Methyl salicylate
"I placed Icy Hot Vanishing Scent Gel Pain Relieving Gel (as on the tube) on the inside of my knee generously as per directions, but not much at all four hours later a small amount. About thirty minutes after the second application I became very nauseated for hours and felt if I was going to have diahrea.  At this time. I still hours later feel no better. I did however wash it off as soon as I read the side effects."