Food allergy has become a more commonly discussed disease in the news media in recent years, and there is evidence suggesting that it may be increasing in frequency. Allergies to foods can be quite anxiety provoking for many patients and their families and result in a decreased quality of life. However, there are many misconceptions regarding what an actual true food allergy is.
It is often helpful to first discuss the definition of an adverse food reaction. An adverse food reaction is any type of untoward or abnormal response resulting from the ingestion of a food. Most adverse food reactions are not allergic in nature. Common examples of a non-allergic adverse food reaction include heartburn due to spicy foods and lactose intolerance.
Allergic reactions to foods involve abnormal immune system responses to food proteins. The immune system is constantly surveying our bodies in search for “enemies” such as bacteria and viruses. However, in food allergy, the immune system mistakenly identifies a food protein as an “enemy” and overreacts by producing a large amount of attack signals and chemicals. One of the main immune system players involved in food allergy is a normally produced protein in the body calledImmunoglobulin E, which is abbreviated as IgE. This is the substance that finds the food that it “thinks” is a “bad guy” and tells other cells in the body to attack by releasing strong chemicals. In this process of attacking the presumed “bad guy,” the chemicals, chiefly histamine, also affect the surrounding tissue. This effect is the reaction that occurs when someone with a food allergy ingests a food he or she is allergic to.
Food allergy symptoms related to IgE are rapid in onset, within a few minutes to two hours after ingestion. An allergy to food will also produce a large reaction to even a tiny amount as opposed to a non-allergic adverse reaction, in which a small amount produces only a mild response.
There can be further progression to a severe allergic reaction called anaphylaxis. Anaphylaxis symptoms can include
These signs and symptoms of anaphylaxis can be life-threatening and require emergency medical attention. In young children, 90 percent of IgE-mediated food allergies that can result in anaphylaxis are due to cow’s milk, egg, peanut, tree nuts, soy, wheat, fish and shellfish.
Myths and misconceptions regarding food allergies are quite common. Misconceptions in food allergy are often related to one’s symptoms in addition to testing interpretation. As noted above, food allergies and food intolerances are entirely different. A food intolerance, such as lactose intolerance, will cause mild symptoms like an upset stomach if a small amount is eaten and more symptoms like a worsening upset stomach with diarrhea if a larger amount is eaten. A true food allergy resulting in anaphylaxis will cause a severe reaction even after eating very small amounts. Distinguishing between a food intolerance and a true food allergy is sometimes quite difficult and often requires the expertise of an allergist/immunologist.
This leads us to food allergy testing. Determining whether or not symptoms are due to a possible life-threatening food allergy versus merely a food intolerance can be difficult based upon history alone. Therefore, testing is often performed. The two main types of food allergy testing are skin prick testing and blood testing. Having a clear understanding of the accuracy of these tests is crucial.
A common misconception is that someone can have blood or skin testing to multiple foods to determine what they are allergic to. Unfortunately, it is not quite this simple because the best currently available tests are not 100% accurate. The accuracy of food allergy skin and blood tests are comparable, but the skin test is generally considered a little more sensitive (in other words, a negative skin test is more accurate). Contrary to what one might think, the accuracy of a negative skin or blood test is better than a positive test. Overall, a negative test is correct about 90% of the time, but a positive test is only correct 50% of time. This means that a positive skin or blood test to a food can be wrong half of the time. This also means that a large battery of food testing is generally not indicated.
Given these pitfalls of the currently available food allergy testing methods, your allergist will likely ask many questions regarding the exact nature and timing of the possible food reaction. He or she may then use skin testing only to the specific foods in question to determine the probability of a true food allergy. Because of the inherent inaccuracies of food allergy testing, the best test to rule out a food allergy is an oral graded food challenge to a particular food.
An oral graded food challenge is a method of definitively determining if an allergic or adverse reaction is related to a food. It typically involves beginning with ingestion of minute quantities of the particular food in question and gradually increasing to a full serving. It is performed under close observation, which is usually in an outpatient setting such as found at the offices of Atlanta ENT. The allergist/immunologist will administer this type of procedure. The history regarding the nature, timing and severity of the reaction in addition to the results of the skin prick test and/or blood allergy test will help determine whether an oral graded food challenge should be performed. In many instances, it is performed if the risk is relatively low based upon the information as noted above and is also used to assess possible resolution of a food allergy.
There is no cure for food allergies currently. The only treatment is strict avoidance and therapy with self-injectable epinephrine, which should be carried at all times in food allergic individuals.
There is currently a considerable amount of research in other forms of treatment of food allergies such as oral immunotherapy, which involves slowly increasing daily doses of the particular food to induce tolerance. Several studies have shown some promising results, but details regarding effective doses and timing of doses have not been fully elucidated. Because of these issues, most allergists feel that oral immunotherapy for foods should still be considered investigational and not for clinical use.
The allergists at Atlanta ENT have extensive training in correctly diagnosing food allergy related diseases, properly interpreting food allergy tests, and managing children food allergies appropriately.