An allergy is an overreaction of the immune system to substances known as allergens. In most people, allergens cause no reaction; for people affected by allergies, however, common reactions include upper respiratory tract symptoms like sneezing, wheezing, and coughing; itchy, watery eyes; and skin reactions. A more-severe respiratory symptom of an allergy is asthma. Allergens can be present in the environment (outdoor allergies), at home (indoor), and in foods and drugs; pets can also cause allergies. According to the National Institute of Allergy and Infectious Diseases, as many as 40 to 50 million Americans are affected by allergies.
An allergy, or allergic reaction, occurs when a person who has an allergy is exposed to an allergen. The immune system overreacts in response to the allergen, causing the symptoms of an allergy. Examples of common allergens include pollen, pet dander, dust, and mold.
Airborne allergens enter the body through the nose and lungs (in other words, are inhaled). Examples of airborne allergens include pollen from grass, trees, and weeds; household dust (including dust mite particles); mold spores; and cat and dog dander.
Allergens can also be absorbed through the skin. Plants such as poison ivy, poison oak, and sumac can affect people this way.
Additional ways people are exposed to allergens include through food (shellfish and nut allergies are common examples) and through injected medications (penicillin, for example, is a well-known cause of a drug allergy). Insect bites or stings can also cause allergic reactions.
It’s not well understood why some people are affected by allergies and others are not. It is thought that allergies can run in families and that exposure to allergens during illness, when the body’s defenses are lowered, may result in the development of allergies in some people.
Possible indoor allergens include pet dander, dust mites, mold, and cockroaches. Indoor allergens are airborne and then settle on furniture and floor surfaces, where they may remain for some time.
To control indoor allergies, you’ll need to clean your home thoroughly and regularly. This involves removing items like carpets, overstuffed furniture, stuffed toys, non-encased mattresses, and any pillows or bedding that are not washable in hot water. And, unfortunately, if pets are the source of you indoor allergies, you may want to consider finding them a new home. Suggested cleaning practices include keeping all surfaces (floors, countertops, and walls) clean and free of clutter, vacuuming at least once a week (using a HEPA—high efficiency particulate air—filter), and dusting with a damp cloth. Wearing a dust mask when you clean can control exposure to household allergens.
To control mold and dust mites, reduce the humidity in your home. Air conditioners can reduce humidity, as well as keep outdoor allergens like pollen from entering the house if you keep the windows closed.
If cockroaches are a problem, keep food and garbage covered and use poison baits, boric acid, and traps to kill and remove them. (Avoid chemical cockroach control agents, as these may irritate your sinuses and lungs.)
Pet fur is often blamed for causing pet allergies (often to cats and dogs), but the actual cause of these allergies is the pet’s dander (dead skin that is shed), which collects on the fur and other surfaces. As well, a pet’s saliva or urine can carry potential allergens. Once shed, these allergens don’t lose their strength for a long time and can adhere to walls, clothing, and other surfaces. So you can still react to these allergens, even after the pet has been removed.
Symptoms of pet allergies tend to affect the eyes (inflammation), nose (congestion), lungs (coughing, wheezing, shortness of breath), and skin (redness or rash).
The best treatment for pet allergies is to avoid contact with pets or, if you have a pet, to find it a new home. For many people, however, parting with their pet is not a desirable option. If this is the case, there are several things you can do to help manage your allergies:
You may have a good idea of substances you’re allergic to before you talk to you doctor or undergo medical testing. Are your eyes itchy and watery during the spring when certain plants are in bloom? Do you sneeze when you pet a dog or cat? Do you become congested every time you visit a certain home or building? These reactions may indicate allergies, and noting their pattern—including suspected triggers and frequency—can help you and your doctor diagnose your allergies.
Your doctor can take additional steps to test for and identify your allergies. Be prepared to share your personal and medical history, as this may offer clues. Your doctor may then examine your ears, eyes, nose, throat, chest, and skin to look for signs of allergic reaction. Several tests may also be conducted—a skin test, blood test, or patch test.
Approaches to treating allergies include avoiding your allergens, medication, and immunotherapy (allergy shots). You and your doctor will consider your medical history and the severity of your allergies to select the treatment that is best for you.