Need some links on what this thing is. Suggest trying to find what the active ingredient is

Icy hot is an analgesic. It reduces the pain that the user is feeling. The theory is pretty simple. Pain comes to your brain on a certain type of fiber (nerve). The feeling of hot and cold comes into your brain/ spinal cord on a different type of fiber (nerve). The hot and cold nerve when stimulated synapses on the pain nerve and prevents the pain information from getting to your brain. Therefore, you don't feel any pain. I hope this helps.