Fish Allergy Around the World—Precise Diagnosis to Facilitate Patient Management

The accurate and precise diagnosis of IgE-mediated fish allergy is one of the biggest challenges in allergy diagnostics. A wide range of fish species that belong to evolutionary distant classes are consumed globally. Moreover, each fish species may contain multiple isoforms of a given allergen that often differ in their allergenicity. Recent studies indicated that the cross-reactivity between different fish species is limited in some cases and depends on the evolutionary conservation of the involved allergens. Fish allergens belong to several protein families with different levels of stability to food processing. Additionally, different preparation methods may contribute to specific sensitization patterns to specific fish species and allergens in different geographic regions. Here, we review the challenges and opportunities for improved diagnostic approaches to fish allergy. Current diagnostic shortcomings include the absence of important region-specific fish species in commercial in vitro and in vivo tests as well as the lack of their standardization as has been recently demonstrated for skin prick test solutions. These diagnostic shortcomings may compromise patients' safety by missing some of the relevant species and yielding false negative test results. In contrast, the avoidance of all fish as a common management approach is usually not necessary as many patients may be only sensitized to specific species and allergens. Although food challenges remain the gold standard, other diagnostic approaches are investigated such as the basophil activation test. In the context of molecular allergy diagnosis, we discuss the usefulness of single allergens and raw and heated fish extracts. Recent developments such as allergen microarrays offer the possibility to simultaneously quantify serum IgE specific to multiple allergens and allergen sources. Such multiplex platforms may be used in the future to design diagnostic allergen panels covering evolutionary distant fish species and allergens relevant for particular geographic regions.

Fish allergy tolerance 16 months after diagnosis

Fish allergy is generally thought to be persistent, and approximately 80% of patients with fish allergies do not develop tolerance even 10 years after diagnosis. There have been no reports of rapid tolerance development in patients with severe fish allergies. We report the development of tolerance 16 months after the diagnosis of fish allergies. A 13-month-old boywas diagnosed with rosefish allergy (Sebastes matsubarae) and Japanese jack mackerel allergy (Trachurus japonicus). To find out which species of fish he could consume safely, he underwentseveral oral food challenge (OFC) tests. It was determined that he could consume tuna, salmon, cod, sardine, chub mackerel (Scomber japonicus), and Japanese amberjack (Seriola quinqueradiata) without eliciting signs of allergy. He continued to eat the fish that did not produce allergic reactions three to four times a week. The titer of serum allergen-specific immunoglobulin E (IgE) to fish had decreased in a subsequent ImmunoCAP®-specific IgE bloodtest performed 16 months after the diagnosis of the rosefish allergy. Following this test result, he underwent OFCs with rosefish and Japanese jack mackerel, both of which turned out to be negative, and it was determined that he had developed tolerance to fish. In this case, the repeated OFCs were useful in identifying fish species that were safe for consumption. In addition, the decrease in allergen-specific IgE was useful in predicting the development of tolerance. We hypothesize that proactive consumption of available fish species may lead to this rapid induction of tolerance to fish allergens

Effect of Processing on Fish Protein Antigenicity and Allergenicity

Fish allergy is a life-long food allergy whose prevalence is affected by many demographic factors. Currently, there is no cure for fish allergy, which can only be managed by strict avoidance of fish in the diet. According to the WHO/IUIS Allergen Nomenclature Sub-Committee, 12 fish proteins are recognized as allergens. Different processing (thermal and non-thermal) techniques are applied to fish and fishery products to reduce microorganisms, extend shelf life, and alter organoleptic/nutritional properties. In this concise review, the development of a consistent terminology for studying food protein immunogenicity, antigenicity, and allergenicity is proposed. It also summarizes that food processing may lead to a decrease, no change, or even increase in fish antigenicity and allergenicity due to the change of protein solubility, protein denaturation, and the modification of linear or conformational epitopes. Recent studies investigated the effect of processing on fish antigenicity/allergenicity and were mainly conducted on commonly consumed fish species and major fish allergens using in vitro methods. Future research areas such as novel fish species/allergens and ex vivo/in vivo evaluation methods would convey a comprehensive view of the relationship between processing and fish allergy.

IgE-Mediated Fish Allergy in Children

Fish allergy constitutes a severe problem worldwide. Its prevalence has been calculated as high as 7% in paediatric populations, and in many cases, it persists into adulthood with life-threatening signs and symptoms. The following review focuses on the epidemiology of Immunoglobulin E (IgE)-mediated fish allergy, its pathogenesis, clinical manifestations, and a thorough approach to diagnosis and management in the paediatric population. The traditional approach for managing fish allergy is avoidance and rescue medication for accidental exposures. Food avoidance poses many obstacles and is not easily maintained. In the specific case of fish, food is also not the only source of allergens; aerosolisation of fish proteins when cooking is a common source of highly allergenic parvalbumin, and elimination diets cannot prevent these contacts. Novel management approaches based on immunomodulation are a promising strategy for the future of these patients.