MODEL RELEASED. Food challenge. 10-year-old boy undergoing a double-blind oral food challenge to test for a food allergy. The boy will eat a variety of foods one by one, while being watched for symptoms of an allergic reaction by a doctor. The foods will include suspected allergens and placebos. Neither the patient nor doctor know which foods are which. Symptoms of an allergic reaction include local or systemic swelling and a rash. More serious reactions can cause a drop in blood pressure and breathing difficulties. This is known as anaphylactic shock and can be fatal in minutes. A food challenge is used after other tests, such as skin tests, to confirm an allergy.