Rhinitis is an inflammation of the mucous membranes that line the nose. It produces symptoms like a stuffy nose, nasal congestion, runny nose, post nasal drainage, plugged ears, sneezing, itchy nose, itchy eyes, and itchy roof of the mouth and throat. With rhinitis, the nasal drainage is typically clear and not discolored. It can either be caused by allergies (i.e., allergic rhinitis) or by a cold, injury, or pollutants (i.e., nonallergic rhinitis).

Allergic rhinitis

If you are allergic to airborne things like grass pollen, weed pollen, tree pollen, dust, dust mites, pet dander, molds, etc., your body is overreacting and treating the substances you're coming in contact with, as if they were harmful. A substance in the blood called immunoglobulin (IgE) recognizes allergens and attaches itself to them. In fact, a different type of IgE is produced for each substance your body is allergic to.

The more IgE you have for the allergen, the worse your reaction to it. The IgE attaches to a cell in the nose called the mast cell and forms an allergy "bomb" that is then triggered whenever you inhale that specific allergen. The bomb releases histamine, which is what causes the watery eyes, runny nose, congestion, and all of those other miserable symptoms you have with allergies. This is the body's attempt at flushing the allergen out. The pollens themselves are not harmful in any way, but your bodies response to the pollen causes many unwanted symptoms.

Non-allergic Rhinitis

If your symptoms are not caused by allergy then you may have non-allergic rhinitis. This form of rhinitis is due to a reaction of the nose to a variety of irritants. The most common cause of non-allergic rhinitis is due to an abnormal response of the nose to various chemicals or irritants. These irritants can be things such as tobacco smoke, aerosol sprays like hair spray, perfumes, powders, paint fumes, insecticides, detergents or pollutants.

One type of non-allergic rhinitis is called vasomotor rhinitis and involves a reaction to temperature changes and barometric pressure changes. Another type of non-allergic rhinitis is called rhinitis medicamentosa and involves a reaction to certain medications such as nasal decongestant sprays like Afrin (generic: oxymetazoline) or Neosynephrine, certain heart medications, and many birth control pills containing estrogen. Other types of non-allergic rhinitis are due to nasal virus infections (the common cold, eg viral rhinitis). Non-allergic rhinitis symptoms are nearly identical to allergic rhinitis but are not caused by IgE in the blood stream. Instead, it is just a hypersensitivity of the lining of your nose to that particular irritant.