You are gluten intolerant and follow a strict gluten-free diet. As a result of avoiding gluten for many years, your tolerance of gluten is very low (in other words, you get very sick if you ingest gluten).
When you dine out you have to be very cautious and always double check everything before ordering your meal.
You attend a restaurant who offer the option of a gluten free pizza. You go as far as to double check the sauce doesn't have gluten in it, just to be safe. You are assured it's fine. Your companion orders a regular pizza and you go with the gluten free pizza.
When the pizzas arrive they look the same. You are apprehensive, but your companion is of the opinion that the eatery would not make such a mistake because after all, you double checked.
A few hours later and you are violently ill.
How would you handle this? Just a complaint to the eatery, or would you take it further? Perhaps write a scathing online review?
This happened to a family member of mine and I'm curious to see how others would react.