Oak processionary moth caterpillars can be toxic to humans and animals (Picture: Jam Press/gov.uk)

People have been warned to stay away from a type of toxic caterpillar that has soared in numbers recently.

Oak processionary moth caterpillars can be hazardous to human and animal health.

The insects also feed on the leaves of several species of oak trees which can cause them to lose their leaves and hamper growth.

The were first spotted in the UK in 2006, but according to The Forestry Commission, they’ve spread in numbers across parts of south-east England and are becoming a ‘serious problem’.

Surrey is among the worst hit, it said, due to its many wooded areas.

People are being told to avoid touching the caterpillars and to report sightings.

The pests are grey with blackheads and long white hairs. The hairs contain proteins which can cause itchy rashes and eye and throat irritations.

The insects feed on several types of oak trees before turning into moths (Picture: Jam Press/Henry Kuppin)

They have a dark stripe down their back and can grow up to 2cm in length.

The caterpillars nests are typically dome or teardrop-shaped, averaging the size of a tennis ball.

Anyone who makes contact with the insects should seek a pharmacist.

Last month a deadly Asian hornet was spotted for the second time in the UK this year.

Just one Asian hornet can consume up to 50 honey bees a day, while a swarm of the deadly insects can kill a hive of 30,000.

Also known as Asian predatory wasps, the hornet’s sting is even capable of killing a human.

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The caterpillars are becoming a ‘serious problem’ say experts.