Rash on the skin of a 28 year old male patient exposed to the oak processionary moth caterpillars (Thaumetopoea processionea). The hairs (setae) that cover the caterpillar are poisonous and can cause skin irritation (caterpillar dermatitis) and respiratory problems, including asthma. Even if the larvae are not handled, the setae can break off, becoming airborne. Treatment is with antihistamines.