Worst Food Allergy?

A little boy that lives next door to my parents had the longest list of food allergies you could think of. He couldn't have milk or milk products (that would kill me right there), wheat of any kind, eggs, and his sodium intake was severely limited and those were lots more things that I can't remember. That made me grateful I don't have food allergies and I don't have to read food labels for whatever I eat. What one thing would be the worst/most inconvenient food allergy to have? For me it would probably be milk... I love my icecream too much.