Your SIL is on a very good track.
I am 55 years old, and for over 30 years, my best friend's sister, who is an Integrative M.D., suggested that I avoid dairy, wheat, and sugar to decrease my allergic reactions to other things. That's the key ~ it's not a matter of being allergic to dairy or wheat, it's a matter of those foods compounding the allergic reactions to other allergens. I finally listened to "Dr. Sandy" (as we call her) last February when I was extremely ill and unable to get relief any other way. Within a week of following her diet advice, all of my symptoms began to improve. Now that I have been following this diet for 10 months, I can tell you that my allergies are almost non existent, and all of my chronic pain issues (fibromyalgia, arthritis, and chronic migraines) have decreased to a point of almost not existing. I could have felt this good for 30 years, but I didn't believe Dr. Sandy's advice was legitimate!
Dr. Sandy began her medical career as a pediatrician who specialized in treating children with behavioral and developmental disabilities. She became concerned with the amount of chemical medication that was recommended in the traditional medical treatment of those children, so she began to do research about alternative methods of treatment. As she began putting her new knowledge into practice with her patients, she saw wonderful results, and most of her patients were able to discontinue ~ or at least cut back on ~ their medications. Because she is an M.D., she supports any medical treatment the patient is receiving from other medical sources, and she is always willing to work with the other doctors to ensure the best possible life for the patient.
Dr. Sandy is in Columbus, near Scioto Country Club. I checked your profile to see where you're located, and I see you're not far at all. It would be well worth the drive to have your son see Sandy to see what she would recommend for your son. I promise that if you follow her advice, you will see a dramatic improvement without the use of medication. If he still requires the meds, she will tailor the program accordingly.
I can also send you a file that describes the basic outline for the Dr. Sandy Diet if you're interested. It also contains suggestions for dairy alternatives (believe me, I was the original Dairy Queen! The Wheat and Crackers champion of the universe, and I don't miss them at all now!) Still, since there are genuine medical issues at work here, it would be best to see Sandy yourself. If you send me a private message, I'll be glad to reply with her address and phone number.
I wish you and your son luck, and a healthy, allergy-free life!