Food Allergy

Introduction

The ingestion of specific food and food products induce a wide range of adverse reactions ranging from mild to life-threatening anaphylaxis. The etiology is multifactorial, involving complex interactions between genetic predispositions, environmental exposures, and immune system dysregulation. According to reports, the incidence of allergic reactions in adults is about 5%, and the incidence in children is as high as 8%. Therefore, accurate identification of allergenic foods is critical for patient safety and for ensuring compliance with food labeling regulations.

Fig. 1 Food allergy represents a significant health issue.
(Muraro A.; et al. Allergol Select . 2022)

Mechanisms of Food Allergy

IgE mediated food allergy (type I hypersensitivity) can be divided into two phases; a sensitisation and an elicitation phase. Sensitisation usually occurs by a primary exposure to the given dietary protein, where oral tolerance induction fails or is abrogated and where naïve B cells are primed to become IgE secreting plasma cells. Allergen-specific IgE antibodies then bind to the high affinity receptor FcεRI on tissue mast cells and blood basophils, and upon reexposure to the offending dietary protein, cross-linking of FcεRI-bound IgE occur. This leads to degranulation of mast cells or basophils, releasing mediators, inducing the allergic symptoms characteristic of food allergy.

Fig. 2 Food allergy mechanism.
(Zhang J.; et al. Micromachines (Basel) . 2021)

Non-IgE-Mediated food allergy activate T-cells and other immune cells, leading to inflammation and tissue damage without the involvement of IgE. These reactions are typically delayed and manifest as gastrointestinal or dermatological symptoms.

Common Food Allergens

Food allergens can be broadly categorized into three main groups based on their sources:

Fig. 3 Structures of common food allergen.
(Sathe SK.; et al. Annu Rev Food Sci Technol . 2016)

Tree Nuts and Peanuts

Nuts, such as almonds, cashews, walnuts, and peanuts, are among the most common triggers of severe allergic reactions. These allergens are rich in storage proteins, including vicilins and legumins, which are highly resistant to heat and digestion, making them potent sensitizers. Specific allergenic proteins include Ara h 1, Ara h 2, and Ara h 3 in peanuts; Brazil nut 11S globulin (Ber e 1); and PECAN 11S globulin (Car i 4).

Animal-Derived Foods

Proteins from milk, eggs, fish, shellfish, and meat can also trigger allergic responses. Key allergens include casein and whey proteins (e.g., beta-lactoglobulin) in milk, ovomucoid (Gal d 1) in eggs, parvalbumin in fish, and tropomyosin in shellfish. Tropomyosin, for instance, is a heat-stable protein present in crustaceans like shrimp and lobsters, making it a frequent cause of allergic reactions even after cooking.

Aquatic and Seafood

Seafood allergens include a wide range of proteins from finfish, crustaceans, and mollusks, many of which are highly resistant to heat and digestion. Key allergens include parvalbumins (e.g., Gad c 1 in cod, Sal s 1 in salmon) in fish and tropomyosins (e.g., Lit v 1 in whiteleg shrimp, Scy p 1 in mud crab) in shellfish. Additional allergens such as arginine kinase (Cra g 1 from oyster) and hemocyanin contribute to the complexity of seafood allergy profiles.

Aquatic and Seafood

Seafood allergens include a wide range of proteins from finfish, crustaceans, and mollusks, many of which are highly resistant to heat and digestion. Key allergens include parvalbumins (e.g., Gad c 1 in cod, Sal s 1 in salmon) in fish and tropomyosins (e.g., Lit v 1 in whiteleg shrimp, Scy p 1 in mud crab) in shellfish. Additional allergens such as arginine kinase (Cra g 1 from oyster) and hemocyanin contribute to the complexity of seafood allergy profiles.

Fruits and Vegetables

Although less common than nuts or animal products, certain fruits and vegetables, such as apples, kiwis, and celery, can cause allergies. These reactions are often associated with cross-reactivity between food proteins and pollen allergens, a phenomenon known as oral allergy syndrome (OAS). Specific proteins involved include Mal d 1 in apples, Pru p 1 in peaches, and Api g 1 in celery. In most cases, cooking denatures these allergens, reducing their potential to elicit allergic responses.