How Antihistamines and Decongestants Work

When a person comes into contact with an allergen it triggers that person’s immune system to take action. The immune system has cells called ‘mast cells’ and these release a substance known as histamine. Histamine attaches itself to receptors in the blood vessels which causes them to enlarge themselves. It also attaches itself to some other receptors, which then cause redness, itching, swelling and changes in regular secretions. Therefore by blocking these histamine receptors, the antihistamines taken are able to prevent these symptoms.

Decongestants work in a slightly different way. When an allergic reaction is taking place, tissues in a person’s nose will swell in reaction to the contact with that specific allergen. That swelling in turn produces mucus and fluids. The blood vessels that are in the eyes also swell up, which causes redness. The decongestants ease these symptoms by shrinking the swollen nasal tissue and enlarged blood vessels back to their normal size in order to relieve the symptoms of the allergic reaction like nasal swelling, mucus secretion, congestion and general redness. This is why antihistamines and decongestants are often prescribed in tandem, as they each treat different but equally important aspects of allergy symptoms, which helps you to feel worlds better.