Learn about Allergy

An allergy is an overreaction of the immune system to a normally harmless substance called an allergen. Common allergens include pollen, animal dander, down feathers, mites, chemicals and a variety of foods.

On first exposure the inhaled allergen enters the mucus membrane lining the nasal passages where it is taken up by the antigen presenting cell which presents it to the T-cells. These T-cells activate the B-cells to release substances called IgE antibodies against the allergen. These IgE antibodies sit on the surface of the mast cells. The mast cells have granules containing chemical mediators like histamine and prostaglandins, etc. On exposure, the allergen binds to the IgE antibodies present on the mast cells cross-linking them. This results in the release of histamine, prostaglandins and other mediators into the surrounding tissue. These mediators cause dilation of the surrounding blood vessels and increase their permeability. This results in the nasal stuffiness, sneezing and mucus discharge of allergic rhinitis. Anti-histamine work by blocking the action of histamines at its receptors and thus decreasing the body’s reaction to the allergen.


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