What happens if you eat expired tomato sauce?

It depends on how expired the mayo is. If it is 2-5 days expired you should be fine. If it is 1-2 weeks expired you might get sick. I have the solution though. DON'T EAT EXPIRED MAYO! ALWAYS CHECK THE EXPIRATION! Another later ANS: GET SICK? What does that scare tactic mean? Just think for yourself. Keep the opened mayo in the cool fridge like the label always instructs. I have used mayo waaayyy past the printed expiry date and never had any bad physical reactions, and saved some hard earned $. "Sell by" dates DO NOT mean it is now spoiled rotten and totally uneatable. "Sell by" means only food store shelf life. If you own it and forgot to eat eat it: Judge by looking at it, smelling it, and tasting it... how hard is that?