The nomenclature of allergy, hypersensitivity and intolerance is very often confused and is still controversial. Different terms are used in the United States and Europe. The European/WHO terminology is taken as standard. The most common classification of allergy is IgE mediated and non–IgE mediated. The IgE mediated is also termed as type 1 hypersensitivity and others are divided into type 2, type 3 and type 4. Mucosal epithelial cells which line the upper respiratory passage are affected by the acute allergic reactions. The interactions that take place between the allergens and the surface are complex and involves the autonomic nervous system and the mediators produced by the underlying tissues in response to allergens. Mucous glands which have goblet cells in the epithelium are induced to secrete mucus and the mucus genes are induced in the ciliated epithelium. This causes mucous metaplasia and hyperplasia. Thus, repeated and prolonged exposure leads to structural changes and enhanced mucus production. The tissues will be washed with cytokines and other inflammatory mediators which causes classical pictures of asthma.

A sincere effort has been made to find out the common allergens that cause the respiratory complications in the practice of ENT. This study is intended to help the fellow ENT practitioners to identify the commonly associated allergens and thus take immediate actions in diagnosing and treating the patient that present in complications in OPD.