I have been allergic to cow dairy all my life, as well as multiple trees/grass pollens/mold spores. About 8 yrs ago I became incredibly sick with no help offered by my family MD as to why or what. I found an Integrative Medicine doctor who tested me for food allergies, found that I was highly reactive to 16 different foods, most of which I ate regularly. My reactive status was not immediate like when your tongue swells up, or that creates hives, it was long term--meaning that the foods were a toxin that my body was fighting as it would any other inflamatory. Since the food was in my body tissue, my immune system was attacking my own body. The doctor put me on a very restricted medical diet having me avoid each of the 16 different foods, and any food within their "family." The basic rule was that I had to stay away from those foods for 9 months, that included handling those foods. The 9 month period is generally long enough for your body to reset itself, then you can add the foods back into your diet one at a time over a period of 2-3 months for each to see if you have any type of reaction. If no reaction, then you can continue to eat that food in moderation, if any type of reaction, start the 9 month track again with that food. It took over 3 years for me to determine what would and would not work, still cannot do cow dairy, cane/beet sugar or garlic, but she taught me what to use for substitutes and I'm doing well. Throughout the process she had me using multiple supplements and vitamins to build up my system and get me healthy again, it worked. It was a long hard road, but it was much better than being as sick as I was when I first went to her. My husband and I both truly believed that I was going to die, and no one understood why. When I get crazy and ingest some of my offending foods, the eczema returns to my face, I treat with cortizone cream and clean up my diet--works every time.
The point I am making here is that yes, testing for food allergies is real and beneficial--if done by the right person, and ignoring it can be fatal. The test I used is blood, saliva and fecal testing, and there are only two labs that I know of that are certified to do the actual testing, the doctor draws the blood samples, then you have a kit to collect the saliva and feces. The doctor I used was also a licensed nutritionist, so I had a lot of help with the diet and food substitutions. I learned a lot, she gave me websites to do my own research, and I think me being so involved in every step of the process really helped me to stick with the program and truly understand what was going on. Knowledge is power and I am grateful for all the things she taught me. I am now empowered to control my own health. My personal crisis and research proved to me that eczema is an allergic reaction to food. Many do not believe that, I just hope that they never have to live through it to learn.
I hope you get help for your son and that he makes a speedy recovery. Good luck to your family.