Food Allergy: What are the symptoms on the skin?

Although it is challenging to assess the prevalence of food allergies, it appears to be increasing year after year. As a reminder, a food allergy is defined as a immune response to a food protein. It should not be confused with immune-mediated reactions, such as lactose or gluten intolerances. While food allergies can occur with any food, it is interesting to note that the allergens responsible for more than 85% of food allergies are milk, eggs, peanuts, nuts, shellfish, fish, wheat, sesame, and soy.

There are two main categories of food allergies: those mediated by immunoglobulin E antibodies and those that are not. The former are the most common and are characterized by the rapid onset of symptoms after ingestion. During the initial sensitization to a food, the consumption of the allergenic food protein stimulates the production of IgE antibodies specific to that food, which then attach to basophils and mast cells in the tissues. When the offending food is subsequently consumed, it binds to its specific IgE antibodies and triggers the release of inflammatory mediators, such as histamine, prostaglandins, and leukotrienes, thereby causing allergic symptoms.

Cell-mediated food allergy, that is, non-IgE, is less common and results from the generation of T lymphocytes, specialized immune cells that directly respond to the allergenic food protein. In doing so, T lymphocytes trigger the release of mediators that direct inflammatory responses, such as eosinophilic inflammation.

Skin reactions are the most common clinical manifestations of food allergies and include the hives, swelling, and redness.