House CallApril/May 2008 Issue

QA- Allergies and Food Sensitivities

Q. Can a child or adult be allergic to sunflower seeds?

A. Absolutely. Everyone knows about peanut and tree nut allergies but few are aware that there are increasing numbers of individuals who demonstrate sensitivities to other seed products, such as sunflower, sesame, poppy and rapeseed. These seeds can cause severe anaphylaxis in people who are highly allergic to them. It can be challenging to avoid these items since they’re commonly used in foods and baked goods and aren’t as stringently labeled as peanuts or tree nuts.

Food Sensitivities

Q. I come from a family with lots of allergies. Now my doctor has ordered RAST blood work. What is RAST?

A. A radioallergosorbent test, or RAST, is a standardized test that’s used to confirm the presence of a food or environmental allergy. This test, conducted by a certified medical laboratory, ascertains the presence in the blood of certain IgE antibodies, the specific allergic component of a food or allergen. In some cases, the test can also help predict the chance that an allergy will intensify or be outgrown. To ensure accuracy, RAST results require careful interpretation by a healthcare provider with expertise in
food allergies.

Q. What’s the difference between celiac disease and an IgE-mediated wheat allergy?

A. These are two distinct disorders. Celiac disease, or gluten-sensitive enteropathy, is a hereditary, auto-immune disease. Approximately 1 in 133 Americans have this condition which is triggered by the ingestion of gluten, proteins found in wheat, rye and barley. Celiac disease is frequently misdiagnosed because its symptoms can vary. Some people have minimal or no symptoms but common reactions can include bloating, abdominal pain, anemia, unusual weight loss, fatigue, depression, diarrhea, osteoporosis, and sometimes an itchy, red skin rash (dermatitis herpetiformis). As gluten is ingested, the effects of the disease flatten the villi in the intestines, causing malabsorption. Celiac disease is diagnosed by blood work and by examining tissue samples from the intestine. The only treatment for celiac disease is the maintenance of a strictly gluten-free diet. Left untreated, celiac disease can cause infertility and other serious health problems.

An IgE-mediated wheat allergy is a true food allergy. Basically, it’s a hypersensitivity to the immunoglobulin E (IgE) antibodies in wheat that trigger mast cells to release histamine and cause tissue inflammation and swelling. Like an allergic reaction to peanuts or shellfish, a person with a wheat allergy can develop a range of symptoms after ingesting wheat, such as hives, difficulty breathing, a drop in blood pressure, anaphylaxis and even death.
Q. How long after ingestion can I expect an allergic reaction?

A. Most IgE-mediated reactions occur within 30 minutes to an hour after eating the offending food. But there are exceptions; sometimes a reaction occurs within a few minutes. Occasionally, there can be delayed reactions, where a second reaction happens up to 12 hours after the initial reaction. These delayed reactions usually are associated with a severe initial reaction. Reactions that occur days to weeks after ingestion aren’t usually related to an allergy and may have other causes.

Food Sensitivities

Q. What’s the difference between allergic sensitization and an allergic reaction? 

A. Sensitization is when the immune system recognizes a particular allergen but doesn’t always respond to it. Reaction is the immune system’s response to an allergen.

Q. Why does my doctor want my 2-year-old daughter to avoid eating cake with eggs when she only reacts to whole eggs? Does it have to do with sensitization?

A. Yes. In some food-allergic kids, sensitization can occur without an apparent reaction. If you’re allergic to a food, exposure to even small amounts of it can be problematic. Doctors hope that an immature immune system can be molded into a less reactive state. That’s why an allergist will ask a family to completely eliminate a particular allergen from a young child’s diet; it improves the chances of desensitization over time. 

Q. My child refuses to eat certain foods, mostly baked goods and noodles. Does this mean he has a food allergy?

A. It depends. I’ve seen some allergic kids who become aware of very vague symptoms they can’t fully explain and they refuse to eat a particular food, usually eggs. But don’t jump to conclusions. It’s normal behavior for young children to have strong likes and dislikes of various foods. Simply refusing to eat an item isn’t evidence of an allergy. If you’re suspicious, discuss your concerns with your child’s primary care physician or pediatric allergist.

Q. Can you suggest any good books for families with food allergies?

A. I often recommend Food Allergies for Dummies by Robert A. Wood, M.D., at Johns Hopkins University School of Medicine and Understanding and Managing Your Child’s Food Allergies by Scott H. Sicherer, M.D., at Mt. Sinai Medical Center’s Department of Pediatrics. Both books are easy to read and contain lots of very useful information. I also refer families to the Food Allergy and Anaphylaxis Network (FAAN) at

Q. I’ve have heard about a new type of treatment where medication is placed under the tongue to cure allergies. Is this better than allergy shots?

A. Sublingual (under the tongue) immunotherapy is similar to traditional injected immunotherapy (i.e., allergy shots). In both methods, your doctor is trying to desensitize the immune system by giving increasing amounts of a specific allergen protein. If administered correctly over time, injected allergy shots can be very successful in reducing traditional allergy symptoms, such as itchy eyes, runny nose and congestion. Treatment with allergy shots has been available for decades. Recently, sublingual immunotherapy has been attempted in Europe. This method, which has some promise, is currently under investigation to ascertain its effectiveness. At this time, the U.S. Food and Drug Administration and major allergy organizations have not approved sublingual immunotherapy for treatment of either seasonal or food allergies. There are early-phase studies examining this treatment for food allergies but we’re still several years away from widespread use.  LW

Harvey L. Leo, M.D. is a pediatric allergist with Allergy and Immunology Associates in Ann Arbor, Michigan. He also holds an academic position at the University of Michigan School of Public Health.

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