My kitty had been acting strangely. I figured that he might be ill. Details here: http://www.thecatsite.com/t/274131/very-social-cat-hiding-for-no-apparent-reason I found bloody discharge after he sneezed. He is with our vet now. I was doing some research on the forums here. Someone else was asking about bloody sneezes, and was given a link to this article about feline herpes: http://www.vetdepot.com/feline-herpes.html The part cited stated that "cat owners should only use lysine products intended for felines such as Vyralis with L-Lysine. Products formulated for humans may contain propylene glycol as a preservative, which can cause reactions in the blood." I know that the source has every reason to recommend pet products, but it still makes me wonder. About a month ago, I switched from cat lysine to the NOW brand recommended very often on this forum. Could that have anything to do with the bloody sneezing? Has anyone else had trouble with the NOW lysine? It claims 100% purity and does not list propylene glycol (or anything else) as a preservative.