if it is a reaction to the shot you can give benedryl. my vet said one 25mg pill per 20 lbs. i am not sure about how long an allergic reaction lasts or if it just continues to worsen. lots of times the eyes and mouth will swell which is not good as it indicates the tongue and esophagus is possibly swelling.
dont feel too confident with frontline. at the grooming shop where i work, about 80% of the dogs that is on frontline has fleas or ends up getting flea reinfestation after 2-3 weeks. frontline is just not completely effective not is advantage.
hope this info helps

shellie~