing difficulties, in people and animals.
The hairs can be blown on the wind, and left in their nests in and under oak trees. The greatest risk period is May to July, although nests should not be approached at any time.
Dr Yvonne Doyle, London Regional Director of Public Health England, said: “We strongly advise people not to touch or approach the caterpillars or their nests because of the health risks posed by the toxin-containing hairs.
“Pets can also be affected, and should be kept away as well. If you would like to know what these caterpillars look like, please see the Forestry Commission’s website for pictures.
“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.
“We have issued advice to local GPs and health professionals to help them identify when patients have been affected by the caterpillars and to advise them on appropriate treatment.”
Further information is available from www.forestry.gov.uk/opm.