Causes

Researchers think people may inherit the tendency to be allergic. Children are more likely to develop allergies if a parent has allergies, though they may not be allergic to the same substances. People who have allergies are often sensitive to more than one substance. Substances that cause the most allergic reactions include pollen, mold, dust mites, and pets.

Pollen

Pollen allergy, also known as hay fever, occurs seasonally—in the spring, summer, and fall—when trees, weeds, and grasses release tiny particles, called pollen, which are carried through the air. This is one of the most common chronic conditions in the United States, affecting an estimated 35 million people. In North America, most pollen comes from weeds, such as ragweed. Trees that produce allergenic pollen include oak, ash, elm, hickory, pecan, box elder, and mountain cedar. Few people are allergic to flowers. In fact, most people have little contact with the pollen of flowering plants, which is carried by insects, not the wind.

Mold

Molds are another cause of seasonal allergies. The mold season often peaks from June to late summer, though people who are allergic may have symptoms from spring to late fall. In the warmest parts of the United States, molds can cause year-round allergies. Molds are part of the fungus family, and their spores (reproductive particles) can produce allergic reactions when inhaled. In homes, mold is common in damp basements, bathrooms, refrigerator drip trays, houseplants, air conditioners, humidifiers, garbage pails, mattresses, and upholstered furniture. Molds can also be found in bakeries, breweries, barns, dairies, greenhouses, compost piles, and outdoor areas that are moist and shady.

Dust Mites

Dust mites are microscopic organisms in the dust found in all homes and workplaces. These mites can live in bedding, upholstered furniture, and carpets. They thrive in the summer and die in the winter, though in warm, humid homes, they can thrive year round. House dust, which is made up of a number of materials, contains dead dust mites and their waste products. It is these waste products that actually cause the allergic reaction.

Pets

Many people think that pet allergies are caused by the fur of cats and dogs. But researchers have found that the major allergens are proteins that come from the oil glands in the animals’ skin and are shed in dander. Saliva, which sticks in the fur when an animal licks itself, and urine are also sources of allergy-causing proteins. Some rodents, such as guinea pigs, gerbils, mice, and rats, can also cause allergic reactions in some people.

Symptoms

Signs and symptoms of allergies to airborne substances include:

• Sneezing, often with a runny or clogged nose
• Coughing and wheezing
• Itching eyes, nose, and throat
• Dark circles under the eyes (caused by increased blood flow near the sinuses)
• Red, swollen, or watering eyes

For people who have asthma, allergens can trigger asthma symptoms. Allergic reactions can also lead to sinusitis.

Your doctor can use skin tests to determine what allergens are causing your symptoms. In these tests, diluted extracts from different allergens are injected under the skin. If you have an allergic reaction, a small, raised, reddened area appears on the skin where you had the injection.

Treatment

Treatment for allergies often involves using self-care steps to avoid the allergen. Some people may also need medications or allergy shots.

Medications

There are several different types of medications that can help with allergic reactions:

• Antihistamines can be used to counter the effects of histamine, which is the chemical released by the body that causes allergy symptoms. Antihistamines can cause drowsiness; however, some of the newer medications available by prescription do not.
• Corticosteroid nasal sprays are very effective against allergy symptoms. It can take 3 to 10 days to get maximum relief, so you should start them as soon as you begin having symptoms.
• Decongestants can relieve symptoms caused by nasal allergies. They are available as oral medications and as nosedrops and sprays, but drops and sprays should only be used for a few days. When used for longer periods, they can make symptoms worse.
• Eyedrops containing antihistamines or decongestants can be prescribed to help relieve itchy eyes.

Allergy Shots

A series of allergy shots, also called immunotherapy, can be used to reduce allergy symptoms over a longer period. Allergy shots contain a small amount of the substance to which you’re allergic, which helps you become desensitized to the allergen. It can take 6 months or more to feel relief. Most people need allergy shots for at least a year and probably more for best results.

Self-Care

In addition to using medications, there are steps you can take to reduce your exposure to airborne allergens and the severity of your symptoms:

• Keep your windows and doors closed and use air conditioning at home and in your car during allergy season. Avoid using window and attic fans.
• Stay indoors in the morning and on dry, hot, windy days, when outdoor pollen levels are highest.
• Be aware that pollen can be brought indoors on people and pets.
• Dry your clothes in a dryer rather than hanging them outside, where they can collect pollen.
• If you are allergic to pollen but must work outdoors, wear a face mask designed to filter pollen.
• Avoid tobacco smoke, which can aggravate allergies.
• Use a good air filter at home.
• Run a dehumidifier at home to reduce humidity, which may allow mold to grow. Clean the dehumidifier often.
• Dustproof your bedroom: avoid wall-to-wall carpets, venetian blinds, down-filled blankets, and feather pillows. Bedding should be encased in a zippered, plastic, airtight, and dustproof cover. Pets should be kept out of the bedroom.
• Use a vacuum cleaner equipped with a high-efficiency particulate air (HEPA) filter.
• Washable items should be washed often using water hotter than 130°F. Lower temperatures do not kill dust mites.
• If you must live with a pet you are allergic to, someone else should bathe the pet weekly and brush it often.
• Avoid irritants that can make symptoms worse, such as insect sprays, tobacco smoke, air pollution, and fresh tar or paint.