I don't know... I drink a lot of diet coke and I always have. You need arginine and lysine in your diet; I'm not suggesting arginine is bad. If what some of have is viral in nature, we want to avoid supplemental arginine to maximize the potential effect of L-lysine supplements. I don't think the amino acid relationship causes the condition. It merely encourages or discourages viral replication once the virus is active. That is likely related to the strength of the immune system.
You want your overall diet to remain healthy and balanced.