I don't know ... I do not swish it myself, but have heard of others who do so. I also am aware that sodium chlorite in solution is available commercially for oral hygiene, but that is very likely at a lower ppm.
If it bothered you topically in your mouth, then maybe you should only swish it at a lower dosage.
Was there any lingering after-effect to the "burn", or was it only while you were swishing?