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The airways in a person with asthma are very sensitive and react to a variety of external factors, or "triggers." These triggers cause the airways to tighten and become inflamed and blocked with mucus, resulting in difficulty breathing. An acute asthma attack can begin immediately after exposure to a trigger or hours or days later.

There are many kinds of triggers, and responses to them vary considerably from person to person. A trigger may be harmless to some asthmatics but contribute to an inflammatory response in others—and an individual's reaction to any trigger may vary from one exposure to the next. Some people are affected by numerous triggers; others may not be able to identify any. Recognizing and avoiding triggers, when possible, is an important way to control asthma. Common asthma triggers include:

  • Infections, including colds, bronchitis, sinus infections, and the flu
  • Outdoor allergens, including tree, grass, and ragweed pollen, and mold spores
  • Indoor allergens: molds, animal dander, dust mites, cockroaches
  • Food allergies (not a common trigger, but can cause asthma symptoms, usually in children under age 5)
  • Exercise
  • Tobacco smoke
  • Wood smoke
  • Strong odors from perfumes, cleaning agents, etc.
  • Air pollution
  • Weather: cold air or changes in temperature and humidity
  • Strong emotions such as anxiety, or episodes of crying, yelling, or laughing hard
  • Certain medications
  • To control symptoms, it's important to first take note of what factors may have caused them and then avoid those triggers. (Exception: The only trigger you do not want to avoid is exercise. If your asthma is well controlled, you should be able to participate in any activity you want. (See our section on managing exercise.)

    This section includes information on how to reduce your exposure to common triggers in the environment, including:

    • Infection
    • Dust mites
    • Mold and mildew
    • Insects
    • Pollens
    • Pets
    • Irritants
    • Stress
    • Tobacco smoke
    • Food
    • Asthma triggers: infection

      When you have asthma, any infection—a cold, the flu—can affect the lungs, causing inflammation and constricting airways. It is important to take measures to stay healthy and be aware of any lung symptoms, even mild, so that you can avoid an asthma attack.

      • Sinus problems can trigger asthma episodes, so pay attention to symptoms and seek treatment promptly.
      • Talk to your doctor or healthcare provider about getting a flu shot every year, and get the pneumonia vaccine if you have not had one.
      • If friends have cold or flu symptoms, ask them not to visit until they are feeling well. If possible, try to stay away from large crowds in the fall and winter when the flu season is at its peak.
      • Wash your hands with soap and warm water, especially before preparing food, eating, and taking medications or breathing treatments and after coughing or sneezing, using the bathroom, touching soiled linens or clothing, and spending time with someone with a cold or the flu.
      • Keep breathing equipment used to treat asthma clean. Do not let others use your medical equipment.
      • Call your doctor if you experience symptoms of an infection, including shortness of breath, difficulty breathing, wheezing, coughing up increased amounts of mucus, yellow or green mucus, fever (temperature over 101°F) or chills, increased fatigue or weakness, sore or scratchy throat, sinus drainage, nasal congestion, headaches, and tenderness along upper cheekbones.

        Asthma triggers: dust mites

        Dust mites are microscopic creatures that live in carpets, mattresses, and upholstered furniture. They are present in almost all houses in the United States. To reduce exposure to dust mites, people with asthma should do the following:

        • Encase pillows, mattresses, and box springs with allergen-proof, zippered covers.
        • Wash all bedding in hot water about once a week.
        • Noncarpeted flooring is best. If you cannot get rid of carpeting, vacuum often with a multilayer, allergen-proof vacuum bag. Wear a mask when vacuuming. If your child has asthma, do not vacuum while he or she is in the room. Your healthcare provider can give you information about products that eliminate dust mites from carpeting.
        • Avoid heavy curtains or drapes; instead use washable window coverings. Wash window coverings in hot water every two to four weeks. Use plain window shades instead of miniblinds.
        • Dust all surfaces often, including lampshades and windowsills, with a damp cloth.
        • Keep clutter under control. Toys and books should be stored in enclosed bookshelves, drawers, or closets.
        • Replace traditional stuffed animals with washable stuffed animals.
        • Keep all clothing in drawers and closets. Keep drawers and closets closed.
        • Cover air ducts with filters or cheesecloth. Change these when soiled.
        • Use pillows and bedding that do not contain feathers.
        • Keep indoor humidity low (25 to 50 percent). Use a dehumidifier.
        • Regularly change filters on heaters and air conditioners.
        • Asthma triggers: mold and mildew

          In the outdoors, molds are a necessary part of the environment and help break down organic matter. Unfortunately, these tiny plants also grow on many common building materials—when they become damp—used in homes. Mold spores, the reproductive "seeds" of molds that are invisible to the naked eye, enter homes through open doorways and windows, heating and air conditioning systems, human clothing, and pet hair.

