I never let myself run out of this product and recommend it to others with multi-cat homes, especially if Herpes Simplex is present. I have seen it support immune systems for cats with FIV as well. I have indoor and outdoor cats (all cats are spayed and neutered and outdoor cats are being integrated into house). Since using this product, after my vet recommended adding Lysine to their diet, respiratory problems associated with these viruses were virtually eliminated. Runny eyes, congestion, etc., are a rarity and fleeting when presented. The quality and price helps responsible pets owners provide the contentment and health the needs of all their pets. Additionally, VetDepot is reliable in their stock status and shipping.