Back Off!

• If your dog keeps his tail high and stiff when he refuses to let another dog sniff him, he's probably saying, "Hey, don't be so pushy." Watch both dogs carefully for signals of aggression and be ready to intervene. Distract your dog for a time-out until they both calm down
  
  

Help!

• If your dog turns away from the other dog with his tail between his legs, whines and tries to hide behind you, he's afraid. Fear can turn to aggression if your dog becomes too stressed, so take him away from the other dog.
  
  

Uncle!

• If your dog tucks his tail and turns his head or body away from the other dog, he's saying, "I give up -- you win." He may also yawn or lie down, using calming signals in submission to the other dog's dominance. If the other dog relaxes too, your dog may then allow sniffing once he feels he will not be attacked.
  
  

Not Tonight!

• If a female is in heat and a male tries to sniff her, she may reject him because she's not ready to mate yet. Bring them together tomorrow and she may be more receptive.