Information from the National Institute of Health
A food allergy is an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.
Food allergens are the parts of food or ingredients within food (usually proteins) that are recognized by immune cells. When an immune cell binds to a food allergen, a reaction occurs that causes the symptoms of food allergy.
What you should know
Most food allergens cause reactions even after they have been cooked or digested. Some allergens, most often from fruits and vegetables, cause allergic reactions only when eaten raw. Food oils, such as soy, corn, peanut, and sesame, may or may not be allergenic (causing allergy), depending on how they are processed.
“Allergy” and “allergic disease” refer to conditions that involve changes to your immune system. These immune system changes fall into two categories:
- Immunoglobulin E (IgE) mediated—the symptoms are the result of an interaction between the allergen and a type of antibody, known as IgE, which is thought to play a major role in allergic reactions.
- Non-IgE mediated—the symptoms are the result of an interaction of the allergen with the immune system, but the interaction does not involve an IgE antibody.
If you are sensitized to a food allergen, it means that your body has made a specific IgE (sIgE) antibody to that food allergen, but you may or may not have symptoms of food allergy. If you can consistently tolerate a food that once caused you to have an allergic reaction, you have outgrown the food allergy.
Food intolerances are adverse health effects caused by foods. They do not involve the immune system. For example, if you are lactose intolerant, you are missing the enzyme that breaks down lactose, a sugar found in milk.
How common is food allergy?
A survey conducted by the Centers for Disease Control and Prevention estimated that food allergy affects five percent of children under the age of 5 and four percent of children aged 5 to 17 years and adults in the United States.
There are eight major food allergens in the United States—milk, eggs, peanuts, tree nuts, soy, wheat, fish, and crustacean shellfish.
Prevalence rates in the United States for some of these food allergens are provided below:
- Peanuts: 0.6 percent
- Tree nuts: 0.4–0.5 percent
- Fish: 0.2 percent in children and 0.5 percent in adults
- Crustacean shellfish (crab, crayfish, lobster, shrimp): 0.5 percent in children and 2.5 percent in adults
- All seafood: 0.6 percent in children and 2.8 percent in adults
- Milk and eggs: no reliable data available from U.S. studies, but based on data obtained outside the United States, this rate is likely to be 1–2 percent for young children.
Can food allergy be outgrown?
Most children eventually outgrow milk, egg, soy, and wheat allergy. Fewer children outgrow peanut and tree nut allergy. Outgrowing a childhood allergy may occur as late as the teenage years.
For many children, sIgE antibodies can be detected within the first two years of life. A child with a high initial level of sIgE, along with clinical symptoms of food allergy, is less likely to outgrow the allergy. A decrease in sIgE antibodies is often associated with outgrowing the allergy.
Food allergy can also begin in adulthood. Late-developing food allergy tends to persist.
What other conditions can occur with food allergy?
If someone has food allergy, he or she is more likely to have asthma, eczema, eosinophilic esophagitis (EoE), or exercise-induced anaphylaxis.
What are risk factors for severe allergic reactions to foods?
The severity of allergic reactions to foods is based on many different factors, including how much you ate and whether the food was cooked, raw, or processed. You cannot tell how severe your next allergic reaction will be based on the severity of your previous reactions.
No available tests can predict how severe a future allergic reaction will be. You are more likely to have a severe allergic reaction to food if you also have asthma.
For more information visit www.nih.gov
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