Antihistamine is the most common treatment for allergies. When the body is exposed to an allergen, it triggers the production of Immunoglobin E. This Immunoglobin is usually present in small amounts in the body. Its levels increase during an allergic reaction. This protein binds to mast cells and causes them to release histamine. Histamine binds to receptors on cells and blood vessels causing them to enlarge and release fluid. The result is swelling, inflammation, nasal congestion, runny nose, watery eyes and itchiness.

Antihistamines coat the receptors on cells and blood vessels thereby preventing histamine from binding to them. This in turn inhibits the effect of histamine and relieves allergic symptoms.

Antihistamines come in the form of nasal sprays, eye drops, ointments, pills and liquid. They begin to take effect with 15 to 30 minutes of use.

You can get antihistamines over the counter. Some antihistamines require a doctor’s prescription.

Most over the counter antihistamines cause drowsiness. If you need to work or drive, you can get a non-sedating antihistamine in a prescription form that doesn’t cause drowsiness.

You may need to antihistamines on a regular basis during the peak allergy season because they work very well before histamine is released. Once this mediator has been released, it acts really fast and this may reduce the effectiveness of an antihistamine.