• Grasses and trees are important sources of allergenic pollens with more than 1,000 species of grass growing in North America. These include timothy grass, Kentucky bluegrass, Johnson grass, Bermuda grass, redtop grass, orchard grass, and sweet vernal grass. Trees that produce allergenic pollen include birch, oak, ash, elm, hickory, pecan, box elder, and mountain cedar.

• Weeds among North American plants, weeds are the most prolific producers of allergenic pollen. Ragweed is the major culprit, but others of importance are sagebrush, redroot pigweed, lamb's quarters, Russian thistle (tumbleweed), and English plantain.

• Dust mites.

• Molds and fungi: There are thousands of types of molds and yeast. However, only a small number of molds are widely recognized offenders. The seeds or reproductive particles of fungi are called spores. Each spore that germinates can give rise to new mold growth, which in turn can produce millions of spores. In a small number of people, symptoms of mold allergy may be brought on or worsened by eating certain foods, such as cheeses, processed with fungi. Occasionally, mushrooms, dried fruits, and foods containing yeast, soy sauce, or vinegar will produce allergic symptoms.

• Animals

• Cockroaches

• Rodent urine

• House dust

• Carbonless copy paper this causes an allergic contact dermatitis

• Adhesive backing on carpets

In some instances, high dust mite, cat, and dog allergen levels have been detected in schools and day care centers. Carpets in schools and homes are an important reservoir or "sink" for these allergens.²

Symptoms of Allergies

The signs and symptoms of allergies are well known and include:

• Sneezing

• Runny or clogged nose

• Sinus congestion

• Coughing

• Postnasal drip

• Itching eyes, nose, and throat

• Allergic shiners (dark circles under the eyes caused by increased blood flow near the sinuses)

• Watering eyes

• Eye inflammation

• Skin rash (allergic contact dermatitis) can be caused by sensitizers in the office including carbonless copy paper (formaldehyde, phthalic anhydride), carpeting components (latex backing, mold contamination, glues), laser printers and photoduplication equipment (acrylates, styrene, and other off-gassing thermal degradation products)

People with allergy symptoms, such as the runny nose of allergic rhinitis, may at first suspect they have a cold but the "cold" lingers. It is important to see a doctor about any recurrent or long-lasting respiratory illness.

Doctors often use skin tests to determine what substances to which someone is allergic. The doctor will use diluted extracts from allergens such as dust mites, pollens, or molds commonly found in the local area. The extract of each kind of allergen is injected under the patient's skin (intradermal) or is applied to a tiny scratch or puncture made on the patient's arm or back. If a person is allergic to a particular substance, a small, raised, reddened area (called a wheal) with a surrounding flush (called a flare) will appear at the test site. Current studies indicate that intradermal testing is nonspecific and is not useful for allergy resolution.

Although skin testing is the most common way to diagnose allergy problems, some people (such as those with skin conditions like eczema) need their allergies diagnosed another way. Another diagnostic test that may be used to diagnose allergies is an in vitro blood test called the RAST (radioallergosorbent) test. The RAST test is used when eczema is present, if a patient has taken medications that interfere with skin testing, or for household pets (like dogs) who may have allergies. In general, in vitro testing is preferred over skin tests, since it can be easily standardized.

Since allergy tests are often specific to plants that grow in a particular geographical area, one may need to go through allergy testing again if they make a move to a different part of the country where there are different types of plants.

How Allergies Are Treated 

There is no cure for allergies, though they can often be controlled. Many people, particularly children, experience a spontaneous resolution of allergic disease. A combination of three approaches is usually used. These are:

• Avoidance of the allergen or irritants

• Medication to relieve symptoms

• Allergy shots or allergy vaccines

Minimizing Exposure to Allergies 

• Complete avoidance of whatever triggers the allergic reaction is the best treatment. For example, if somebody is allergic to cats, they should not own or care for cats.
  
  Complete avoidance of allergenic pollen or mold may even mean moving to a place where the offending substance does not grow and where it is not present in the air. But even this extreme solution may offer only temporary relief since a person who is sensitive to one allergen may begin developing allergies to new allergens after repeated exposure. Physician advice should be sought before making decisions about relocation as a means to avoid allergen exposure.

• Avoid places where the allergen is present. For example if somebody is allergic to pollen, they should stay indoors in the morning when pollen levels are highest. They may also want to vacation in areas where pollen levels are low, like the seashore

• Mold allergens can be difficult to avoid, but some steps can be taken to reduce exposure to them. First, the allergy sufferer should avoid places where molds tend to be concentrated. The lawn should be mowed and leaves should be raked up, but someone other than the allergic person should do these chores.

• Try to control moisture around the house since high humidity levels encourage the growth of dust mites. In addition, moisture leads to fungus growth, another allergen. Around the home, a dehumidifier will help dry out the basement, but the water extracted from the air must be removed frequently to prevent mold growth in the machine.

