There's a reason why your veterinarian gives your dog vaccinations in certain locations on his body. She's following the American Animal Hospital Association's guidelines for core and non-core canine vaccination sites. If your dog experiences a reaction at one of these injection sites, your vet will know which vaccination caused the problem.
Canine core vaccinations consists of rabies and the combination vaccine for distemper, adenovirus, parainfluenza and parvovirus. Dogs receive the rabies injection on the right rear leg and receive the combination vaccine on the right front leg.
Your vet might recommend that your dog receive certain non-core vaccines if a particular disease is prevalent in your region or if your dog is at high risk of contracting it. Dogs receive the leptospirosis vaccine in the left rear leg and the Lyme disease vaccine in the left front leg. The vaccine for canine influenza virus, approved in 2009, is also given in the left front leg, but not in the same place as the Lyme vaccine. If you frequently board your dog, he'll almost certainly require a bordetella vaccine. While the majority of bordetella inoculations are given intranasally, if you chose the injection route, the left elbow is the vaccination site.