Seafood allergy is a serious food allergy, especially in coastal regions and fish processing communities where seafood is a common constituent of the diet. Besides peanuts and tree nuts, fish and shellfish are among the most frequent causes of IgE-mediated allergic reactions in adolescents and adults.

The major allergen of crustaceans such as shrimp, crab, and lobster, has been identified as the muscle protein tropomyosin. Invertebrate tropomyosins are pan-allergens with significant sequence similarity identified in seafood and insects such as storage and house dust mites and cockroaches.

Consequently, tropomyosins are also found as aeroallergens, which raises the possibility of sensitization by the respiratory route. Parvalbumins have been identified as the major allergens of fish that are recognized by IgE of more than 95% of fish-allergic individuals.

Cows’ milk is the first foreign antigen source ingested in large quantities in early infancy. Consequently, cows’ milk allergy (CMA) is a common disease of infancy and childhood. The incidence of CMA in infancy is approximately 2–3% in developed countries. Normally, children outgrow their milk allergy.

After acidification or chymosin treatment, cows’ milk proteins can either be found in the lactoserum (whey) or the coagulum (curd). Whey contains essentially globular proteins, the major ones being beta lactoglobulin, alpha-lactalbumin, and bovine serum albumin. The curd fraction comprises the caseins.

Beef allergy is rare. A higher prevalence of beef allergy might be expected among children allergic to milk, because both foods contain bovine serum albumin, bovine gamma globulin, and other proteins in significant quantities.

Patients clinically reactive only to rare beef had decreased IgE binding to beef fractions compared with patients reactive to well-cooked beef. Therefore, patients reacting only to rare beef would not necessarily have to maintain a complete beef elimination diet.

Hen’s egg is another food most frequently reported to elicit allergic reactions in children. Egg white protein contains 23 different glycoproteins. Ovomucoid (Gal d 1), ovalbumin (Gal d 2), ovotransferrin (Gal d 3), and lysozyme (Gal d 4) have been identified as the major allergens, but ovomucoid has been shown to be the dominant allergen

Cross-reactions among various avian eggs have been described and reactions to duck and goose egg in the absence of hen’s egg allergy have also been reported. Reports of allergy to bird meats are not common. Most cases have been observed in patients with ‘bird-egg syndrome’ that is based on the presence of alphalivetin in egg yolk, feathers, and serum (chicken serum albumin).

A subset of the patients with ‘bird-egg syndrome’ are also allergic to chicken meat possibly due to the serum proteins present in the meat. Another category of patients is allergic to chicken meat but not to egg. Patients allergic to one bird’s meat may be allergic to others, including game birds. However, allergy to chicken meat is quite rare and allergy to turkey is even less common.