How can I be allergic to one dog but not another?

My 5year old old dog hates this one dog. how can i put an end to it?

• my dog was fine with this other dog until we got a puppy and we were outside, other dog was also, puppy was sniffing other dog where he didn't like & snapped at puppy, big dog went charging after other dog. ever since then he wants to fight that dog, the other day in the stair well they met, big dog got out of harness and they fought

• Answer:

  It sounds like your dog is protective of the new puppy. If you know the owners of the other dog, maybe you could try re-introducing the two dogs w/out the puppy present. Before you try this, make sure that your dog sees you as the pack leader, the Alpha. Also do the same for the other owner. If neither dogs sees it's owner as the Alpha, you will continue to have a train wreck every time you try to re-introduce them. However, if you can get your older dog and the other dog re-introduced and under control, you can then introduce the puppy to the other dog, w/out your dog present. Once each of your dogs are trained around the other dog -separately at first, then you can try to re-introduce them all together. You might have to wait until the puppy is a bit older and your dog doesn't feel so protective. Depends on many things. Hope this helps.