One of the fun things about an auto-immune disease is that it is highly individualized. What triggers an arthritic flare for one person may have absolutely no effect on another one. That’s why you almost see websites about arthritis with possible flare triggers (at least about psoriatic arthritis) use also sorts of wiggle language and caveats. Some of the most common I’ve seen include caffeine (no change for me, as evidenced by coffee-free Lents), cheese/dairy (I haven’t really gone full dairy-free, but have no change when I reduce dairy), alcohol (no change here, whether I imbibe or not), sugar (early on I tried this and went added-sugar free for about a month on the theory that sugar, or at least too much sugar, is an inflammatory. No change during, no change when I added sugar back in, no change when I indulge in sweets cravings). So, auto-immune really is a case of “your mileage may vary.”
All that said, I think I’ve run across one thing that usually triggers an arthritis flare for me: lack of sleep/disrupted sleep. As long as I clock about 6-7 hours a night, I’m fine. One or two days of a little less, and things seem OK. Much more than that and I do start to feel pain in my hands. I should note here that although I have a few swollen joints, my particular manifestation of psoriatic arthritis is not usually painful. A twinge now and then is all I usually have. Things look much worse than they actually are (and they don’t look all that bad, really).
Since I was on travel last week, my sleep schedule was completely disrupted. The jet lag from being five hours ahead, along with a couple of later than usual nights, as well as a couple of long plane trips conspired to give me a flare up part of the way through the trip, and that I’m still trying to tamp back down. The main thing is getting back to usual amounts of sleep so as not to make things worse. Secondarily, I’ll take a minimal dose of an anti-inflammatory if the flare continues more than a few days, so as not to cause damage to the joints. This usually gets things back under control after a couple of days.
Again, what works for one auto-immune patient might not (probably won’t) work for another. This happens to be what sets things off for me, and one way I’ve come up with to handle it. As with most things in life, your mileage may vary.