Upset stomach

My male 2 y/o beagle has an issue where as soon as he gets nauseous ( not sure why, no human food and wears basket muzzle on walks to prevent picking anything up) he compulsively licks everything. The floor, walls, furniture etc. I have to put him in his crate until it passes ( even if he vomits, he still exhibits this behavior). Can last up to 4 hours. All my vet says is give benadryl and wait for it to pass. Anyone else deal with this or have suggestions?? Help!