As for many chronic illness sufferers, there are plenty of foods I can't have. Clinically speaking, CFS added dairy and casein intolerances to my life. I've learned of other things to avoid through experience.
This makes eating anywhere a challenge, as you can ask all the questions you please; you never know which answers are right, or which questions you're forgetting to ask.
Fast food is pretty risky. Not as bad as it probably was a few years ago, but pretty risky. Some places, you can order quite a bit with certainty (Burger King is fairly good and I was blown away by how knowledgeable the staff at Arby's was). But the same things (fries) aren't safe everywhere.
I remember reading early on in my dairy-intolerant life (less than two years long so far) about a McDonalds dairy conspiracy, whereby they insisted for years that there was no dairy in their fries. It wasn't until enough ER visits among patients stacked up that someone decided to prove that there was dairy present in the fries. From what I recall, McDonalds admitted to the dairy after that. What I may have projected into the story was that they stopped using it.
Tonight, after previously eating fries from McDonalds but not blaming my resulting nausea on them, I decided to ask when I ordered if there was dairy in them.
The teenager's voice in her answer was too funny (incredulous and baffled) to be offensive. "Dairy? In the FRIES? Uh, no!" After my, "OK, thanks. Are you absolutely sure?" her "Yes definitely," was not as solid as the first round.
When I pulled up to pay, I inquired about toys (boy toys and girl toys are not equal in my car when my kids get to actually have mcdonalds). When the second teenager came back with her toy answer, she said, "Oh and also, there's dairy in our french fries." She had to get a manager to get my money back, but I was very grateful that teenager number one had started asking around after taking my order until she found someone better informed. My stomach thanks her, too.
They gave me five of my six dollars back (I kept my drink) and then also gave me the burger. I just looked it up and found I can have that, but I'm a tad nauseous after the first few bites, so not sure what my body isn't liking.