My Dog Swallowed A Lot Of His Own Hair When Pulling At A Burr. Now He's Salivating A Lot And Will Not Drink At All Although He Ate A Little Fish. Will This Right Itself?

He's been quite poorly all day - very quiet which is not normal for a 4 year old Border Collie. He pulled out and must have swallowed almost all the end of his tail because we can now see the bony bit. We got all the other burrs out of his coat but didn't notice that he must have had some in his tail end.