How can I tell if my dog has an allergy?

How can I tell if my dog has an allergy?

Bernadine D. Cruz. DVM (Companion Animal Medicine Expert, Laguna Hills Animal Hospital ) gives expert video advice on: What is the best way to transport my injured dog to the vet?; What medical supplies should I keep at home for my dog?; What do I do if my dog swallows poison? and more...