The first bottle I used, I didn't notice a burning sensation until I was sweating on the bike and my pores were open. HOWEVER,
The second bottle I bought came in a different bottle and seems like a newer formula. I feel a burning sensation a minute or two after applying it, and yesterday, I felt like a hole was being burned through my skin during cardio. I had to stop after 20 minutes, I couldn't take it anymore. The entire drive home I was pouring cold water onto my stomach every 30 seconds to ease the pain. It was as close to unbearable as you can get. I was going crazy, it hurt SO badly.
Not too sure if this is a good thing or not, but it sure as fuck works.