What Are Allergies?

Why Do I Have Allergies?
Testing For Allergies
How Do Allergies Develop?
Is it Allergies or a Cold?
How Are Allergies Treated?
Serious Situations
Allergy Myths

An allergy is your body's response by your immune system to a substance that is usually harmless. The immune system is a highly complex defense mechanism that helps us fight infection. It does this by identifying "foreign invaders" and then stimulating the body's white blood cells to fight them off. In some people, the immune system wrongly identifies a substance as harmful and so the person's own white blood cells overreact and do some damage to the body. Sounds confusing? It is a very complicated process. The allergic response becomes a disease in itself. No one really knows why some people are very allergic, although it seems to run in families. Common responses are: sneezing, nasal congestion, runny or itchy nose, itchy eyes, hives, headache, and fatigue.

The substances that provoke an allergic response are called allergens. Almost any substance can cause an allergic reaction. The most common ones are: pollen, dust, animal dander, animal hair, mold, medications, and food.

The medical term for nasal allergy symptoms is allergic rhinitis. ("Rhinitis" comes from the ancient Greek word "rhinos" for nose, and "itis" means inflammation.) Seasonal allergic rhinitis describes nasal allergies that change with the seasons due to pollen from plants. Hay fever, a popular term for seasonal allergies, is misleading because allergies seldom cause a fever and are not related to hay. Perennial rhinitis describes year-round nasal allergies, which are caused by substances like dust mites, mold spores, feathers, and pet dander.

Why Do I Have Allergies?

When your body mistakes something that is normally harmless for something dangerous, your body tries to get rid of it the same way it fights off an invading bacteria or virus. Your body's attempt to get rid of the allergen (foreign substance) causes an "allergic reaction." Symptoms like sneezing, watery eyes, and a runny, stuffy, or itchy nose, are what you experience. The first time your body encounters an allergen, your immune system may consider it harmful and form antibodies to it. With each repeated exposure, your immune system produces increased amounts of antibodies to the allergen until, eventually, you experience symptoms. With seasonal allergies, a couple of seasons may pass by before you experience any symptoms.

Diagnosing allergies is sometimes easy, and at other times very difficult. A patient's history and physical examination, may suggest certain allergies, which can usually be verified by a skin test. Other allergies -- notably food allergies -- are sometimes diagnosed by blood testing. Still others may require more extensive diagnostic efforts.

Skin tests are performed by injecting a small amount of an allergen just under the skin. This test is no more painful than a needle stick, and will usually give an indication within twenty minutes of application. Skin testing is the most accurate type of diagnosis for most allergies.

Blood testing requires sending a small sample of blood to an outside laboratory, and generally less accurate than skin testing. It may help to uncover food allergies, and is sometimes considered a useful diagnostic tool.

Food allergies can be difficult to pinpoint. Sometimes the only way to accurately diagnose food allergy is by the process of elimination -- to withhold a certain food substance from the diet for a period of time to observe whether symptoms disappear.

If an allergy is caused by a pet, down pillow, wool sweater, or certain food, removal of the allergen will eliminate the symptoms. We are not saying you have to get rid of your pet, but sometimes that will help your allergic response. If you have bad allergies, this is something to discuss with your family and health care provider if you test positive for allergies to cats and or dogs or feathers from your bird.

Complicated stuff, but you might be interested:

Your immune system fights off harmful foreign substances like bacteria and viruses by making antibodies to them. Each antibody recognizes and binds to one specific foreign substance -- like a key fitting into a lock. Millions of different antibodies circulate in your bloodstream and are present throughout your body to help fend off any unwanted substances.

The antibodies usually involved in allergic rhinitis are called "immunoglobulin E" (IgE). IgE binds to receptors located on certain cells in the nasal lining called basophils and "mast cells," which contain granules of a chemical called "histamine." When IgE binds to these cells, they "degranulate," releasing histamine. The released histamine latches onto nearby blood vessels, causing them to dilate (widen). This results in swelling, redness, and inflammation and leads to unpleasant symptoms such as an itchy, stuffy, or runny nose.

Each allergen produces a distinct set of IgE antibodies. You may have several different IgE antibodies in your body, indicating multiple allergies. The quantity of IgE antibodies present determines the strength of your allergic reaction. The more IgE antibodies you have to a specific substance, the more pronounced the reaction will be.

Is it Allergies or a Cold?

Although allergies and colds have similar symptoms, there are some signs that can help you tell the difference between them. It's probably an allergy if:

You have no fever.

Mucus secretions are clear and runny.

Sneezes occur in rapid, multiple sequence.

Itchiness in nose, ears, and throat (especially the palate or roof of the mouth) is present.

Symptoms last longer than the typical duration of a cold, which is usually 7 to 10 days.

If you aren't sure if you have a cold or allergies, your health care provider can help determine the cause of your symptoms and find appropriate treatment. See common cold for more...

Experts agree that the best way to treat allergies is to avoid exposure to the allergens in the first place. But sometimes that's impossible to do. Many different treatments are now available to relieve allergy symptoms, ranging from over-the-counter antihistamine medications to allergy shots. Because different treatments have different benefits and drawbacks, it is best to see your health care provider to determine which treatment is best for you.

Some common medications used to treat allergies include antihistamines and decongestants. Antihistamines are often used to relieve mild-to-moderate allergy symptoms like itching, sneezing, and runny nose. A decongestant may help relieve a stuffy nose. Sometimes, an antihistamine and a decongestant are used together to relieve multiple symptoms. Talk to your health care provider about trying different allergy treatments. He or she may refer you to an allergist. You may have to try a couple of different treatments before you find one that is right for you.

Other Treatments for Allergies

In addition to antihistamines and decongestants, Nasal Sprays and Immunotherapy are used to treat allergies. Ultimately, your allergist or health care provider will help determine which treatment is best for you.

Nasal Sprays:
Available over-the-counter and by prescription, nasal sprays can also be part of your defense against allergies. See Allergy Medication Table.

Corticosteroid nasal sprays, available by prescription only, are used daily to relieve congestion. They generally take at least a week to achieve maximum benefit.

Nasal sprays containing cromolyn sodium are also available to prevent sneezing and an itchy, runny nose caused by mild to moderate allergies.

Nonprescription nasal sprays containing a saltwater solution are sometimes used to relieve mild congestion, loosen mucus, and prevent crusting. They may be taken safely until symptoms improve.

Immunotherapy:

Immunotherapy -- also known as allergy shots -- can significantly reduce, but not eliminate, allergy symptoms. Injections of small amounts of allergens are increased gradually over time to desensitize the immune system. It takes about 6 months for allergy shots to start working, and the entire process can take up to 5 years.

Other Allergies

Inhaled allergens are considered the most common cause of allergies, but there are many other causes of allergies too -- including food, latex, drugs, and insect stings. Food allergies are common in children, although many people lose their sensitivity to foods over time. Some people have severe and possibly life-threatening reactions after eating or drinking "trigger" foods such as shellfish, eggs, milk, wheat, peanuts, or other nuts.