A toxic breed of caterpillars have been found in the Greater London area.

Residents of London have been warned by the Forestry Commission to avoid a toxic breed of caterpillars that have been found to cause severe health damage.

The hairs of oak processionary moths (OPM) can cause asthma attacks, vomiting, skin and eye irritations, sore throats, skin rashes, and in rare cases, death, and have been spotted in the larva stage across south-east England and London. Officials from the Forestry Commission have warned residents not to touch the caterpillars, and to avoid all contact. Each caterpillar carries approximately 62,000 toxic hairs that can remain active for up to five years once shed. The hairs contain a toxic protein called thaumetopoein, which can be shed by the caterpillar if they feel threatened. Direct contact with the caterpillar, or with just the caterpillar hair, can lead to serious illness in humans and animals.


A gardener described her injuries to the BBC after unknowingly coming into contact with an oak tree that was infested with OPM.

"My first symptom was a rash on my tummy. I was unaware of what is was and thought at first it was a heat rash," she said.

"During this time I had spells of feeling violently sick. I thought I might have shingles.

"The rash got worse and the left side of my face became covered in this sore irritating rash. My left eye became very sore and weepy.

A spokesperson from the Forestry Commission assured residents that officials are taking steps to manage the outbreak, and has been treating infested trees.

"The treatment programme is expected to continue until late May or early June," a spokesman said.

"After that the caterpillars will be too large to be affected by our preferred treatment product."

When the larva is hatched, the caterpillars are orange in colour with a black head. As they age, they appear white in colour and are entirely covered in long white hairs on their body. A long black stripe across their back can be used as a distinguishing feature compared to other similar looking caterpillars that are harmless. OPM also feed in groups, and most often feed on oak trees. They often move in a procession, or form clusters in silk nests, also found generally on oak trees. At the moth stage, they tend to live only a couple of days.

While it is unclear how OPM made the way to Britain, they are believed to have been accidentally transferred as eggs on live oak imports from the Netherlands in 2000. The population spread to Western London, and some parts of Surrey, Middlesex and Berkshire, in part due to warmer temperatures across the capital.

Officials are asking the public to remain vigilant in the summer, particularly when in areas with oak trees, for the safety of their families and their pets. Residents are advised to avoid approaching or trying to remove any nests by themselves. If any suspicious nests are found, they should be reported to the Forestry Commission for the safe removal.