I have a couple of formulas that can sometimes be useful for Herpes cases but it may be difficult to get a cat to take either with any regularity. Cats can be pretty difficult to get herbs into.
These are the formulas.
INFXN-HRPEZE – 
Immunity Support : 
You can also give Lysine which really helps to inhibit the herpes virus. It’s just an amino acid and is perfectly safe. You can usually buy it where vitamins are sold.
Herb formula dosing can be found on any of the product pages “more Info” tab.
Don't use herbs or combine herbs with medications or use them during lactation or pregnancy without talking with your healthcare provider.