Hi @senseicat sorry I don't check my mentions often, it sounds like he has either having a flareup of existing latent herpes due to stress or he has gotten herpes from the new kitten and that can take a very long time to clear. Research has not shown that lysine definitely helps but the dose should be 500mg per day, not just a dab. Lysine didn't help my cat much, I recommend that you discuss putting them on Famciclovir with your vet