Joseph Belleau, M.D.
Sneezing is not always the symptom of a cold. Sometimes, it is an allergic reaction to something in the air. Health experts estimate that 35 million Americans suffer from upper respiratory tract symptoms that are allergic reactions to airborne allergens.
Pollen allergy, commonly called hay fever, is one of the most common chronic diseases in the United States. Worldwide, airborne allergens cause the most problems for people with allergies. The respiratory symptoms of asthma, which affect approximately 11 million Americans, are often provoked by airborne allergens. Overall, allergic diseases are among the major causes of illness and disability in the United States, affecting as many as 40 to 50 million Americans.
What is an allergy?
An allergy is a specific reaction of the body's immune system to a normally harmless substance, one that does not bother most people. People who have allergies often are sensitive to more than one substance. Types of allergens that cause allergic reactions include:
Why are some people allergic?
Scientists think some people inherit a tendency to be allergic from one or both parents. They probably, however, do not inherit a tendency to be allergic to any specific allergen. Children are more likely to develop allergies if one or both parents have allergies. In addition, exposure to allergens at times when the body's defenses are lowered or weakened seems to contribute to developing allergies.
What is an allergic reaction?
Normally, the immune system functions as the body's defense against invading germs such as bacteria and viruses. In most allergic reactions, however, the immune system is responding to a false alarm. When an allergic person comes into contact with an allergen, the immune system treats the allergen as an invader and gets ready to attack.
The signs and symptoms of airborne allergies are familiar to many.
Some people with allergy develop asthma, which can be a very serious condition. The symptoms of asthma include coughing, wheezing and shortness of breath. The shortness of breath is due to a narrowing of the airways in the lungs and to excess mucus production and inflammation. Asthma can be disabling and sometimes fatal. If wheezing and shortness of breath accompany allergy symptoms, it is a signal that the airways also have become involved.
Is it an allergy or a cold?
There is no good way to tell the difference between allergy symptoms of runny nose, coughing, and sneezing and cold symptoms. Allergy symptoms, however, may last longer than cold symptoms. Anyone who has any respiratory illness that lasts longer than a week or two should consult a health care provider.
Each spring, summer and fall, pollen is released from trees, weeds, and grasses, which can enter human noses and throats, triggering a pollen allergy. Many people know this as hay fever. Many foods, medicines or animals that cause allergies can be avoided to a great extent, but short of staying indoors with the windows closed, when the pollen count is high, there is no easy way to avoid airborne pollen.
There are thousands of types of molds and yeasts. Although both can probably cause allergic reactions, only a small number of molds are widely recognized offenders. 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 allergy symptoms.
Dust Mite Allergy
Dust mite allergy is an allergy to a microscopic organism that lives in the dust found in all dwellings and workplaces. House dust, as well as some house furnishings, contains microscopic mites. House dust mite allergy usually produces symptoms similar to pollen allergy and also can produce symptoms of asthma.
House dust mites, which live in bedding, upholstered furniture and carpets, thrive in summer and die in winter. In a warm, humid house, however, they continue to thrive even in the coldest months. The particles seen floating in a shaft of sunlight
include dead dust mites and their waste products. These waste products, which are proteins, actually provoke the allergic reaction.
Household pets are the most common source of allergic reactions to animals.
Many people think that pet allergy is provoked by the fur of cats and dogs. Researchers have found, however, that the major allergens are proteins in the saliva. These proteins stick to the fur when the animal licks itself.
Urine is also a source of allergy-causing proteins, as is the skin. When the substance carrying the proteins dries, the proteins can then float into the air. Cats may be more likely than dogs to cause allergic reactions because they lick themselves more, may be held more, and spend more time in the house, close to humans.
Allergies to animals can take two years or more to develop and may not decrease until six months or more after ending contact with the animal. Carpet and furniture are a reservoir for pet allergens, and the allergens can remain in them for four to six weeks. In addition, these allergens can stay in household air for months after the animal has been removed.
Testing for allergies is the best way to find out if a person is allergic.
Allergists use skin tests to determine whether a person has antibodies in the skin that react to a specific allergen. The allergist will use weakened 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 a person's skin or is applied to a tiny scratch or puncture made on the arm or back. With a positive reaction, a small, raised, reddened area with a surrounding flush will appear at the test site.
Skin testing is the most sensitive and least costly way to identify allergies. People with widespread skin conditions like eczema, however, should not be tested using this method.
There are other diagnostic tests that use a blood sample to detect levels of antibody to a particular allergen.
If you cannot adequately avoid airborne allergens, your symptoms often can be controlled by medicines. You can buy medicines without a prescription that can relieve allergy symptoms. If, however, they don't give you relief or they cause unwanted side effects such as sleepiness, your health care provider can prescribe antihistamines and topical nasal steroids. You can use either medicine alone or together.
You should not use over-the-counter or prescription decongestant nose drops and sprays for more than a few days. When used for longer periods, these medicines can lead to even more congestion and swelling of the nasal passages.
Immunotherapy, or a series of allergy shots, is the only available treatment that has a chance of reducing your allergy symptoms over a longer period of time. You would receive injections of increasing concentrations of the allergen(s) to which you are sensitive. These injections reduce the level of antibodies in the blood and cause the body to make a protective antibody.
- National Institutes of Health