<<Disclaimer: Verify this information before applying it to your situation.>> While a true "all-beef" patty is fine -- do be aware of hamburgs with fillers. We find that many times restaurants buy hamburgs with fillers -- Ask before ordering -- "I'm on a VERY struct diet - can't eat gluten". If you say "wheat", they will look at ingredients and miss modified food starch, oats, etc. Tell them you want a list of the ingredients from the box. If they can't give it to you, you are taking a chance. By the way, McDonald's and Burger King typically have ingredients lists -- their burgers are ok if right off the grill. Just tell them "a plain patty right off the grill, don't take it off the bun please, even a crumb will make me very sick!" It's ok to scare them a little if it will make them more concientious.