You could have a sensitivity to cinnamon or mint, inform your dentist of the occurrences to make sure it is nothing else.
There called gum tissue ulcers. I experienced this same problem. My dentist recommended Sensodyne with Fluoride Fresh Mint. No Whitening... I don't have the problem anymore.
However, I used Arm and Hammer for sensitive teeth, and whitening. It didn't cause any problems.
I haven't had any problems with mint or cinnamon in toothpaste, or in general. These were isolated instances of it happening. I've used Crest before, and I currently use other kinds of Senodyne-F without any problems.
I would prefer to keep on using Sensodyne-F, since I have sensitive teeth, and my dentist recommended it for me (and it has helped a great deal). But, my teeth aren't white, and I would love to help fix that with brushing. So, I would like to know the main common ingredients to both the Sensodyne and the Crest whatever Cinnamon Whitening toothpastes. And what is so different in the Arm and Hammer sensitive whitening toothpaste?