Anisakis simplex as a risk factor for relapsing acute urticaria: a case-control study

IgE-mediated hypersensitivity reactions to Anisakis simplex have been described after ingestion of fish, suggesting that sensitisation to this parasite may induce acute urticaria and anaphylaxis. Anisakis simplex allergens are highly resistant to heat and freezing, and sensitisation may occur even in populations with low consumption of raw/undercooked fish. This study aimed to quantify the association between sensitisation to A. simplex and relapsing acute urticaria.

This is the first case-control study on this topic. Cases (n = 200) were patients with a clinical diagnosis of relapsing acute urticaria, consecutively approached at the immunoallergology unit of Porto's largest paediatric hospital. Controls (n = 200) were consecutively selected at the surgery department of the same hospital, from subjects undergoing programmed orthopaedic, maxillofacial or general surgical procedures. Specific IgE measurements (Anisakis and Ascaris) were taken, and skin-prick tests (A simplex, common aeroallergens, fish, and Ascaris) were done.

Sensitisation to A simplex (OR 3.86, 95% CI 2.04% to 7.29%), Ascaris (OR 3.37, 95% CI 1.89% to 6.02%), fish (OR 4.62, 95% CI 1.85% to 11.52%), and at least one aeroallergen (OR 4.59, 95% CI 2.99% to 7.05%) were associated with increased risk of acute urticaria. Regarding the sensitisation to A simplex, the aeroallergen sensitisation-adjusted OR was 2.61 (95% CI 1.33% to 5.12%) for the whole sample, and 2.72 (95% CI 0.99% to 7.47%) for those not sensitised to Ascaris or fish.

Sensitisation to A simplex increases the risk of relapsing acute urticaria in subjects not sensitised to Ascaris or fish, and this is independent of aeroallergen sensitisation.