What Are Allergies?

An allergy is a sensitivity to an ordinarily harmless substance such as dust or pollen. When you become allergic your body tries to rid itself of the foreign substance, known as an allergen. This process results in the symptoms people associate with allergies: sneezing, a runny, stuffy or itchy nose and watery eyes.

Some of the typical allergens include pet dander, pollen, dust, and mold. Allergic rhinitis is the medical term for nasal allergy symptoms (Rhinitis comes from the Greek word "rhinos" for nose, and "itis" meaning inflammation.)

Many people experience this unpleasant circumstance only at certain times during the year or during certain seasons. Seasonal allergic rhinitis denotes nasal allergies that change with the seasons due to pollen from plants, for example.

In 1828 a British physician, Dr. John Bostock, coined the term "Hay fever," a term for seasonal allergies, when he noticed that his symptoms worsened during the British haying season. This term, while popular, is somewhat misleading, because allergies seldom cause a fever and they are rarely related to hay.

Another all to common form of nasal allergy occurs year-round and is termed Perennial rhinitis which is caused by substances which have no seasonal variation like dust mites, mold spores, feathers, or pet dander.

How Are Allergies Treated?

Most experts agree that the best way to treat allergies is to avoid exposure to the allergens in the first place. Many times thats impossible to do. A variety of different treatments are now available to relieve allergy symptoms. These range from over-the-counter antihistamine medications, to prescription medicines, to allergy shots.

These remedies work to varying degrees, but because different treatments have different benefits and drawbacks, it is best to see your doctor to determine which treatment will give you the best overall result.

Antihistamines and Decongestants

The most common medications used to treat allergies are antihistamines and decongestants. Antihistamines are often used to relieve allergy symptoms like itching, sneezing, and runny nose. A decongestant may help relieve a stuffy nose and open up congested nasal passageways. The combination of an antihistamine and a decongestant are used together to relieve multiple symptoms.

What are antihistamines?

Antihistamines, are available in both prescription and over-the-counter forms. They help reduce the sneezing, itching, and runny nose resulting from an allergic reaction. They work by blocking the action of histamine. Histamine is a potent chemical that is released from certain cells when you are exposed to an allergen.

Antihistamines are most effective if they are taken over the period of allergen exposure. Thus they are not curative but are more preventative in nature, since if one stops the antihistamine while still exposed to the allergen, symptoms will often return.

One major disadvantage of many antihistamines, especially those available over-the-counter, is that they can cross the blood-brain barrier. This means they can travel easily from the bloodstream into the central nervous system, where they may cause sluggishness or drowsiness.

This sedating effect can be magnified if you combine the medication with alcohol or with certain other sedating medications. In order to overcome this drawback nonsedating antihistamines, available by prescription only, have been developed. These do not easily cross the blood-brain barrier, and therefore usually do not cause drowsiness when taken at the recommended dose.

Over-the-counter medication for cold and sinus that are labeled "nondrowsy" or "nonsedating" usually don't contain an antihistamine, only a decongestant. Unlike over-the-counter antihistamines, which must be taken more than once a day for maximum benefit, these prescription antihistamines are long-acting and thus are often once a day medications.

How do antihistamines work?

When you are exposed to an allergen, mast cells, located in the membrane lining the nose and sinuses, release a chemical called histamine. Histamine attaches to receptors on nearby blood vessels, causing them to dilate and become engorged with blood. Histamine also binds to other receptors located in the nasal tissues, leading to redness, swelling, itching, and an increase in nasal secretions.

Antihistamines "block" the histamine receptors, preventing these vascular and membrane changes that lead to the symptoms mentioned above. Antihistamines also block histamine from stimulating nerve endings, which can cause itching and other symptoms.

By blocking histamine, the cascade of events leading to the offending symptoms can be stopped before the process begins. So by following the first rule for allergy sufferers, namely avoidance, and by the proper use of antihistamines and decongestants some of the symptoms due to allergies can be overcome.