Rereading, I would replace “not that common” with “not that likely”.
Everyone has some fungus. And yes, it can flare up. But to the extent of being the source of illness, IMO, not likely.
My new primary doctor questioned me about candida, which in itself was shocking. It once again raised suspicion, but testing showed nothing.
Years ago, I had a couple different alternative practitioners diagnosis me as having a candida overgrowth. Anti fungals, enough herbs, cleanses, and supplements to kill a cow. Nothing, absolutely no improvement.
I’ve since met someone with systemic candida, and although the man was very sick, his symptoms had few things in common with ME/CFS. He was in his mid 60’s, owned an HVAC business, and was still able to work daily. He had few to no digestive problems. He was very thin and had lost a lot of weight, but could still run circles around me.
I’m sure someone will tell me I don’t know what I’m talking about (and they would be correct). All I can speak to is where I’ve been and what I’ve seen. If someone with ME/CFS has found an improvement from treating candida, I’m sincerely happy for you. And yes, I am bitter over the amount of time, money and effort that was put into nothing. Which is prompting me to write all this here.
My best advice is, if someone truly suspects a hidden candida overgrowth, get tested before you take a bunch of meds or spend a lot of money.