Originally posted by rosethecopycat
There is an ingredient in some L- Lysine that is not good for cats.

Wait... I'll look it up.

Make sure it doesn't have propylene-glycol in it.
Actually propylene glycol is an additive in many foods etc. It's ethylene glycol which is potentially deadly. L-lysine works very well, but has to be used for quite a while before any noticable effects show. Several foster homes use it for their cats, and kittens, and swear by it for cutting back on upper respiratory outbreaks.

http://www.tomsofmaine.com/toms/ifs/...ene_glycol.asp