Lysine (it's spelled with an s not the phonetic z)is an amino acid that some studies show prevents the herpes virus from growing. [It's often sold as L-Lysine or amino acid K] It's usually used for cold sores. I have never heard of any pain reduction effects.
I started using it about thirty years ago on a doctor's recommendation and whether it was the placebo effect or not, my cold sores disappeared and stayed away.
Lysine also helps the body absorb calcium and decreases the amount of calcium that is lost in urine.
As Christine noted, you should check with your doctors. I quit taking Lysine during my TX. I take it now.
Perhaps your friends who mentioned it have confused it with
oral lysine acetylsalicylate which is a form of aspirin used to treat migraine pain or with Lysine clonixinate, a derivative of nicotinic acid also used to treat pain.
Keep the Faith
Charm