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- Food allergy facts
- What is a food allergy?
- What causes allergic reactions to food?
- What are food allergy symptoms and signs?
- What are food allergy risk factors?
- Do infants and children have problems with food allergy?
- What are the most common food allergies?
- What is cross-reactivity?
- What is oral allergy syndrome?
- What is exercise-induced food allergy?
- What conditions have mistakenly been attributed to food allergy?
- What conditions mimic food allergy?
- How is food allergy diagnosed? What tests are used to diagnose food allergies?
- What is the treatment for a food allergy?
- Are allergy shots effective in preventing or decreasing food allergy?
- What is the prognosis (outlook) for food allergy?
Quick GuideAllergy Pictures Slideshow: Common Food Allergy Triggers & Where They Hide
What causes allergic reactions to food?
Both heredity and environmental factors may play a role in the development of food allergy. The allergens in food are those ingredients that are responsible for inciting an allergic reaction. They are proteins that usually resist the heat of cooking, the acid in the stomach, and the intestinal digestive enzymes. As a result, the allergens survive to cross the gastrointestinal lining, enter the bloodstream causing allergic reactions throughout the body. The mechanism of food allergy involves the immune system and heredity.
Immune system: An allergic reaction to food involves two components of the immune system. One component is a type of protein, an allergy antibody called immunoglobulin E (IgE), which circulates through the blood. The other is the mast cell, a specialized cell that stores up histamine and is found in all tissues of the body. The mast cell is particularly found in areas of the body that are typically involved in allergic reactions, including the nose and throat, lungs, skin, and gastrointestinal tract.
Heredity: The tendency of an individual to produce IgE against something seemingly as innocuous as food appears to be inherited. Generally, people with allergies come from families in which allergies are common -- not necessarily to food but perhaps allergies to pollen, fur, feathers, or drugs. Thus, a person with two allergic parents is more likely to develop food allergies than someone with one allergic parent.
Mechanism: Food allergy is a hypersensitivity reaction, meaning that before an allergic reaction to an allergen in food can occur, a person needs to have been exposed previously, or "sensitized," to the food. At the initial exposure, the allergen stimulates lymphocytes (specialized white blood cells) to produce the IgE antibody that is specific for the allergen. This IgE then is released and attaches to the surface of the mast cells in different tissues of the body. The next time the person eats that particular food, its allergen hones in on the specific IgE antibody on the surface of the mast cells and prompts the cells to release chemicals such as histamine. Depending upon the tissue in which they are released, these chemicals cause the various symptoms of food allergy.