To the Editor,
Shrimp allergy is one of the most prevalent food allergies and a major shrimp allergen is the muscle protein tropomyosin (Pen a 1). In a Swedish study of young asthmatics, 15% were sensitized to shrimp and 8% reported symptoms of shrimp hypersensitivity1. House dust mites are one of the most common allergens to which asthmatic patients are sensitized2. Tropomyosin has been identified as an allergen in house dust mites, insects, and molluscs, making it likely that patients sensitized to shrimp and house dust mites are also at risk of cross-reactions to tropomyosin from other species. Allergic reactions mediated by cross-reactive IgE can occur in individuals primarily sensitized to airborne allergens, who also show sensitivity to proteins present in food. It has been shown that IgE from shrimp allergic patients can recognize proteins from insect extracts3.
In this study, we assessed the prevalence of shrimp and house dust mite sensitization in a large population-based study and compared IgE sensitization in relation to allergic disorders and respiratory symptoms. Chi-squared test and ANOVA was used to detect group differences in univariate analyses, while logistic and linear regression was used in adjusted analyses.
A total of 4593 randomly selected adult subjects aged 50-64 years from the Swedish CArdioPulmonary bioImage Study (SCAPIS, Uppsala cohort) took part in an extensive questionnaire, blood sampling, physical examinations, lung function tests, and imaging4,5. IgE sensitization was defined as having specific IgE ≥0.35 kUA/L, measured by ImmunoCAP (Thermo Fisher Scientific, Uppsala, Sweden). Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) after bronchodilation were measured. Chronic airflow limitation (CAL) was defined as having FEV1/FVC ratio <0.70.
Of all participants, 253 (5.5%) were IgE-sensitized to shrimp (≥0.35 kUA/L), 191 (4.2%) to mites, and 104 (2.3%) to both allergens. Of the shrimp-sensitized patients, 41% were also sensitized to mites, while 54% of the mite-sensitized patients were also sensitized to shrimp.
Participants with complete IgE results (n=4593) were divided into four groups based on sensitization to shrimp, house dust mites, both shrimp and house dust mites, or neither allergen (see Table 1 for details). Significant group differences were found regarding prevalence of asthma, allergic rhinitis, urticaria, angioedema, wheeze, FEV1and CAL.
Table 1. Characteristics of study groups defined by sensitization to shrimp and/or house dust mite (% and mean±SD)