Allergy to the pine processionary caterpillar (Thaumetopoea pityocampa)

Background The contact with the pine processionary caterpillar (Thaumetopoea pityocampa) induces dermatitis and ocular lesions by a mechanic and toxic mechanism. However, IgE-mediated hypersensitivity to this caterpillar has been demonstrated in two recent studies. Objective To find if an IgE-mediated mechanism was operative among patients with suspected previous reactions to processionary caterpillars, particularly exposed workers. Methods Fifty-five patients were studied by skin prick test (SPT), and specific IgE detection by immunoblotting. Results A total of 58.18% patients had a positive SPT for caterpillar extract. Positive SPT patients had more generalized cutaneous reactions (47%) and oedema (50%) as well as a shorter latency period (mean, 36 min) and duration of cutaneous lesions (mean, 26 h) than the patients with negative SPT. A total of 60% of the positive SPT patients had occupational exposure to the processionary caterpillar. The occupationally exposed workers showed significant symptoms from October to December. The anaphylactic reactions only appeared in allergic patients with occupational exposure and were also more frequent from October to December. These patients with anaphylactic reactions had a major size of SPT and the exercise was found in them to be a variable that increased the symptoms. The IgE immunoblot detected in the caterpillar extract several reactive bands with apparent molecular weights from to 35-4 kDa in 72% of the cases with positive SPT . Conclusions Allergic reactions to T. pityocampa urticating hairs have different clinical characteristics than those induced by a toxic-irritative mechanism and are more frequent than suspected. Allergic reactions to this caterpillar among occasional visitors to pine-wood areas, and particularly in pine-forest workers, should be taken into consideration by allergists.