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)