“IgG and IgG subclass antibody tests for food allergy do not have clinical relevance, are not validated, lack sufficient quality control, and should not be performed. “–AAAAI/ACAAI Allergy Diagnostic Testing Practice Parameter
I saw a very nice young man today who was brought in by his mother for some advice on food allergies. He had been having headaches, and his primary M.D. had ordered a large panel of blood tests which, he told the family, indicated a number of food allergies. Mom was looking for advice on how to proceed with avoiding 36 different foods. The answer was easy: her son didn’t have to avoid any of the foods because the tests didn’t have anything to do with food allergies. To her credit, she handled the news much better than I would have if I’d just been told I’d spent $1500 on bogus allergy tests.
By way of brief explanation and without getting too technical, the immune system makes four different types of antibodies, proteins which help fight off infection. They are called IgG, IgA, IgM, and IgE and they all have different functions. IgG is the primary antibody in the bloodstream and helps fight bacteria and viruses. IgE is the allergy antibody so when you do a blood test looking for allergies, you measure IgE not IgG. The quote at the top of the article is from the most recent allergy practice parameter and it doesn’t mince words: IgG tests for allergies are bunk.
Back to the case at hand. I really felt bad for the mom. She was just trying to take good care of her child and she was given really bad information by a physician she trusted. Her son was just happy that he could go back to drinking milk.
It’s a shame that this stuff is allowed to be peddled as legitimate medicine, but there’s not much that can be done about it. It really highlights the level of trust and vulnerability a patient has with his or her physician. There’s no way a layperson should be expected to have enough understanding of allergy and immunology to distinguish between legitimate medicine and quackery. So what can a patient do? Look for the words after your doctor’s name: Board Certified in Allergy and Immunology. If you want an allergy test, go to an allergist.