          Molds grow where leaks have occurred in roofs, pipes, and walls, where there has been flooding, and in damp basements or crawl spaces. They can develop within 24 to 48 hours of water exposure and will continue to grow until steps are taken to eliminate the source of moisture and remove the existing mold. To reduce exposure to mold, you can do the following:

          • Air out damp, humid areas, like the basement. Run a dehumidifier to keep humidity between 25 and 50 percent.
          • Use air conditioners when possible.
          • Clean bathrooms regularly using products that kill and prevent mold. Use exhaust fans to vent steam. Do not carpet the bathroom.
          • Keep indoor plants out of bedrooms.
          • When painting, add mold inhibitor to paint.
          • Avoid sources of outdoor molds, such as wet leaves or garden debris.
          • If you believe you have a serious mold problem or have existing health problems (especially respiratory problems), consider hiring a contractor who has experience with cleaning mold.
          • Because mold releases mold spores when disturbed, use extreme caution when cleaning and removing items that are moldy or consider hiring a professional.
          • If mold is growing in your home, you have a moisture problem that needs to be addressed. Steps to take include fixing leaky pipes, repairing damaged roofing material that has allowed moisture into your home, and making sure the ground around the house slopes away from the house to keep the basement and crawl space dry.
          • Do not use a fan if mold is already present. Fans will blow and spread mold spores throughout the home.
          • Insulate cold surfaces, such as cold water pipes, to reduce the potential for condensation.
          • Routinely check moisture-prone areas such as bathrooms and basements for signs of mold. Make sure these areas are ventilated (open doors and windows as needed), and clean them more frequently. Disinfect surfaces with a 10 percent bleach solution.
          • Make sure your home has adequate ventilation, including exhaust fans in the kitchen and bathroom.
          • Asthma triggers: insects

            Some people with asthma are allergic to cockroaches and other insects in the home. To control these allergens, you can do the following:

            • Use roach baits or traps.
            • Have your home or apartment sprayed with insecticide—but not when you're there. Be sure it's aired out for a couple of hours before you come home.
            • Asthma triggers: pollens

              Pollens, which spread in the breeze from trees, grasses, and weeds, are difficult to avoid. You can lessen exposure by following these guidelines:

              • Pollen counts are highest from the early morning until midday. Limit outdoor activities during this time.
              • Keep windows closed during pollen seasons.
              • Use air conditioning if possible.
              • To remove pollen from hair and clothing, shower after outdoor activities.
              • Asthma triggers: pets

                If pets are a trigger for asthma, here's some advice:

                • It is best not to own a pet if you or your child is highly allergic. Definitely avoid pets that have been shown to cause reactions.
                • If you decide to own a cat or dog, restrict its living area, and keep it out of your bedroom. If possible, keep the pet outside the house.
                • Wash the animal weekly.
                • Long visits to friends and family with pets should be avoided. If you do visit, asthma medicine should be taken before arrival, and exposure to the pets should be kept to a minimum.
                • Do without carpeting wherever possible. Animal dander will stay in carpeting even after the pet is gone from the home.
                • Asthma triggers: irritants

                  To avoid irritants, follow these guidelines:

