My first thought was fleas....then allergies...then anal glands....but what do I know?!!?
Our Schnauzer used to do that sporadically - he used to itch his right ear with his right back paw, then lick that paw 'til it almost hurt....then it almost used to spread around the back end of his little body....
I truly think you should get him to your vet, see if they can identify the root cause, else you could be going round in circles....I wish you luck, and hope you can sort it out soon
Sally + Harry
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