Could be fleas even if not evident. My cat Tika licked her hair off one side almost all the way, as far as she could reach. Tried steroid shots and flea medicine for a couple years. When steroid wore off, she would lick again. Thought allergies at first, tried different foods, went grain free and still no change. Then thought it was stress due to moving and also to getting a younger cat. She started hiding in/under the couch earlier this year, and would only come out to eat and potty. I was blaming the younger cat again who was chasing her and making her a "scaredy-cat." Turns out the flea medicine was doing nothing and she was super-sensitive to fleas and was trying to hide from them, and licking where she could reach because of the irritation from the "invisible" biters. So, I began flea-combing the dog and all cats daily. The fleas are really good at hiding, we had no idea we had a flea problem. Think the dog was picking them up on neighborhood walks. Now we are flea-free and she is out of hiding and her usual self...and no more fur mowing! Side benefit, they all enjoyed the extra attention. Best of luck, hope you find a quick solution for your Samson.
