Both of my cats are FIV+, which much like HIV, means that their immune systems are suppressed. I have used this lysine supplement consistently for several years by mixing it in with their soft food every morning and every night. They are picky eaters as far as supplements go, but they like the flavor of this one. I happy to say that both of my cats are in great health, at roughly 9 years old, they are doing remarkably well for their diagnosis. One of my cats also has herpes, which has given him a nasty crusty eye infection in the past, but ever since using this product he has yet to have another outbreak. I highly recommend this for immune compromised cats!