Over the past few weeks, the poisonous oak processionary caterpillars have been sighted throughout Luxembourg again. The caterpillars can cause allergic reactions and irritation if humans come into contact with them.

At the end of May, the Luxembourg City municipal authorities published a warning concerning the caterpillars, as they had been sighted in Cents, Hamm, Bonnevoie, and Kirchberg.

Although the caterpillars received a lot of coverage in the media last year, that was not the first time that oak processionary caterpillars have been a public health issue. The caterpillars have been around for longer and can usually be found, as the name might suggest, on oak trees. The caterpillars can cause health issues in humans and animals.

Older caterpillars are covered in bristles, which pose the main danger to humans and animals. The bristles contain a specific toxin which can cause allergic reactions. The reaction mainly manifests as a rash, but can also cause respiratory issues including asthma and lead to conjunctivitis.

Anybody who comes into contact with the caterpillar's bristles should immediately wash them off or shower if possible.

The authorities also advise washing clothes. If someone experiences a stronger reaction to coming into contact with the bristles, they should go to the doctor.

The Ministry of the Environment has republished a flyer containing the above information on the risks of oak processionary caterpillars as well as guidance on what to do if one has come into contact with a caterpillar.

The flyer was created in 2017 as a collaborative effort between the Ministry of Health and the then-Ministry of Sustainable Development and Infrastructure. The flyer is available in German.