Have you ever wondered why alcohol makes a cut hurt? Other liquid substances, like water, don't cause pain when applied to cuts. The answer lies in the lowering of VR1 receptors. VR1 receptors are a special kind of cell in your skin that respond to heat.
Studies have shown that ethanol--which is a kind of alcohol--causes skin cells to put out the same neurochemical signals they put out when heat is around. The result is that it doesn't take as much actual heat for the VR1's to turn on. Researchers have found that alcohol lowers the amount of heat needed to turn on VR1 receptors by almost ten degrees.
It isn't known for sure yet, but researchers think that ethanol may lower the threshold so much around inflamed tissue that your own body temperature kicks off the VR1 receptors. Not only does the cut hurt, but it now feels like its on fire as well.