Dog lying in grassland

Danger from Oak Processionary Moth

Guide for dog owners: How to protect your dog from the poisonous caterpillar 


The health risk for dogs comes from the caterpillars of the oak processionary moth. The most dangerous part of these caterpillars is their hair. The thousands of urticating hairs contain thaumetopoein, an irritant substance, which can become a serious problem for other animals. The greatest risk period is from May to July when the caterpillars come down from the trees to become adult moths on the ground.

The oak processionary moth (Thaumetopoea processionea) is a relatively small moth. The caterpillars mainly live on oak trees but also like to colonise other tree species in parks and forests and often appear in larger groups. In stressful situations or threats, the oak processionary moth sheds its hair. Each hair has a hook that sticks in the dog's skin. As a result, the hair breaks and releases its irritating substance. The caterpillar hairs last for many years and are therefore a danger in the areas where they settle.

How do you recognise the dangerous caterpillars?

Identifying caterpillars and nests is important to be able to react in time to protect your dog.

The caterpillars have black heads and bodies covered with long white hairs which contain the problematic substance. The nests are usually dome-shaped or drop-shaped with a diameter similar to that of a tennis ball. Initially, the nests are white, but with time they change colour and take on a brown colour.

Oak Processionary Moth on ground

What happens, if your dog is in contact with the caterpillar?

If the dog comes in contact with the caterpillar or its nests and the hairs get into the nose/mouth, reactions such as drooling, swelling of the tongue, inflammation of the conjunctiva, vomiting, breathing difficulties and swollen mouth may occur.

If the hair gets into the lungs, various lung problems can occur. If the hair gets into the digestive tract by swallowing, damage can also occur there.

Swelling of the tongue and the mucous membranes in the throat can cause danger of suffocation.

In any case, an affected dog must be given veterinarian attention, as the consequences are sometimes severe and fatal.

see a veterinarian

If the tongue and mucous membranes in the throat swell, there is a risk of suffocation. In any case, the affected dog needs medical attention, as the consequences can be serious.

How to protect the dog?

In the best case:

  • Avoid areas where there is an increased incidence of the oak processionary moth.
  • Dog owners should pay attention to warnings. These are issued by the responsible authorities in case of severe infestation.
  • When travelling in an affected area, your dog must be kept on a leash to avoid stumbling across the caterpillar.
  • Familiarise yourself with the appearance of the caterpillar and nests in order to identify them.
  • Call your dog from the caterpillars/nests in time.


Every season has its own dangers. Dog owners do well to deal with them and be prepared accordingly. The dog can be protected from unnecessary health problems. 


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