Wildfire in Tysons is good with allergies too. I believe the servers have to fill out a form about allergies when a customer mentions. With all of the restaurants mentioned on this thread, I would call in advance to make sure they can accommodate you. This advice is mentioned frequently by Tom Sietsema (wp food critic).

I've had excellent experiences with Founding Farmers as well as Ted's Bulletin & Matchbox for pizza only (part of same restaurant group) and GAR (Sweetwater, Coastal Flats, Artie's, Best Buns). Avoid Ping Pong Dim Sum, hey cannot guarantee safety and they are very up front about that. Clyde's and Old Ebbitt and the Hamilton were good about it too now that I think about it, just not crazy about their average food.

2Amys and Pete's Apizza were very understanding too as well as Daily Grill. I would skip Lebanese Taverna b/c of walnuts in so many things but Cava Mezze was good, kinda the same food if that's what you were looking for. If you reserve on OpenTable you can specify your needs in the comments section.