Those bumps that only show up in angled light are tricky - the coat can hide them indoors. A photo taken in that same sunlight is actually really useful to bring along, since subtle bumps often flatten or fade in the exam room.
Since the allergy approach hasn't made a difference, a recheck may be worthwhile rather than assuming seasonal allergies are the cause. A few other things can produce small raised bumps like that - irritation from something he contacts on walks, parasites, or inflammation around the hair follicles - and each needs different treatment than allergies.
Some details your vet will likely want: how long the bumps have been there, whether individual bumps come and go (hives often appear and fade within hours, sometimes right after walks), whether he seems itchy, and what the skin looks like when you part the hair - redness, scabs, pimples, flakes or hair loss each point in a different direction. If no skin scraping or cytology has been done yet, asking about those is reasonable too.
One caution worth knowing: if bumps ever come with facial swelling or any change in his breathing, that is an emergency-vet situation rather than wait-and-see.