The term allergy is used to describe a response, within the body, to a substance, which is not necessarily harmful in itself, but results in an immune response and a reaction that causes symptoms and disease in a predisposed person, which in turn can cause inconvenience, or a great deal of misery.Allergy is extremely widespread and affects approximately one in four of the population in the UK at some time in their life. Each year the numbers are increasing by 5% with as many as half of all sufferers being children.