Reactions that imitate food allergy may occur in adults. Food intolerance is a non-immune reaction after ingestion of a food and is often misinterpreted by patients as a food allergy. We wrote this article to explain the situations that are confused with food allergy.

What is food intolerance?

Food intolerance may occur with exposure to metabolic substances (eg lactose intolerance); due to exposure to toxins in food (for example, microbial contamination or scombroid fish poisoning) or other metabolically active components of food; such as caffeine or tyramine (found in aged cheeses), which can trigger migraines. These reactions may also occur through unspecified mechanisms. A detailed history, as described earlier, can help differentiate food intolerance from food allergy; however, referral to an allergist and further testing are required in many cases.

Histamine Reactions

Two other types of reactions may mimic the classic IgE-mediated food allergy to seafood. The initial reaction is caused by scombroid (Histamine) poisoning, a non-IgE-mediated reaction that mimics a classic allergic reaction. This reaction is typically due to mishandling of fish. While the symptoms are the same as a true allergic reaction, such as flushing, itching, and even shortness of breath, they do not recur, unlike IgE-mediated reactions that occur every time the culprit fish is ingested.

Tropomyosin susceptibility

Another type of reaction to seafood is from sensitivity to tropomyosins, which are major allergens in crustaceans. Tropomyosins from shellfish and fish have a high degree of homology with house dust mites and cockroaches. Shrimp tropomyosin (Pen a 1) has more than 80% amino acid sequence similarity to house dust mite (Der p 10) and cockroach (Per a 7) Shellfish tropomyosins extensively cross-react with tropomyosins in dust mites and cockroaches.

Similar to the oral allergy syndrome reaction to fruits and vegetables that cross-react plant allergens, it has been hypothesized that shellfish allergy in adolescents and adults may be secondary to sensitization to inhalant allergens, including dust mite and cockroach, containing a cross-reacting tropomyosin. These reactions are usually only cutaneous, milder, and occur with greater cross-reactive ingestion of food, which distinguishes it from classical IgE-mediated food allergy where ingestion of smaller amounts of food (one bite) can result in anaphylaxis.

Recently, delayed reactions to seafood resembling food protein-induced enterocolitis syndrome in adults have been reported. Although the mechanism of these reactions is not fully understood, it may be linked to sensitivity to these cross-reactive epitopes.

As a result;

  • There are some food reactions that are confused with food allergies in adults.
  • The most common conditions involved in adult food allergies are food intolerance, reactions to histamine, and sensitivity to tropomyosin.