Benedryl is the only thing you should use. We were told to never use human meds for animals, it could cause serious effects and some are know to be fatal to dogs and cats. My vet told me I could use half and half witch hazel and glycerin for conjunctivitis. If the third eyelid is showing and red it could be that but in any case the witch hazel an glycerin is an eye soother for seed pods in eyes, etc.