After causing havoc in neighbouring countries in the past, there are signs that a poisonous little critter is making itself known in Switzerland too. Following an incident where 13 children were admitted to hospital for allergic reactions, experts have warned the public to avoid touching oak processionary moth caterpillars. 

13 children admitted to Basel hospital with allergic reactions

On Tuesday, 13 children on a school trip in Rünenberg, Canton Basel-Land were all admitted to hospital for allergic reactions, Swiss police confirmed. The patients, who complained of skin and eye irritations and breathing difficulties, were treated by paramedics before 10 were taken to the hospital and three were airlifted for further examination.

Luckily, police spokesperson Adrian Gaugler told Blick that all the children were able to return home to their families. Now, with Gaugler confirming that the teachers are not suspects in the case, experts turned their attention to what could have caused such a sudden bout of allergic reactions.

Oak processionary moth caterpillar blamed for hospital admissions in Switzerland

Suspicions were confirmed later when the authorities announced the oak processionary moth caterpillar was likely to blame. While they may look cute, the 600.000 long hairs covering the creature's body contain an irritating toxin called thaumetopoein that can cause itchy, blistering rashes, sometimes lasting for weeks at a time. 

In extreme cases, the hairs can also cause more severe allergic reactions such as breathing difficulties. What’s more, you don’t have to stroke the caterpillar to get the itch - gusts of wind are known to spread the stinging hairs hundreds of metres from the caterpillar itself. In the past, this phenomenon has led authorities to close schools, lakes and other swimming areas, the most notable examples being in Germany and the Netherlands in 2019.

What you need to know about Switzerland's poisonous caterpillar

The caterpillars are at their most potent from May and June until when they turn into moths around July and August. During this time, they are typically seen in lines of 20 to 30 caterpillars, hence the name processionary.

In a statement given to 20 Minuten, Tox Info Switzerland warned against encountering oak processionary moth caterpillars, and advised the public to take the following steps:

• Avoid affected areas: local councils often close off areas where oak processionaries are spotted, but oaks with bare branches or with white-grey webs are also signs that they are present.
• Heed warning signs issued by the local authorities.
• Keep your distance from caterpillar nests, even abandoned ones as they will still contain hairs.
• Never touch a hairy caterpillar.
• Wear long clothing in affected areas.

If you are unlucky enough to be caught by the hairs, officials recommend the following:

• Do not run your hands through your hair or rub your eyes.
• Do not try to wipe off the hairs as their barbs stick to the skin, try using an adhesive strip or tape.
• If a hair gets in your eye, rinse with water.
• Change clothes as quickly as possible, ideally outside your home.
• Once you get home shower thoroughly and wash your hair.
• Wash all clothes with hairs at the highest temperature possible for the garment, shoes should be scrubbed while wet.

While lotions and oils can be used to ease the irritation caused by the hairs, if you experience a shortness of breath, skin rash or any other form of severe allergic reaction after coming into contact with the caterpillar, please visit a doctor.