During the challenge, you will be exposed to the allergen in small doses. For example, according to NPR, a fifth grade girl in Colorado had been allergic to eggs for most of her life. She began the food challenge by tasting a small bit of egg and waiting twenty minutes for a reaction. When she didn’t have one, they kept increasing her bite size and monitoring her reactions over the span of four to six hours. Eventually, she was able to eat an entire egg without a reaction, meaning she passed the test and it's safe to re-introduce eggs to her diet.