Best way to assess if I’m intolerant to certain foods?

Food allergies run in the family but I’ve never conducted any tests to determine whether I’m intolerant to anything. I have brain fog and want to start looking into my diet as certain foods make me sick. I can’t eat any type of cakes or drink fizzy drinks.

Some family members are gluten free, dairy free etc.

Is there certain tests that I can get or is it trial and error by trying different diets?

Thanks 🙂

Thanks to the Courtesy of :

https://www.reddit.com/r/glutenfree/comments/dmdnr9/best_way_to_assess_if_im_intolerant_to_certain/