Challenge-verified shrimp allergy in a Danish patient cohort throughout 23 years.

Background Shrimp allergy is a prevalent, although data from Northern Europe are limited. This study evaluated oral food challenge (OFC)-verified shrimp allergy and the relationship between shrimp and house dust mite (HDM)-sensitizations in patients suspected of shrimp allergy. Methods Patients undergoing OFC to shrimp between 2002 and 2024 were retrospectively included (n=324). Clinical OFC data, skin prick-prick tests (SPT), serum-specific immunoglobulin E (s-IgE) to shrimp and HDM (Dermatophagoides pteronyssinus, Dermatophagoides farinae), and demographics were analyzed. Risk factors for positive OFC were evaluated using multivariate logistic regression. Results Shrimp allergy (all shrimp-types) was confirmed by OFC in 12.3% (n=40), with a higher prevalence in children/adolescents (≤17 years) than in adults (22.8% vs 8.2%, p<0.001). The median cumulative eliciting dose was 18.8 grams (interquartile range: 8.8-48.8). Reactions were predominantly cutaneous, mucosal, and gastrointestinal; 10% developed anaphylaxis. Patients allergic to Northern Shrimp (positive OFC) more frequently had positive SPT to shrimp (23.7% vs 4.7%, p<0.001) and trended toward higher shrimp-specific s-IgE. Sensitization to HDM was more frequent in shrimp-allergic than tolerant patients (68.6% vs 46.6%, p=0.013). A stronger response to shrimp than HDM (difference in SPT >1 mm or s-IgE >1 kUA/L) was associated with positive OFC. Mono-sensitization to shrimp (odds ratio (OR)=6.41), concomitant shrimp and HDM sensitization (OR=8.89), and age ≤17 years (OR=0.27) were independent risk factors for a positive OFC. Conclusion Shrimp allergy was confirmed by OFC in 12% of suspected cases evaluated at a tertiary allergy centre. Cross-reactivity with HDM may impair the diagnostic accuracy of conventional allergy tests, highlighting the need for improved in vitro-diagnostics.