Benadryl is the best thing I have found for allergic reactions. (The last time I ate Brazil nuts my lips swelled up to twice their normal size and Benadryl quickly reduced the swelling/itching.) Of course, you should rush him to the hospital for a shot of epinephrine if his throat ever begins to swell. And it wouldn't be a bad idea to keep an epi pen on hand just to be on the safe side. The epinephrine/epi pens are available only by prescription so your doctor will determine whether or not your son needs one. I hope this information helps.