If you have these sudden attacks of itchiness, asthma, sneezing, coughing, rashes and red spots all over your body, chances are, you are allergic to something. Common allergies and their symptoms can manifest anytime and anywhere...A food allergy is an unusual reaction to certain type of food allergen.An allergen is the substance or thing that causes the allergic reactions.Exposure to the allergen sets off the alarm in the human immune system which consequently releases antibodies to fight off the invasion of the perceived foreign body that is the food allergen.It then causes the symptoms you would see when you are in a state of allergic reaction.