Some of us will stay inside and hide from the people, parties and food. Others will venture our side of their comfort zone to try some food, knowing they may get sick. Why would they do that? Simply because they want to feel 'normal' and fit in.
To make the event a little better for you, it is best (I know - not as fun) to stay with foods that you know you can tolerate. As an extra step, I always take a small cooler of 'foods' that I can tolerate, drinks and emergency medications. This way I know I will be able to have something at the event. You can either slip out and eat it at your car, or take it with you. There is no shame in eating what your body will tolerate in front of others. This is how we survive (and with less side effects). Lastly, if they ask you to bring a dish, that is your chance to bring a dish that you can eat!
What ever you decide to do today, I hope you have a good day and enjoy it to the best of your ability!
