How can I go without eating for four hours without becoming hungry?

I am about to go to a friend’s party and there will be a lot of food there. I would eat the food there if I could but I have allergies and I can’t have anything offered there. I know I should have planned ahead but I didn’t and now don’t have anything I can bring. What are some ways I can focus on other things and not get so bummed out that I can’t eat anything when everyone else is eating?