According to this USA Today article, "Wendy's researchers knew customers wanted warmer and crunchier buns, so they decided that buttering them and putting them through a toaster was the way to go."
Antico says, "people with food allergies should always inform restaurant employees about their food allergies and ask about ingredient lists, dedicated fryers and possible cross contact - even if they've comfortably eaten at that establishment in the past."
To stay on top of menu changes, consider the free Allergy Eats app for iPhone or Android. Adventures in Fast Food has a list of every fast food chain I can think of, with a link to each website and each menu.
So the lessons here are to be safe, stay informed and speak up about food allergies when eating out. Menus get updated, restaurant training and practices change, so never assume that something from your favorite restaurant is safe even if you've eaten it 1000 times.
By the way, I love Allergic Girl's latest post about dining out. Great lessons!