Pediatric allergy is a branch of pediatrics which deals with all the allergic reactions of children. Pediatric allergy/allergic reactions occur when the childrenâs immune system reacts to normal harmless substances present in the environment. Pediatric Allergy can be described as the disorder of immune system in children. Some of the Allergic reactions in children include, red eyes, itchiness, runny nose, eczema, hives and an asthma attack. A substance or an agent which is responsible for allergic reaction is called an âallergenâ.