We have a sheltie that was licking his foot constantly. No sign of any trauma and not favouring the foot when walking. We were told about a product called Get Up and Go and tried it and it worked. He has totally stopped the licking and chewing.
Supposition is that he may have had the equivelant of gout or arthritis starting up in the joints. Get up and Go is distributed by Absolute Pet Nutrition Pty Ltd., phone no. 1800338822 and web site www.getupandgodog.com.au ( I have no financial interest in this company - just sharing).