Rx Vitamins' immune support for pets is the hypo-allergenic defense system that dogs and cats need to stay healthy and strong in three ways. First, ara-6 is an antioxidant that works to Counter the Effects of stress and the aging process. It also fights free radicals created by toxic cleaning supplies‚ which pets are exposed to for longer and at a much closer range than humans are. Second, shiitake mushroom extract naturally protects nerve tissues and helps improve brain functioning. Third, lutein is a fruit and vegetable Pigment that helps rebuild bones and muscles‚ keeping your pets feeling younger and more active for a longer period of time.