Myths and facts about food allergies

Kids eating lunchBARABOO | An estimated 15 million Americans suffer from food allergies. To help clear up the facts about food allergy, Dean Clinic allergist Dr. Christine Virnig shares four top myths and the truth about these common misconceptions.

Myth 1: All food related adverse reactions are due to an “allergy.”
Fact: “Food intolerances and food allergies are often confused,” Virnig said. “A food allergy is a specific immune response in which a person’s immune system produces IgE (the allergy antibody) against a food. Food allergies lead to rapid onset, reproducible, and potentially life-threatening reactions.”
Typical symptoms of a food allergy include hives, throat swelling, a hoarse voice, coughing, wheezing, abdominal cramping, nausea, and vomiting. In contrast, food intolerances are adverse food reactions that are not mediated by IgE, the allergy antibody. Typical symptoms of food intolerance include stomach upset, bloating, cramps, nausea, and vomiting.
“Eating a food you are intolerant to can leave you feeling miserable, but eating a food you are allergic to can be life-threatening,” Virnig said.
The prevalence of food allergy is perhaps 3 to 8 percent of children and less than 2 percent of adults. This is far less than reported food intolerance, which can occur in up to 30 percent of the population. There seems to be an increasing prevalence of food allergy, particularly to peanuts and tree nuts, in children over the past decade. Unfortunately the factors responsible for this are unknown.
The most common food allergens in the U.S. are peanuts, tree nuts, milk, egg, wheat, soy, fish and shellfish. Allergies to these foods are usually caused by specific proteins found in the food products.
Myth 2: If a person is allergic to shellfish they are allergic to iodine.
Fact: There is no relationship between the shellfish allergen, which is a muscle protein, and iodine. A person allergic to shellfish has no increased risk of reacting to x-ray contrast involving iodine compounds.
“Years ago doctors believed that shellfish allergies stemmed from the increased amounts of iodine present in shellfish, so patients with a shellfish allergy were told to avoid iodine and iodine-based contrast dyes,” Virnig said. “Now we know that people who are allergic to shellfish are actually allergic to the proteins found in shellfish, not the iodine. There is about a three percent chance that a person who is allergic to shellfish will have a reaction to contrast dyes, but this percentage is about the same in people with no known shellfish allergy.”
Myth 3: With each exposure to a food allergen, the reaction is likely to get worse.
Fact: Although a reaction is likely to occur in a patient who is exposed to a food that they are allergic to, the severity can be highly variable and unpredictable. It may depend on whether the allergen was ingested, inhaled or contacted a skin area. Risk factors for more severe reactions may include a history of asthma, alcohol use and/or concomitant exercise.
Food allergies most commonly present in childhood during the first few years of life, but allergies to shellfish or fish may develop in adulthood. Allergies to milk, egg, wheat and soy are often outgrown, while allergies to peanuts, tree nuts, and seafood usually persist. Children allergic to eggs and milk may be able to tolerate these foods if they are heated, such as in baked goods.
Like most everything else in the medical field, the diagnosis of food allergy starts with a careful history. This should include a list of the possible foods suspected, the route of exposure, (oral, ingested, or topical), the timing of the onset of symptoms after exposure and details of the specific symptoms and their severity. It is also important to note if this has happened more than once with contact with the suspected food.
“To diagnose a food allergy we need both a history suggestive of a food allergy and a positive allergy test to the food in question,” Virnig said. “Many people believe that if you have a positive allergy test to a food you are definitely allergic, but unfortunately things are not that straightforward. False positive allergy tests are very common, and frequently a person with positive allergy tests can actually eat the food without having symptoms. This is why having a history suggestive of a food allergy is an important part of the equation. If there is no such history, or if the history is uncertain, we often challenge a person to the food in question to see if they tolerate the food or not.”
Skin prick testing is one of the more common methods used to aid the diagnosis of a specific food allergy. This is done by placing a small drop of the food extract or material on the skin and making a tiny puncture. Results can be determined within 15 minutes and are dependent on the size of the wheal and flare response. Caution is necessary since very sensitive patients may experience a systemic allergic reaction to testing.
Food allergy testing can also be done by obtaining a sample of blood, but these tests may be more expensive and it usually takes several days for the results to become available. After a diagnosis of a specific food allergy is made, the primary therapy is strict avoidance of that food or foods.
Patients, their families, and other caregivers need to be educated on how to read food labels and how to ask whether prepared foods might contain the allergen. Younger children should be taught to never share food, unless it is from a trusted source. All patients should have self-injectable epinephrine (an EpiPen or Auvi-Q) always available and should have a medical alert bracelet or tag they can wear.
Myth 4: Allergic reactions to food can safely be treated with antihistamines such as Benadryl.
Fact: Epinephrine is always the drug of choice to treat an allergic emergency. Epinephrine works quickly and can stop an allergic response more completely than antihistamines such as Benadryl. Fatalities due to severe food allergy are more common when there is a delay in the administration of epinephrine or a false reliance on antihistamines.
When it comes to treating someone who suffering from a life-threatening allergic reaction, Virnig said immediate administration of epinephrine is key.
“If epinephrine is available, administer the epinephrine and call 911,” Virnig said. “If epinephrine is not available, call 911 so that epinephrine can be brought to the patient as quickly as possible. It is OK to administer antihistamines while waiting for the paramedics to arrive.”
There is currently no other approved treatment for food allergy other than careful avoidance, although there is promise of better therapy in the future. It remains unclear whether restricting the mother’s diet during pregnancy or breast feeding affects the development of food allergy in their children. Breast feeding for at least four to six months after birth is commonly recommended.
Although food allergy can be serious, understanding and careful planning can greatly minimize any risks and allow patients to live a normal and nutritionally sound life.

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