A food allergy is an immune system response to a food that the body mistakenly believes is harmful. Once the immune system decides that a particular food is harmful, it creates specific antibodies to it. The next time the individual eats that food, the immune system releases massive amounts of chemicals, including histamine, to protect the body. These chemicals trigger a cascade of allergic symptoms that can affect the respiratory system, gastrointestinal tract, skin, and/or cardiovascular system. Scientists estimate that approximately 12 million Americans suffer from food allergies.
Symptoms may include one or more of the following: a tingling sensation in the mouth, swelling of the tongue and the throat, difficulty breathing, hives, vomiting, abdominal cramps, diarrhea, drop in blood pressure, loss of consciousness, and even death. Symptoms typically appear within minutes to two hours after the person has eaten the food to which he or she is allergic.
Strict avoidance of the allergy-causing food is the only way to avoid a reaction. Reading ingredient labels for all foods is the key to avoiding a reaction. If a product doesn’t have a label, individuals with a food allergy should not eat that food. If you have any doubt whether a food is safe, call the manufacturer for more information.
Currently, there are no medications that cure food allergies. Strict avoidance is the only way to prevent a reaction. Many people outgrow their food allergies, although peanut, tree nuts, fish, and shellfish are often considered lifelong allergies. Research is being done in this area, and advances are being made.
Removing a food from your diet can leave you with an unbalanced diet, which may cause other health problems. Seek a doctor’s assistance before making significant changes in your diet.
Epinephrine, also called adrenaline, is the medication of choice for controlling a severe reaction. It is available by prescription as a self-injectable device (EpiPen® or Twinject®).
Many people think the terms food allergy and food intolerancemean the same thing; however, they do not. A food intolerance is an adverse food-induced reaction that does not involve the immune system. Lactose intolerance is one example of a food intolerance. A person with lactose intolerance lacks an enzyme that is needed to digest milk sugar. When the person eats milk products, symptoms such as gas, bloating, and abdominal pain may occur.
A food allergy occurs when the immune system reacts to a certain food. The most common form of an immune system reaction occurs when the body creates immunoglobulin E (IgE) antibodies to the food. When these IgE antibodies react with the food, histamine and other chemicals (called “mediators”) are released, causing hives, asthma, or other symptoms of an allergic reaction.For one to two weeks, keep a food diary of everything you eat, the symptoms you experience, and how long after eating the symptoms occur. This information, combined with a physical examination and lab tests, will help the doctor determine which food, if any, is causing your symptoms.
The skin prick test or a blood test, such as the RAST (or radioallergosorbent test), is commonly used to begin to determine if an allergy exists. (The RAST is sometimes called the CAP-RAST or ImmunoCap test.)
A skin prick test is usually cheaper and can be done in the doctor’s office. The doctor places a drop of the substance being tested on the patient’s forearm or back and pricks the skin with a needle, allowing a tiny amount to enter the skin. If the patient is allergic to the substance, a wheal (mosquito bite-like bump) will form at the site within about 15 minutes.
A RAST test requires a blood sample. The sample is sent to a medical laboratory, where tests are done with specific foods to determine whether the patient has IgE antibodies to that food. The results are usually received within one week.
Although both tests are reliable, there are instances where one is better than the other. Many doctors use a RAST for young children or for patients who have eczema or other skin problems that would make if difficult to read the results of a prick skin test. The results of either test are combined with other information, such as a history of symptoms and a food challenge, to determine whether a food allergy exists.