Please see this:
https://www.scientificamerican.com/article/you-smell-sick-detecting-illness-by-scent/
I, too, have noticed the “back showing” of others, even when with friends. My prime example was being slowly squeezed out when playing a game at a round table. I ended up playing as a satellite in my own orbit! I mentioned this to my flatmate the next day. She denied that this had happened, and that this could ever possibly happen. We were all decent, caring, friendly people after all …
Further, and I can only admit this in my old age (when it’s totally useless?), I am quite a handsome man. Either something like the mechanism mentioned in the Scientific American article is occurring or a lot of short-sighted women are not wearing their glasses.
And, of course, it’s possible that ADHD people lack the sickness smelling ability. Anxiety could well develop in such a world. Although that doesn’t explain my need to “run away, run away” (that’s a quote from a Monty Python film.) Unless I smell non-ADHDers as the sick ones!