Non-occupational allergy caused by the Pine Processionary Caterpillar (Thaumetopoea pityocampa)

Contact w ith the pine processionary caterpillar induces dermatitis, usually located in exposed areas, and, less frequently, ocular lesions through a toxic-irritative mechanism. Recently, the existence of an immediate hypersensitivity mechanism has been demonstrated, mainly in occupationally exposed patients. Objective: To present four patients who experienced allergic reactions (urticaria-angioedema and rhinitis-asthma) after non-occupational exposure to pine processionary caterpillar. Patients and methods: The four patients underwent allergy testing through skin prick tests (SPT), specific IgE detection and SDS-PAGE immunoblotting. One patient also underwent a specific bronchial challenge test w ith the pine processionary antigen. Results: In all patients, both SPT w ith the caterpillar extract and specific IgE were positive. Western blotting showed several IgE-binding bands w ith molecular mass values ranging from 18 to 107 kDa. A shift in the electrophoretic mobility of some of the relevant allergens occurred under the presence of a reductive agent ( -mercaptoethanol). The specific bronchial challenge test w ith pine processionary antigen performed in one of the patients also produced positive results. Conclusions: The results of this study show an immunologic IgE-mediated immediate hypersensitivity mechanism in these reactions. The processionary caterpillar’s airborne urticating hairs or spicules should be considered, at least in some locations, not only as contact and occupational allergens, but also as seasonal aeroallergens.