Q: Does it make sense to get tested after you have already excluded a possible food allergen? If yes, would we have to ingest the things we are allergic to for the testing to provide a result?

Background:  My wife is fortunate.  She can eat anything she wants.  At this point, the rest of us are envious. Our daughter decided she was gluten intolerant at age 11, then broadened to a corn, wheat intolerance with a focus on high fructose corn syrup.  At age 11 she was a walking diagnostic tool.  Flushing on her face, swelling of her nose and a head ache.  Without any question she is allergic to gluten and corn.

I have some symptoms that seem to be triggered by food, wheat and corn for the most part.  I eliminated these and felt much better and the rashes disappeared.

Our son believed he was not impacted by food allergies.  This year we were concerned because he was sickly and underweight.  His sister suggested that he might have some sort of diet-related condition.  He changed his diet, now he is gaining weight and looking better.  My son can tell within minutes if he has eaten something with high fructose corn syrup.  This seems to be a food ingredient that causes all three of us to immediately react severely.

Family History:  After my daughter had these problems, I discovered from my mother that other family members have similar problems.  My mother, uncles and grandfather all had strange allergies related to corn and wheat.  As a young man, my grandfather had part of his colon removed and wound up deciding he felt best if he stuck to eating oat bran.  In the last five years, my brother has had a difficult time and is now excluding corn and wheat

B.D. West Hartford

A: Thank you so much for sharing your story. I should begin by clarifying the difference between food sensitivities and food allergies:

The symptoms of food sensitivity or intolerance may be delayed, mild or we may not experience any symptoms. Food sensitivities, which can lead to inflammation in other parts of the body, have been associated with gastrointestinal disorders, rashes, migraines and chronic conditions like arthritis.

An allergy occurs when the immune system identifies a specific antigen (food, in this case) and produces a specific IgE (Immunoglobulin E antibody. This induces an immediate and acute inflammatory response such as hives, rash and swelling of the tongue or throat.

I would not recommend that you reintroduce foods to your diet that have caused an allergic reaction.

These tests identify the chance that there is a food allergy, but will not identify food sensitivities:

  • Skin-prick tests (SPTs) do not require blood to be drawn, can be read in minutes and identify as many as 40 allergic reactions at one time. It is common for SPTs to produce false positive results. Taking antihistamines could lead to false negative results.
  • Blood tests detect antibodies in your blood that are only produced when your body has been exposed to the allergen. So you would need to ingest the food to have an accurate result. Another thing to keep in mind is that the test is not positive or negative: It is based on a scale interpreted by a trained medical professional to determine the chance that there is an allergic response.

Now let’s talk about food sensitivities and intolerances.  Enzymes produced by the stomach, intestine, pancreas and liver digest food so it can be absorbed and used for energy metabolism. If enzyme production is significantly reduced, we will experience malabsorption symptoms that overlap with celiac disease. For example, insufficient production of lactase (the enzyme that breaks down the lactose or milk sugar) is more common among celiac sufferers and causes bloating, gas, cramping and diarrhea. Fructose malabsorption also seen with celiac disease and should be considered with ongoing symptoms that mimic lactose intolerance.

Recurring diarrhea increases risk for nutrient deficiencies such as: folic acid, zinc, iron, and calcium so it is important to find the root cause to get symptoms under control.

Fructose malabsorption can also cause fatigue, headaches, mood changes, and constipation. The treatment for fructose malabsorption is a low fructose diet. This diet limits foods containing high amounts of fructose and fructans — a form of fructose found in wheat and vegetables. Some examples of foods high in fructose are: apples, pears, peaches, honey, and fruit juice concentrate. You can find detailed lists online.

Your family may also benefit from a low FODMAP diet. (FODMAP is an acronym for the short-chain carbohydrates that are not absorbed adequately by the small intestine: Fermentable, Oligosaccharides, Disaccharides, Monosaccharides And Polyols.) For more information on this topic and to download a free Low FODMAP App for Apple and Android, click here.

I would recommend scheduling an appointment with a registered dietitian who has experience with medical nutrition therapy for gastrointestinal disorders, food allergies and FODMAPs.