Allergy is the exaggerated reaction of the body of an individual to substances that are generally harmless to most people. This reaction is brought about by the body's immune system. The body immediately produces chemicals in response to these particles which result in the various symptoms of allergy.   

These foreign particles which trigger the reactions are known as 'allergens' and the tendency to develop these reactions is called as 'atopy'. 

  • The individual is usually genetically predisposed to react in such an inappropriate way to these foreign particles, and not everyone exposed to these will react the same way. 
  • Allergies can affect any part of the body, however, the most common organs involved are the skin, upper airway, lower airway, gastrointestinal tract and eyes.
  • In a predisposed person, when the allergen first enters the body, the body first produces a substance called 'IgE antibody'. This binds to immune cells called the 'Mast cells' and stimulates them to release inflammatory substances. Now the person is considered 'sensitized' to this allergen. When this person is exposed again to the same allergen, these Mast cells immediately recognises it and reacts by producing more inflammatory substances. This is what we call an 'allergic reaction'.

Depending on the organ it affects, people with allergy can present with red and watery eyes, recurrent colds and blocked nose, cough and wheezing, skin rashes or vomiting. Hence it is important to identify the allergic reaction and treat it with medicines which reduced this inflammatory reaction of the body.

It is also important to identify which allergens cause these problems with a allergy test so that avoiding them can prevent such responses again.