I have a friend who often get the shits after eating store bought pesto. I heard because of the ingredients (garlic, cheese, olive oil, and basil), pesto is quite perishable. On the other hand good pestos are loaded with olive oil, some people have trouble digesting oily foods. Can there be a way to tell?
With food poisoning, the clue is how many people get sick from eating the same food. If everybody at the picnic who ate Aunt Emma’s potato salad is now standing in line to the porta-potty, it’s a safe bet that the potato salad is a lab culture dish of some nasty bug.
If only one person is getting sick, then there might be one bite in the dish that was contaminated, OR your friend is sensitive to something in the food.
So then it would be a guessing game, what is the EXACT culprit?
With store bought food, there’s always the possibility of more ingredients that you don’t know about. If there is a label, read the fine print. There could be gluten, xanthan gum, spider legs…any number of things you wouldn’t necessarily associate with pesto.
Then Friend needs to figure out WHICH ingredient is the Bad Guy.
Food sensitivities/intolerances involve a LOT of trial and error.
~VOW