If I ate at a fast food restaurant that cooked their chicken in the same grease as their shellfish and had an allergic reaction, can I sue the restaurant?
Question Details: I had to go to the hospital.
You would not have a cause of action unless you had specifically told the restaurant that you were allergic to shellfish, asked whether they cooked their chicken in any way together with the shellfish, and they'd told they did not, and, based on what they said, you ordered the shellfish and were sickened. Otherwise, they did nothing wrong: it is not uncommon for one food to be cooked using the same grease, gravy, sauce, etc. as another, and unless the restaurant is aware that a patron has an allergy, they do nothing unreasonable--and so nothing negligent--by doing what is common and cooking foods together.
Furthermore, even IF they were liable, you cold only sue to recover (1) actual out-of-pocket (not paid by insurance) medical costs, (2) lost wages, if any, and (3) "pain and suffering" if you incurred significant, long-lasting life impairment; that is because you can only recover for actual, not theoretical, injury. If you did not incur significant costs or suffer a significant impairment, then if the restaurant were liable, it would not be worth suing, because you'd spend more on the lawsuit than you could recover.