A disturbing picture has shown the dangerous impacts which toxic caterpillars , which have been spotted across west London, can have on our beloved pets.

A dog in Frensham had its snout covered in blisters after coming into contact with an oak processionary moth (OPM) nest a few years back.

The owner of Benson posted the shocking photo online after a recent outbreak of the toxic caterpillars in London was reported earlier this month.

According to the Forestry Commission, the larvae of the OPM can cause asthma attacks, vomiting and skin rashes to people and pets who come into contact with them.

Health officials started to treat trees affected by the toxic caterpillar outbreak from Monday April 23, after the caterpillars were spotted emerging from egg plaques.

Speaking to Get Surrey , Benson's owner said that it took weeks for his Jack Russell cross to completely recover after coming into contact with the caterpillars.

He said: "He was taken for a walk on Frensham Common and he sniffed a strange nest that we now identify as OPMs.

"Within six hours, parts of his ears, eyes and nose started to swell up and he was immediately taken to the vet.

"He was medicated and it took two weeks to recover and then another couple of weeks of keeping it clean and removing dead skin."

Picture of dog who sniffed oak processionary moth nest on Frensham Common - Credit @CampervanPup

The larvae are armed with fine hairs which have the ability to cause fevers and throat irritations, according to the Forestry Commission.

Sightings of OPM caterpillars have been reported in large numbers across London and the south-east and people have been urged to avoid coming into direct contact with the species.

The biggest infestations of OPM were recorded in Greater London, with Brent , Ealing , Hounslow , Richmond and Hammersmith & Fulham all affected.

Health precautions

People in the affected areas can take these precautions to minimise the health risks.

  • Do not touch or approach nests or caterpillars
  • Do not let children touch or approach nests or caterpillars
  • Do not let animals touch or approach nests or caterpillars
  • Do not try removing nests or caterpillars yourself
Benson sniffed an oak processionary moth nest on Frensham Common

How to identify the caterpillars

A health official from the Forestry Commission said the caterpillars are known to:

  • Move about in nose to tail processions
  • Often form arrow-headed processions, with one leader and subsequent rows containing several caterpillars abreast
  • Are most likely to be found in oak trees, and sometimes on the ground under oak trees
  • Are most likely to be seen in late spring and early summer
  • Have very long, white hairs which contrast markedly with other, shorter hairs
  • Do not live on fences, walls and similar structures, as some caterpillar species do

For more information on the outbreak, click here .