Processionary Moth Exposure in Europe: Toxic–Irritant and Immunoglobulin E-Mediated Endotypes, Diagnosis and Management

Abstract

Processionary moths (Thaumetopoea spp.), particularly the oak processionary moth (Thaumetopoea processionea), are an increasingly relevant cause of allergic and toxic disease in Europe, occurring in the context of reported range expansion, changing environmental conditions and persistent contamination with airborne urticating hairs (setae). Clinical manifestations range from toxic–irritant dermatitis and ocular injury to respiratory symptoms, while a subset of exposed individuals develops genuine IgE-mediated disease, including rhinoconjunctivitis, asthma, and rare cases of anaphylaxis. These presentations reflect two mechanistically distinct endotypes: (i) toxin-driven epithelial penetration by the urticating hairs with neuro-inflammatory activation and (ii) allergen-specific sensitisation to defined molecular components such as Tha p 1 and Tha p 2. Accurate endotype differentiation is clinically relevant, as symptom latency, severity, and risk of systemic progression differ substantially. Diagnostic evaluation relies on exposure history and phenotype recognition, complemented in selected cases and experienced centres by skin testing using research-grade extracts and emerging component-resolved approaches. Basophil activation testing may provide additional mechanistic insights in selected cases. Management comprises prompt decontamination, anti-inflammatory therapy, urgent ophthalmologic assessment when eye involvement is suspected, and guideline-based management of anaphylaxis. The environmental persistence of setae and recurrent seasonal exposure highlight the need for improved surveillance, validated molecular diagnostics, and translational research defining immune mechanisms and biomarkers.