Airborne Allergies

An allergy is an exaggerated or inappropriate response of the immune system to a substance that is harmless to most people. Substances that can cause such reactions are called allergens. Common allergens include pollen, dust particles, certain foods, insect venom, mold, and medications. Doctors think that the reason



Concerns some people are allergic to a particular substance is because they have inherited a tendency to be allergic (although not necessarily to that particular substance). Being exposed to a potential allergen when the body's defenses are lowered or weakened—such as during a viral infection—seems to contribute to the development of an allergy. People with allergies are often sensitive to more than one allergen.

During an allergic reaction, the immune system is responding to a false alarm. When a person comes into contact with an allergen, the immune system launches an inappropriate immune response by releasing large amounts of an antibody (a disease-fighting protein) called immunoglobulin E. Each time the person encounters an allergen, these antibodies signal the body to produce powerful chemicals, such as histamine, that travel to where the allergen is located (such as the airways, the skin, or the surface of the eye) and cause inflammation. Symptoms of inflammation include redness, swelling, pain, and warmth. When pollen, dust, or other airborne allergens cause inflammation of the mucous membrane that lines the nose, the condition is known as allergic rhinitis. Common symptoms include runny nose, coughing, nasal congestion, and sneezing.

One of the most common allergies is pollen allergy. Each spring, summer, and fall, trees, weeds, and grasses release tiny particles called pollen, which ride on currents of air. The pollen enters the nose and throat, triggering allergic reactions in susceptible people. Among North American plants, weeds, especially ragweed, are the most prolific producers of pollen. In fact, the popular term "hay fever" typically refers to allergy to ragweed pollen. Other important pollen-producing weeds include sagebrush, redroot pigweed, tumbleweed, and English plantain. Trees that produce allergic pollen are oak, ash, elm, hickory, pecan, box elder, and mountain cedar. Although a wide variety of grasses grow in North America, only about seven types produce pollen that causes allergic responses.

Each plant has a pollinating period that is the same from year to year. The relative lengths of night and day seem to be the trigger for pollination, so the farther north you live, the later (and shorter) the pollinating period and the later (and shorter) the allergy season. A pollen count measures how much pollen is in the air at a given time. Pollen counts tend to be highest early in the morning on warm, dry, breezy days and lowest on chilly, wet days. If you have allergic rhinitis, try to stay indoors as much as possible on high-pollen-count days, especially in the morning. If you work outdoors, wear a face mask that filters out pollen. If possible, take your vacation at the height of pollen season and go to a location, such as the beach, where pollen counts are minimal.

House dust probably is the most common cause of airborne allergies, producing symptoms of allergic rhinitis. House dust is a mixture of potential allergens. It often contains fabric fibers, cotton lint, feathers and other stuffing materials, bacteria, mold, food particles, bits of plants and insects, and dust mites (micro-

scopic insects). Dust mites live in bedding, upholstered furniture, and carpets. 381

They thrive in summer, and they can live all year in warm, humid houses. The Immune mites produce waste-containing proteins, which are the actual causes of the system allergic reaction. Waste products of cockroaches also are are an important cause of allergy symptoms in infested households, especially in urban areas.

If you have a dust allergy, take the time to dustproof your home, especially your bedroom. Eliminate as many dust-gathering and dust-producing items— such as wall-to-wall carpeting, blinds, down-filled blankets, feather pillows, forced-air heating vents, pets, and closets full of clothing—as you can. Encase your mattress in a zippered, plastic, dustproof cover. Wash all of your bedding once a week in water hotter than 130 degrees Fahrenheit. Frequently wipe with a damp cloth all surfaces where dust accumulates.

Many people are allergic to animals, particularly household pets. Pet allergy is not triggered by the dander or hair of dogs or cats but rather by proteins in their saliva, which they transmit to their hair through licking. An animal allergy can take 2 or more years to develop and may not subside until 6 or more months after contact with the animal has ended. The best way to avoid an allergic reaction is to stay away from animals—even if it means finding a new home for a beloved pet. To decrease the level of cat allergens, try bathing the cat weekly, which neutralizes the protein on the fur. And keep the animal out of the bedroom.

Mold is a type of fungus that grows seasonally and causes allergic reactions in some people. Mold levels peak in late summer but, in warmer climates, molds thrive all year and can cause allergic symptoms year-round. Molds can be found wherever there is moisture. Outside, they grow on rotting logs and decomposing leaves. In the house, molds thrive in basements, bathrooms, damp closets, refrigerator drip trays, houseplants, air conditioners and humidifiers, garbage cans, mattresses, and old foam rubber pillows. When inhaled, tiny mold spores often evade the protective mechanisms of the nose and upper airways and reach the lungs. There they can cause bronchospasm (temporary narrowing of the airways in the lungs) or trigger an asthma attack (see page 245) in a person who has asthma.

To minimize your contact with allergy-triggering molds, have someone else mow your lawn and rake leaves, or wear a tight-fitting mask when you do these chores. Clean and disinfect your bathroom fixtures regularly, and be sure to air out closets, mattresses, pillows, and garbage cans. Regularly clean your air-conditioner filter and your humidifier filter and water reservoir according to the manufacturer's instructions. A dehumidifier can help dry out your basement, but you must clean the machine frequently to prevent mold buildup.

In addition to sneezing, coughing, runny nose, and nasal congestion, people with allergic rhinitis also may have itchy, watery eyes and conjunctivitis (an inflammation of the lining of the eyelids). Dark circles typically appear under the eyes, caused by increased blood flow near the sinuses. Some people



Concerns with allergies may develop asthma, a serious and potentially life-threatening respiratory disorder that causes tightness in the chest, wheezing, and sometimes severe shortness of breath.

Your health history (see page 82) is an important tool that can help your doctor diagnose a potential allergy. While taking your medical history, he or she can determine whether your symptoms recur at the same time each year, which suggests a seasonal allergen such as pollen. The doctor also will ask questions to determine what substances seem to trigger your allergies. To confirm this information, the doctor may perform skin testing, in which tiny amounts of suspected allergens are applied to, injected under, or scratched onto the skin. A small, reddened area will appear in the area where any substance to which you are allergic was applied. Blood tests also may be performed to detect blood levels of antibodies to a specific allergen.

Doctors generally recommend three approaches to the treatment of allergies: avoidance, medication, and allergy injections. For some people, complete avoidance of an allergen such as pollen or mold may require moving to a location where the allergen does not grow. Others may need to give up a favorite pet. If you have allergies, you may not be able to completely avoid the substances that provoke an allergic reaction. That is why doctors try to control allergic symptoms with medications, sometimes in combination. The most common medications prescribed for this purpose include antihistamines, which counter the effects of histamine, the inflammation-inducing chemical released by the body during an allergic reaction. Nasal corticosteroids, which are sprayed into the nose, combat inflammation, swelling, and mucous secretion. Another nasal spray, called cromolyn sodium, prevents allergic reactions from starting. Effective antihistamines and decongestants also are available over the counter. Ask your doctor for recommendations.

Taking a series of allergy injections (immunotherapy) is the only method of reducing your allergy symptoms over the long term. This treatment usually is given over the course of 2 or 3 years. The doctor injects you with gradually increasing doses of the allergen. In response, your body decreases production of antibodies to that substance and begins producing protective antibodies instead. About 85 percent of people with allergic rhinitis experience a substantial reduction in their symptoms within 2 years of beginning their allergy injections.

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