to foods would likely not cause this type of reaction but rather rashes, diarrhea
, etc. It is more likely due to carbohydrate intolerance: lactose, fructose, and/or sorbitol (really an alcohol but used as a flavor enhancer, especially in diet foods) The problem is that when the intestinal mucosa cannot absorb a substance, enzymes are necessary to break them down, particularly with complex sugars like lactose and fructose (fruit sugar). When they cannot be broken down with the enzymes, either because of a lack of that enzyme (lactose intolerance is quite common) then bacteria begin to attack the substance and the result is fermentation (just as with beer) and gas and odor production. Lactose intolerance is very common after the first year of life, especially in populations of Asian or African heritage where they historically never had a dairy industry and thus only drink milk until weaned from the breast, as with every other mammal.
The first thing I would do is eliminate lactose since avoiding dairy products is pretty simple. This includes not just milk but cheese, yogurt, ice cream, pudding, etc. but not foods cooked with a little milk. Do this for a couple of weeks to test the effect and then move on to fructose and finally sorbitol, which you will be surprised to see in many foods for their sweetener effects as so many foods eliminate sugar.
I'm sure eventually you will figure out the offending substance and be able to get him through this.
Edited by Dr. A. Clark on 1/29/2010 at 12:31 AM EST