I agree with lots of the posts you've already recieved - something he is eating is not agreeing with him. Probiotics may help - I take a powder (New Chapter's All Flora but there are MANY brands - personally I take 1/4 t mixed in with a small glass of water daily).
I used to let out stink bombs, too - turns out it was wheat! I was allergic and could not digest it. When I cut out the wheat, no more stinky gas! The beano may help but it would be better if he figured out what was CAUSING the gas in the first place.
Smelly gas is not normal for anyone - it is a sign of digestive problems.
Something else that might help is baking soda - instructions are on the side of the package (I tried that once, but it tastes gross).. I much prefer the probiotics - they help the gut from the inside out! Yogurt daily might help as might Kefir and other fermented products.
BTW, not all doctors are trained in nutrition...
Good Luck!
E.