[Tinal]

Hello everyone all though I do not need information on my Yorkie Pebbles, I am having trouble with Calvin my Lhasa. Knowing lots of you have other breeds of dogs as well I thought maybe someone would have some advise for me. Yesterday evening I found an irritated spot below is ear. I had a friend say that it was a hot spot. I have looked on line and have done a lot of reading but just thought maybe someone else has experienced this. Reading on line his diet is just what he needs it has no grain in it and I even give them filtered water. So I have eliminated his diet as the problem. I have never cut his fur other than around his nose and eyes but he still has a full long coat could this be the problem?
I would be grateful for any advise thanks, worried Mommy here!