• Use central air-conditioning to help control humidity levels

• Monitor humidity to see if relative humidity is a problem and if control efforts are working.

• Put impermeable covers on bedding (mattresses and pillows) of people with mite allergies and remove fleecy textiles.

• Keep the house clean. House dust mites, pollens, animal dander, cockroaches, and other allergy-causing agents can be reduced, although not eliminated, through regular cleaning.

• Use high-efficiency air filters installed in air-handling systems to help reduce the levels of some particulate agents in indoor air. Be sure they are the right size and avoid systems that add pollutants such as ozone and chemicals to the air.

• Before buying a room-size filtering device, the patient should rent one and use it in a closed room (the bedroom, for instance) for a month or two to see whether allergy symptoms diminish. The airflow should be sufficient to exchange the air in the room five or six times per hour; therefore, the size and efficiency of the filtering device should be determined in part by the size of the room. Check for independent validation of the air cleaner performance.
  
  Persons with allergies should be wary of exaggerated claims for appliances that cannot really clean the air. Very small air cleaners cannot remove dust and pollen, and no air purifier can prevent viral or bacterial diseases such as influenza, pneumonia, or tuberculosis. Buyers of electrostatic precipitators should compare the machine's ozone output with Federal standards. Ozone can irritate the nose and airways of persons with allergies, especially those with asthma, and can increase the allergy symptoms.

• Install and use a central vacuum system that exhausts air outside. If you do not have this, use a vacuum cleaner equipped with a HEPA filter to help reduce the spread of indoor allergens.

• Avoiding Irritants: People with allergies often are less able to tolerate exposure to irritants. Air fresheners, tobacco smoke, and hairsprays are examples of common indoor irritants that some people with allergies must avoid.

Medications to Reduce Allergy Symptoms 

There are three types of medicines that are mainly used to help control allergy problems:

• Antihistamines: As the name indicates, an antihistamine counters the effects of histamine, which is released by the body and contributes to allergy symptoms. For many years, antihistamines have proven useful in relieving sneezing and itching in the nose, throat, and eyes, and in reducing nasal swelling and drainage.

• Decongestants: Some nasal allergies cause symptoms such as congestion, swelling, excess secretions, and discomfort in the nose and sinus areas. Sinuses are hollow air spaces located within the bones of the skull surrounding the nose. Decongestants can help relieve these problems. Often they are taken along with antihistamines. Over-the-counter and prescription decongestant nose drops and sprays, however, should not be used for more than a few days. When used for longer periods, these drugs can lead to even more congestion, nosebleeds and swelling of the nasal passages.

• Topical nasal steroids: This medication should not be confused with anabolic steroids, which are sometimes used by athletes to enlarge muscle mass and can have serious side effects. Topical nasal steroids are anti-inflammatory drugs that reduce allergy specific inflammation. They help reduce mucus secretion in the nose and sinuses and reduce nasal swelling.

Allergy Shots

A series of allergy shots, or allergy vaccines, is the only available treatment that has a chance of reducing the allergy symptoms over a longer period. Patients receive subcutaneous (under the skin) injections of increasing concentrations of the allergen(s) to which they are sensitive. Many patients with allergies who take allergy shots will have fewer symptoms and may not need to take as much medication, often within 12 months of starting immunotherapy. These shots are useful only for a select group of allergy patients.

For more information about allergies or asthma, consider contacting the following organizations:

• Allergy and Asthma Network/Mothers of Asthmatics, Inc. (AAN/MA)
  A national, not-for-profit organization, AAN/MA provides asthma and allergy outreach to improve public and patient awareness and management of asthma. They serve as a valuable communication link among families, medical professionals, caregivers, the pharmaceutical and medical supply industries, and the government. For more information, visit their website at: www.aanma.org.

• Asthma and Allergy Foundation of America (AAFA)
  This not-for-profit patient advocacy organization is dedicated to finding a cure for and controlling asthma and allergic diseases. Education and support services are available to asthma and allergy patients and their families through AAFA's local education support groups and chapters nationwide. To find out more about AAFA, access the web at: www.aafa.org.

• Publication
  Horner WE, Lehrer SB, Salvaggio, JE. Aerobiology. In: Lockey RF, Burkhartz SC. Allergens and Allergy Immunotherapy, 2nd ed. New York, NY: Marcel Dekker, 1999:53-72. (212) 696-9000

1. Singh J. Impact of indoor air pollution on health, comfort and productivity of the occupants. Aerobiologia. 1996;12:121.

2. Fernández-Caldas E, Trudeau WL. Environmental control of indoor biologic agents. J Allergy Clin Immunol. 1994;2(2):404-412.