Sneezing with a little bit of blood through the nose is a fairly common side effect of a bad upper respiratory infection. When I adopted one of my kitties, he was doing that as well as coughing. Once we got the upper respiratory infection cleared up, he was totally fine. I use L lysine from whole foods. it is 500 mg human strength and pretty pure, vegetarian capsules. One of my other cats is older and has congestion problems at times. I use the lysine if it gets bad but most of the time he can be cleared up just using Jarrow formulas lactoferrin. It's much safer than extended use of L-lucine. Hope this helps