@jason30 - I used to have a detox reaction to many different things - anything that had "cleansing" properties would cause me to detox: I would get tired, feel fluish/sick, digestion would be off, feel spacy. I don't know if this was MCS but it was very real. I was probably detoxing from something at least half of the time. A 20 minute treatment in a far infrared sauna left me feeling sick for 3 days. I think I was retoxing- toxins would get released from cells due to something I'd ingested or been exposed to, and the toxins would just circulate and get redeposited.
About 4 years ago I started taking glycine for sleep. I reacted extremely strongly to glycine - it hit me like a truck, it knocked me out and when I got up the next day I felt like I'd been hit by a truck, very strong detox reaction. I was also very spacey, got lost going to my sister's house. I would have stopped it, except muscle testing indicated it was good for me but in a very small dose.
So I started taking a very small dose and over a period of 6 months increased it very gradually, as my tolerance for it increased and by the end of 6 months I was no longer reacting to it. And, I was no longer reacting to the all the other things I used to react to - apple cider vinegar, cayenne, there so many things that made me feel sick, I've lost track. I believe the glycine got my detox pathways working properly. I also started inositol and glutamine around the same time and had much smaller detox reactions but still, they did cause me to detox, and this article lists all 3 of these as being necessary for Phase II liver detox:
https://www.diagnose-me.com/treatment/liver-detoxification-phase-II-suppor, t.php And by the end of the 6 months I no longer reacted to them either.
I've only had one detox reaction since that time, when I got a new vinyl floor in my bathroom, but that only lasted a couple of days.
So I don't know if this has any bearing on MCS. It might - also B1 has helped me a lot so I hope you're eventually able to take it again. Also, when I first started B1, it gave me a noticeable boost in energy followed by severe fatigue - turned out it was increasing my need for phosphorous and thus depleting it (hypophosphatemia, hallmark of refeeding syndrome), which is another story. When I fixed the low phosphorous, the severe fatigue went away, but I continue to have to supplement with it.