Inspired by one of our favorite television shows, Allergy Myth Busters looks at a number of popularly held beliefs about allergy. But are these myths just urban legends or are they true?
IgG RAST testing is an effective means to identify food allergies.
What does science say?
It is estimated that 15 million people in the United States have food allergies. This includes up to 1 in 13 children. Therefore, appropriate evaluation and treatment of these allergies are essential. Various methods have been described to test for food allergies since the 1970s. These include skin prick testing to possible offending foods, ImmunoCAP IgE blood testing, and IgG RAST blood testing.
So is the myth busted or true?
Detection of IgG antibodies has been discredited as a reliable diagnostic tool since the 1980s. Unlike IgE antibodies, which are responsible for allergies, IgG antibodies can be found in allergic and non-allergic people regardless of whether they are healthy or sick. IgG antibodies are the normal antibodies made by the body to fight off infections. Increase in levels of IgG antibodies present in the circulating blood is thought to be a normal response to the ingestion of food. In fact, IgG antibodies have actually been found to go up during successful research studies on food immunotherapy. Also, allergy testing to foods using IgG RAST testing has been shown to lack clinical relevance. These tests are not validated and lack sufficient quality control.
These unproven tests may lead to false diagnoses, increased anxiety, and a useless strict avoidance diet. If a food allergy is suspected, evaluation, diagnosis, and treatment should be performed by a board certified allergist. The evaluation should include a thorough medical history and a physical exam. The allergist may perform tests including skin prick tests and ImmunoCAP IgE blood tests to help identify a food allergy. Both methods are highly sensitive and useful to help exclude a diagnosis of food allergy. An oral food challenge or even a trial elimination diet may be necessary. These tests have all been proven to be effective diagnostic methods which the board certified allergist may use in conjunction with the information from the clinical history and physical to provide a diagnosis of a food allergy.