Enisyl F is a veterinary Lysine paste Enisyl-F Oral Paste For Cats 100ml - £12.95 - might be worth a try, although like Elmstar said, you can just buy Lysine from the health food store (make sure its just pure Lysine - sometimes they add other stuff in as well) Solgar Lysine is a pretty good brand https://www.yourhealthfoodstore.co.u..._l_lysine.html

i had limited success with lysine with my herpes virus cats, although I think it did help a bit. The usual dosage is 500mg when there is a flare up, down to 250mg as a maintenance dose.

If you do give Lysine a go, don't give the full dose straight away - slowly build up to the full dose over a week or so - just because it can cause a tummy upset if given all in one go initially.