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Oak processionary moth: the caterpillar you must not touch

The danger is not the caterpillar itself but its hairs. Each larva carries hundreds of thousands of tiny barbed hairs containing thaumetopoein, and they break off and travel on the wind. Contact causes itching rashes, eye irritation and, in some people, breathing difficulty — without ever touching the animal.

  • 0High risk
  • 6Medium
  • 0Low
  • 6Zones tracked

How to recognise it

Grey-brown caterpillars with long white hairs that move in nose-to-tail processions up and down oak trunks, and build teardrop-shaped silken nests on the trunk and branches. The hairs remain active in old nests and in the leaf litter below for a long time after the caterpillars have gone, which is why cordons stay up around affected trees.

Why it is spreading

The moth has expanded steadily northwards through Europe and is now established in parts of Denmark, the Netherlands, Germany, Belgium and southern England. Municipalities cordon off and professionally remove nests, and those cordons are worth obeying precisely because the hazard is invisible and airborne.

How to avoid it

  • Never touch the caterpillars, the nests, or anything that has been in contact with them.
  • Keep well away from cordoned oaks and do not picnic or sit under an affected tree.
  • Keep children and dogs away; dogs are badly affected by mouth and paw contact.
  • Do not attempt to remove a nest yourself — report it to the local authority.
  • Avoid drying laundry outdoors near infested oaks during the caterpillar season.

If it happens

  • Do not rub or scratch. Remove contaminated clothing carefully and wash it hot and separately.
  • Shower and wash hair to remove hairs from skin.
  • Use an antihistamine for itching and rinse eyes thoroughly with water.
  • Seek medical help for eye involvement, severe rash, or any breathing difficulty.

General guidance only — not a substitute for medical advice or local emergency services.

Where we track it

6 zones in the Dangers Here hazard database, by danger level.

Medium

  • Copenhagen — Artillerivej
  • Herning
  • Kerteminde
  • Morsø
  • Nordfyn
  • Odense

Questions

Where is oak processionary moth a risk?

We track 6 zones for this hazard. 6 are rated medium and 0 low.

How do you avoid oak processionary moth?

Never touch the caterpillars, the nests, or anything that has been in contact with them. Keep well away from cordoned oaks and do not picnic or sit under an affected tree. Keep children and dogs away; dogs are badly affected by mouth and paw contact.

What is the first aid for oak processionary moth?

Do not rub or scratch. Remove contaminated clothing carefully and wash it hot and separately. Shower and wash hair to remove hairs from skin. Use an antihistamine for itching and rinse eyes thoroughly with water.

How to recognise it

Grey-brown caterpillars with long white hairs that move in nose-to-tail processions up and down oak trunks, and build teardrop-shaped silken nests on the trunk and branches. The hairs remain active in old nests and in the leaf litter below for a long time after the caterpillars have gone, which is why cordons stay up around affected trees.

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