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You’ve heard scary food allergy stories, and maybe this has even happened to you or someone you know: an innocent bite of a sandwich, casserole, soup, or salad is suddenly followed by shortness of breath, a rash, sweating, or some other sign of an anaphylactic reaction.
How do food allergies develop? Do they start only in childhood, or can you develop one later in life? What predisposes some people to food allergies?
According to the Food Allergy and Anaphylaxis Network (FAAN), a food allergy is the response of the immune system to a food that the body mistakenly believes is harmful. The body creates antibodies to that food, and the next time the allergic person eats the food, the immune system releases massive amounts of chemicals, including histamine, to protect the body. These chemicals trigger a cascade of allergic symptoms that can affect the respiratory system, the gastrointestinal tract, the skin, and the cardiovascular system.
How Food Allergies Develop
Allergy-related immunoglobulin E (IgE) is the antibody found in our blood and tissues that mediates allergy. Allergy sufferers have raised levels of IgE, which can be measured in the blood by various tests. Specific types of allergy tend to be related to age. Allergy to milk and egg whites is common among young children and it tends to subside naturally with time. Peanut and fish allergies tend to persist throughout life, and levels of specific peanut IgE remain high in people who are allergic to peanuts. (Allergies to tree and grass pollen, on the other hand, arise later in childhood and peak in early adolescence.)
Eight foods account for 90 percent of all food-allergic reactions, FAAN reports: milk, eggs, tree nuts (walnuts, cashews, etc.), peanuts, fish, shellfish, soy, and wheat. However, in children, the most common food allergens are peanuts, shrimp, and milk; about 6 percent of children have an allergy to tree nuts.
Allergic reactions to food, whether experienced by adults or children, can include itchy hives and vomiting as well as gasping for breath.
Who’s Allergic?
Bruce M. Penner, MD, an allergist and an associate clinical professor in the department of pediatrics at the University of California at San Diego, says a family history of asthma, hay fever, or atopic dermatitis increases the likelihood that a person will develop a food allergy.
“Children may develop a food allergy in infancy or the very first time they eat a certain food, but it’s more common that the reaction occurs after the second, third, or subsequent exposure,” Dr. Penner says. This is because initial exposure does not usually produce enough IgE to spark a noticeable or dangerous reaction. “And the full-blown reaction may need a few exposures of the food to become apparent.”
Full-blown reactions usually occur as a result of eating — and sometimes even touching or smelling — shellfish, fish, and tree nuts. An allergy to those foods, Penner says, can develop at any time in life, whereas allergies to milk, soy, corn, and eggs tend to develop in children who are 4 and younger.
Susan Kraus, a nutritionist in the Allergy & Immunology Center at Hackensack University Medical Center in New Jersey, says one reason allergies to milk and corn occur in children so young is early exposure. “These are common things given to children,” she says. “Shrimp and lobster usually aren’t.”
Ayesha Siddiqi, MD, an allergist at Advocate Illinois Masonic Medical Center in Chicago, says that if an immediate family member has a food allergy, that can up the odds that a person will develop some type of food allergy. “If one child has food allergies, there is a 20 to 35 percent chance that their sibling will develop allergies. A parent with food allergies creates a 25 to 40 percent chance that an offspring will be allergic.” What if both parents have food allergies? Dr. Siddiqi says that such a situation raises the chance of allergies in an offspring to 40 to 60 percent.
Penner cautions genetics aren’t a conclusive link: “The truth is we do not know what combination of genetics and environmental exposure triggers food allergies.”
Nice huh? Make sure you’ll be aware of food allergy!
Take care
Source: http://www.everydayhealth.com/health-report/allergy/food-allergies.aspx