A food allergy is when the bodys immune system reacts unusually to specific foods, treating proteins found in food as a threat and releasing a number of chemicals that cause the symptoms of an allergic reaction. The most common type of food allergy is IgE-mediated food allergy, which is triggered by the immune system producing an antibody called immunoglobulin E (IgE). Almost any food can cause an allergic reaction, but there are certain foods that are responsible for most food allergies. The eight most common allergenic foods are milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soybeans. In children, the foods that most commonly cause an allergic reaction are cows milk, eggs, peanuts, tree nuts, soy, and wheat. In adults, the foods that most commonly cause an allergic reaction are peanuts, tree nuts, fish, and shellfish.

It is important to note that food intolerance is different from food allergy. Food intolerance occurs when the body has a chemical reaction to eating or drinking some foods, and it is not an immune response. The most common foods to cause a reaction for people with a food intolerance are foods containing glutamate, amines, and salicylates.

In summary, the component of a food that is responsible for an allergic reaction is a protein that the immune system mistakenly treats as a threat, causing the release of chemicals that trigger the allergic reaction. The specific protein can vary depending on the individual and the food, but the most common allergenic foods are milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soybeans.