Food Allergy (cont.)

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What are the most common food allergies?

In adults, the most common foods that cause allergic reactions are shellfish, such as shrimp, crayfish, lobster, and crab; nuts from trees, such as walnuts; fish; eggs; and peanuts, a legume that is one of the chief foods that cause serious anaphylactic reactions. In highly allergic people, even minuscule amounts of a food allergen (for example, 1/44,000 of a peanut kernel) can evoke an allergic reaction. Less sensitive people, however, may be able to tolerate small amounts of a food to which they are allergic.

In children, the pattern is somewhat different from adults, and the most common foods that cause allergic reactions are eggs, milk, peanuts, tree nuts, shellfish, soy, fish, and fruits, particularly tomatoes and strawberries. Children sometimes outgrow their allergies, but adults usually do not lose theirs. Also, children are more likely to outgrow allergies to cow's milk or soy formula than allergies to peanuts, fish, or shrimp. Adults and children tend to react to those foods they eat more often. For example, in Japan, allergy to rice, and in Scandinavia, allergy to codfish, is more common than elsewhere.

What is cross-reactivity?

Cross-reactivity is the occurrence of allergic reactions to foods that are chemically or otherwise related to foods known to cause allergy in an individual. If someone has a life-threatening reaction to a certain food, the doctor will counsel that patient to avoid related foods, which also might induce the same reaction. For example, if a person has a history of a severe allergy to shrimp, he or she can also possibly be allergic to crab, lobster, and crayfish.

What is oral allergy syndrome?

The oral allergy syndrome is another type of cross-reactivity. This syndrome occurs in people who are highly sensitive, for example, to ragweed or birch pollen. During the seasons that these allergens pollinate, the affected individual may find that when he or she tries to eat fruits, chiefly melons and apples, a rapid onset of itching is experienced in the mouth and throat, and the fruit cannot be eaten. The oral allergy syndrome is also known as pollen-food allergy syndrome and is thought to be a type of contact allergy related to the presence of proteins in certain foods that cross react with allergy-causing pollen proteins. Oral allergy syndrome occurs in up to 50% of those who have allergic rhinitis caused by pollen. Symptoms are immediate upon ingestion of fresh or uncooked foods and include the itching, irritation, and mild swelling of the lips, tongue, palate, and throat. Cooked fruits and vegetables usually do not cause the reaction. The symptoms usually go away within minutes, although up to 10% of people will develop systemic (body-wide) symptoms, and a small number (1%-2%) may experience anaphylactic shock. Tree nuts and peanuts tend to cause more severe reactions than other foods.

Medically Reviewed by a Doctor on 3/24/2014

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