Please consider removing all chemicals from his diet. Eat organic whenever possible, and stick with foods in their most natural states...that is, not processed foods. This can be a challenge if you are accustomed the All American diet, but it can literally change his, yours, and your husband's lives. Try it for one month and see what happens.
In addtion, I would also remove the most popular allergenic foods from his diet. (Wheat and other gluten grains, dairy, chocolate, peanuts, corn) Also sugar and ALL dyes.
What to eat? Veggies, fruit, some meat and non-gluten grains. (Quinoa, buckwheat, millet, teff, rice)
Think of it as a journey the three of you are going to go on. Even pick an itinerary (for fun) and make this a fun adventure. Explore restaurants that can cater to your diet.
Then, after one month, slowly, s-l-o-w-l-y, add one food back week after week, watching for any reactions.
There are herbals you could use to strengthen and tonify the body, too.
I think you might be amazed and grateful at the results you experience. Enjoy the process! You also might hum to and with your son....it is simple, and can help the brain "reset." How much better all this is than going the prescription route, which only masks the problem and creates others.