If you're experiencing swollen nasal passages, bug bite reactions or itchiness, you might take an over-the-counter product called Tavist-D. While that's the brand name, the actual drug is known as clemastine, and veterinarians also use it on their canine patients for many of the same ailments affecting people. While you can purchase the product over-the-counter, don't give it to your dog without veterinary approval.
Clemastine for Dogs
Clemastine works as an antihistamine, reducing the inflammation caused by the histamine compound. In dogs, it's used most often to relieve severe itchiness caused by an allergic reaction. Clemastine side effects tend to be mild. The drug can cause drowsiness in dogs, along with excessive water drinking. Dogs with heart or urinary tract issues, or glaucoma shouldn't receive clemastine. If your dog is scheduled to undergo allergy testing to uncover the source of his reaction, stop giving him clemastine at least four days before the test.