Thank you for your long and informative response. :-)
I think I may have figured out the problem, at least with me. I had tried oil pulling years ago, back to 2004, and had been following the suggestions of Andreas Moritz . I don't have his ebook in front of me now, but I was doing it for much shorter periods of time, like 2 or 3 minutes. I tried that again a few days ago, and I felt a light soreness to my tongue afterwards, as if a sore was about to emerge.
The past couple of days, I have done 20 minute pulls, and so far I have been fine.
If I had to guess, shorter pulls may be problematic for some people, sort of like getting a detox reaction going, but not fully draining it off.
Hopefully, this is the issue, and I can continue to do this. No major effects so far, except that my teeth are really clean, and I maybe have a little more energy. I never got this from the shorter pulls, not even when I would do as many as 4 consecutive shorter pulls.
If all goes well, I will use a drop of Oil of Oregano in the future. I had very positive results with Raindrop Therapy, so I'm guessing this will also be beneficial.