UK Allergy Profile

Allergies (a.k.a ‘hypersensitivities’) are overreactions of the immune system to substances that do not cause reactions in most people. Hypersensitivities are grouped into four types, I, II, III and IV. The two types of hypersensitivities are commonly associated with ’allergies’ are type I or ‘immediate’ hypersensitivities, and type IV or ‘delayed’ hypersentivities.
In type I hypersensitivity, a particular foreign substance (known as an ‘allergen’) reacts with a specific type of antibody called immunoglobulin E (IgE) – this reaction causes symptoms to appear within minutes.
In type IV hypersensitivity, the allergen reacts with a specialised type of cell called a T-lymphocyte. In this case symptoms take hours to days to appear.