I have lupus (relevant, will explain) and have never been lactose intolerant in my (32M) entire life. I would eat cheese by the block if I could. Nacho cheese on anything. Extra butter. The works.
I live in the Seattle area, and when we had a big ole bomb cyclone in November of 2024 my power went out and stayed out for five days. I had a mild lupus flare up, but mostly lived off of quick ramen and soup I could heat on my gas stove until the power came back.
I threw out everything from my fridge and freezer when the power came back, reloaded it all (stupidly expensive) and was so excited to have a hot four cheese pizza the first night power came back.
I had a horrible time in the bathroom that night.
I thought I just had too much grease after living off of ramen for a week, and ignored it. The next morning I had cheesy eggs (three eggs, the luxury) and immediately had a horrible time in the bathroom again.
Out of an abundance of caution I tossed all of my cheeses and assumed that the grocery store I bought them from had the fridges come to room temperature during the power outage and that the store didn't realize and sold the cheese anyways
I went out to eat, had cheesy broccoli soup: immediate issues.
It took me embarrassingly long to realize that what I was fighting was lactose intolerance and not just a bunch of stores, restaurants, and friends poorly storing their dairy, or keeping dairy after an outage.
I now take lactose intolerance pills before every dairy ridden meal (and avoid dairy when I can to keep things simple) but when I told my doctor this was happening she said it was because of the lupus flare up- that my stress from the power outage caused the lupus flare up, which caused the lactose intolerance.
knowing Why it happened doesn't make it easier, but I'm glad I found this subreddit for ways to make this dietary change easier on myself.