my big boxer, 3 yrs, scratches 24 hoursday. Vet has given several meds for allergy. No result. I brush him down every day when he whines for relief. He has two hot spots now encrusted over, grey colour, on his otherwise gleaming and handsome back. Already changed his food brand several times. Nada. His snuffling, slobbering desperate attempts trying to get at hard-to-reach parts all night has us in a tizzy. Advice please.