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15 Facts About Every Type of Food Allergy

Understanding the real deal about food allergies can keep you—and your family—healthy and safe.

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A widespread problem

Nearly one in ten Americans have an allergy to one or more foods—32 million people. Peanuts, milk, and shellfish are among the most common trigger foods, and a reaction can range from mild (an itchy mouth after you eat the food) to severe (throat closing, difficulty breathing—called anaphylaxis); in rare cases, a food allergy can be fatal if the patient doesn’t get treatment quickly enough. And food allergies are just one of the 7 allergies that are on the rise.

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What is a food allergy?

Basically, it’s when your body’s immune system overreacts to a food protein, says Kira Geraci-Ciardullo, MD, an allergy and asthma specialist with White Plains Hospital Medical & Wellness in Armonk, New York. The body’s immune system is designed to attack invaders, such as bacteria and viruses; sometimes it mistakenly attacks something harmless—such as a protein in food. Initially, the reaction could be mild—a rash, an itchy mouth—but it can get worse the more you have of the food. Your body can release a flood of immune-fighting substances called IgE antibodies (or immunoglobulin E) to fight against the food allergen, which in turn trigger hives, a dangerous drop in blood pressure, and tightening of your airways.

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Mysteries about food allergies

Not everyone who has an IgE reaction to food will develop a serious food allergy, according to Food Allergy Research & Education (FARE). Some people can have a mild reaction after exposure to a food, and then a violent response the next time. Experts aren’t sure why there is such variation. There can be a genetic component: If a parent is allergic to a food, the child is more prone to also being allergic to it, says Dr. Geraci-Ciardullo. People with other types of allergic reactions—such as eczema, asthma, or hay fever—are also more prone to food allergies, reports to FARE.

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Most common offenders

People can be allergic to more than 170 foods, but eight are responsible for the majority of allergies in the United States: milk, egg, peanut, tree nuts, soy, wheat, fish and shellfish. “If you look at emergency room records of anaphylaxis, the most common cause is food allergies,” says Dr. Geraci-Ciardullo. “And of those anaphylactic reactions caused by food allergies, the most common foods are peanuts or tree nuts in children and fish or shellfish in adults.” Here are more common foods that cause allergies.

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Diagnosing food allergies

Allergists use two main methods to diagnose food allergies: A skin-prick test (in which the skin is punctured with water-based extracts of different allergens to see if the patient responds—typically in the form of a small hive), and a blood test to measure the IgE antibody. The IgE test is measured on a scale of 1 to 100. “Generally, the higher the number, the more nervous we are about your allergy,” says Dr. Geruci-Ciardullo.

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One of the most common and confusing allergies is a peanut allergy. It’s on the rise among children and can cause an anaphylactic reaction in tiny doses—even through skin or airborne contact, according to FARE. While a peanut allergy tends to be lifelong, one in five children do outgrow it.

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Early exposure—or not?

Allergists used to recommend that parents keep peanuts away from children for the kids’ first three years of life. That thinking has changed thanks to a British study done on Israeli children—these infants typically get peanut lollipops when they’re four to five months old as part of cultural practice. The children in the study who were given peanuts early never had problems, while children who got their first peanut exposure later were more likely to develop an allergy. Experts now recommend not waiting: “Introduce peanut whenever you’re comfortable introducing it,” says Dr. Geraci-Ciardullo.

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EpiPen—or not?

Some people who are allergic to peanuts never have an anaphylactic reaction. Yet doctors still prescribe them an EpiPen—an injectable dose of epinephrine and the first-line treatment for anaphylaxis. Without the shot, someone who goes into anaphylactic shock could die. But does everyone with a peanut allergy need it? “We always assume the worst could happen,” says Dr. Geraci-Ciardullo. “We don’t know the circumstances in which eating a peanut will cause hives and vomiting vs. death. We don’t take the chance.” Just because you have a mild reaction once doesn’t mean it won’t be worse the next time.

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Tree nuts

If you’re allergic to peanuts, you have a 25 to 40 percent greater risk of being allergic to tree nuts (such as walnuts, hazelnuts, and almonds). And this allergy can lead to an anaphylactic reaction. Fewer than 10 percent of people with this allergy outgrow it. Other symptoms include abdominal pain, cramps, nausea, vomiting, diarrhea, difficulty swallowing, and itching of the mouth, throat, eyes, or skin. Your reaction may not be to the nuts, however: Check out 20 bizarre things people can be allergic to.

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Oral allergy syndrome

Sometimes people who have a well-established allergy to pollen develop something called oral allergy syndrome—a reaction to certain fruits and nuts that have proteins in them that cross-react with the proteins in pollen, says Dr. Geraci-Ciardullo. The reaction only occurs with raw fruits and nuts. “Once you cook the fruit or roast or bake the nuts, you won’t have a reaction,” she says. To determine whether someone has this syndrome versus a true food allergy, doctors can do allergen component testing (ACT). The test gives more specific results than a skin-prick challenge and can help you and your doctor develop a more comprehensive allergy plan. “Component testing is the wave of the future,” says Dr. Geraci-Ciardullo. Here’s some more useful information about oral allergy syndrome you didn’t know about.

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Milk, egg, and wheat

These allergies are common in childhood but people generally outgrow them. “It’s unusual to have a child who, at age 5, retains an allergy to egg, wheat, or milk,” says Dr. Geraci-Ciardullo. “There’s a few but not many.” You shouldn’t assume children have outgrown these allergies if they reach age 5, however. “They need to be retested.”

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Fish and shellfish

People tend to develop these allergies in adulthood and the reaction can be anaphylactic, according to FARE. The fish likely to trigger an allergy include tuna, halibut, and salmon; the shellfish include shrimp, crab, lobster, mussels, oysters, clams, snails, and squid. Some people are allergic to one or the other, and some are allergic to both. Fish is also a common ingredient in things you may not suspect, such as Worcestershire sauce and Caesar salad. Experts recommend strict avoidance if you have either or both of these allergies.

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“Allergies to sesame are becoming more of an issue,” says Dr. Geruci-Ciardullo. Some reports have suggested that this allergy has increased worldwide over the last two decades, according to FARE, although researchers aren’t sure yet why that’s the case. Offenders can include sesame seed, sesame oil, sesame paste, sesame flour, and tahini. These ingredients are commonly used in Asian, Turkish, and other ethnic cuisines. You can protect yourself by learning what allergists do to control their own allergies.

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Many people exhibit sensitivity to dyes and other chemicals found in foods. But there is no skin or blood test to confirm this type of allergy. “These allergens tend to be not proteins but small, inorganic chemicals,” says Dr. Geruci-Ciardullo. “It’s a chemical reaction rather than an immunologic reaction.” And therefore, more difficult to diagnose. “There’s a lot of detective work,” she says.

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Staying safe when you have food allergies

The only treatment for a food allergy is avoidance. “If you have a food allergy, avoid that food,” says Dr. Geruci-Ciardullo. She may prescribe an antihistamine (such as Benadryl) and an EpiPen to certain patients, to be used in case of a mild or severe reaction. These 13 dangerous myths about food allergies provide more crucial information that you should know.