We see many patients, especially children and infants, with problems related to foods that they eat. Not all such problems are food allergies. Intolerance of one sort or another to foods is actually more common than allergic reactions to foods. To reach a diagnosis and create treatment plans for all adverse reactions to foods we use a combination of clinical history, related medical problems, family history, skin and blood tests, oral challenges performed under supervision in our office, and structured elimination diets.
Food allergies involve an arm of your immune system that makes a type of antibody, named IgE, that attaches itself to one specific substance, called an allergen, to which you are allergic. When we say specific, we mean it. An IgE antibody specific for peanut does not recognize or attach itself to egg or walnut or any substance other than peanut. Of course, you can have other IgE antibodies specific for other allergens like other foods, pollens, animal danders even the venom of honeybee stings. Compared to other antibodies found in your body you make very little IgE, yet it packs a big immunological punch. The other end of IgE antibodies make strong attachments to mast cells via special receptors on their surface. All mast cells do is synthesize histamine and other biochemical substances designed to begin, enhance and prolong allergic reactions.
When an allergen comes along that is recognized by the specific IgE attached to a mast cell, the combination of allergen and IgE work like the ignition switch on the motor of the mast cell. Turning on mast cells starts a reaction that releases histamine and many other mediators. These mediators interact with small blood vessels, nerve cells that when triggered give the sensation of itching, and other immune system cell. It’s important to realize that the action of the mast cell is always the same regardless of the allergen that turns the cell on. The difference in allergic reactions from allergic rhinitis to allergic asthma to hives to food-triggered vomiting and anaphylaxis is based upon the number of mast cells turned on and their location in your body.
Food allergies also play a role in eczema and in eosinophilic esophagitis.
Food intolerance does not involve IgE antibodies and are never life-threatening but may make you feel unwell. They occur for a variety of reasons such as a decreased ability to digest a food (lactose intolerance) or the presence of substances in the food having drug effects (caffeinated drinks, tea, chocolate). There are few dependable skin or blood tests for diagnosing food intolerances. The diagnosis depends on history, physical examination, and what happens when the food is removed or added back into the diet.
Some foods cause both allergic and non-allergic reactions. Two such foods are cow’s milk and wheat. Both can cause allergic reactions like hives and vomiting. Both can cause life-threatening anaphylaxis. Cow’s milk and dairy products can also trigger bloating, upset stomach, cramps, gas and diarrhea if you have an absent or limited ability to digest lactose, the sugar found in all milk. Gluten, a protein present in wheat, may trigger a type of immune reaction in the small intestine different from an allergic one, resulting in a condition called celiac disease or gluten enteropathy. The symptoms of celiac disease are cramping, bloating, and diarrhea. If foods containing gluten (wheat, oat, barley) are not removed from the diet of a person with celiac disease injury can occur to the intestine leading to the inability to absorb nutrients and resulting in dangerous levels of weight loss.
The diagnosis of food allergy or food intolerance are sometimes simple but are often complicated. We can help sort these issues out for you.