                  • NO SMOKING! Smoking should not be permitted near anyone with asthma, especially in the home or car. Always request smoke-free hotel rooms and rental cars. Avoid places where smoking is permitted, and always sit in nonsmoking sections of public places. The lingering effects of cigarette smoke can irritate airways long after the smoking has stopped. (See our section on preventing tobacco smoke)
                  • Avoid using aerosol sprays, paint, and cleaning agents with heavy odors around a person with asthma. Make sure your home has proper ventilation. Wear a mask or handkerchief over your mouth when dusting, vacuuming, sweeping, or working in the yard.
                  • Do not use perfumes or other highly scented products that may irritate your lungs.
                  • Avoid wood smoke.
                  • If you live in an area where air pollution is a problem, limit outdoor activities when pollution counts are high.
                  • Avoid underground parking garages, which trap exhaust fumes.
                  • Avoid high-traffic or industrialized areas whenever possible.
                  • Avoid extreme weather conditions; during cold weather, cover your face with a scarf. During extreme humidity, try to stay in air-conditioned areas.
                  • Asthma triggers: stress

                    Stress and anxiety can make you feel short of breath and may worsen asthma symptoms. You cannot avoid stress; it's a given of daily life. However, developing effective ways to manage stress can help you prevent an attack.

                    • Learn to change thought patterns that produce stress. What you think, how you think, what you expect, and what you tell yourself often determine how you feel and how well you manage rising stress levels.
                    • Reduce the causes of stress. Identify the major stressors in your life, such as money problems, relationship problems, grief, or too many deadlines. If you can't manage these stressors alone, get professional help.
                    • Try to avoid situations that trigger stress for you. Practice effective time-management skills, such as setting priorities, pacing yourself, and taking time out for yourself. You can free up time and decrease stress by delegating responsibilities.
                    • Practice relaxation exercises, combining deep breathing, releasing of muscle tension, and clearing of negative thoughts. Many commercial audiotapes and books are available that teach these exercises.
                    • Exercise. Being active is an excellent way to burn off the accumulated effects of stress.
                    • Get enough sleep. If you are not sleeping well, you will have less energy and fewer resources for coping with stress. Developing good sleep habits is very important.
                    • Seek support from your family. Social support is the single most important buffer against stress. Family and friends can lift your spirits, help with household chores and with errands, learn what they can about your condition and prescribed treatment by attending doctors' appointments with you, provide encouragement, and help you follow your prescribed treatment plan.
                    • Asthma triggers: tobacco smoke

                      When a person inhales tobacco smoke, irritating substances settle in the moist lining of the airways and can set off asthma attacks. The smoke causes the lungs to make more mucus than usual and damages the tiny hairlike projections in the airways called "cilia" that normally sweep dust and mucus out of the airways. As a result, mucus and other irritating substances build up in the airways. In fact, people with asthma who smoke often have ongoing symptoms despite medical treatment.

                      Second-hand smoke is dangerous, too. The combination of smoke from a burning cigarette and a smoker's exhalations (also called passive smoke or environmental tobacco smoke) contains more harmful tar, carbon monoxide, nicotine, and other substances than what a smoker inhales directly.

                      There are a number of steps you can take to protect yourself or your child from tobacco smoke:

                      • If you smoke, quit. If your spouse or other family members smoke, help them understand the dangers of smoking and encourage them to quit. Ask your healthcare provider to help you find the stop-smoking method that works best for you.
                      • Do not allow smoking in your home or your car.
                      • Do not permit your child's caregiver to smoke.
                      • Avoid restaurants and public places that permit smoking.
                      • Asthma triggers: food

                        Although food allergies are not a common trigger of asthma, food allergies can lead to anaphylaxis, which includes wheezing and breathing difficulty. People with asthma may find that certain foods trigger their asthma symptoms along with other symptoms, such as hives, vomiting, diarrhea, abdominal cramping, and rashes around the mouth and other parts of the body. The asthmatic reaction to food allergies is most common in infants and children. If you think you or your child may have a food allergy that triggers wheezing, consult an allergist to determine exactly what you are allergic to and how best to avoid it. Here are some common food triggers and information on food in which they may be found:

                        • Shellfish: In some cases, a doctor can identify exactly which type of shellfish causes a reaction, but most food-allergy sufferers who react to shellfish must simply eliminate all types from their diet. Be careful with fried foods, since some restaurants use the same oil to fry shrimp, chicken, and french fries. Also, keep in mind that imitation shellfish may contain some actual shellfish for flavoring.
                        • Soybeans: If your doctor is unable to identify precisely which soy product is the trigger, it is best to avoid them all. But that's not always easy, since many products contain soy in some form. Examples of soy products and of foods that may contain soy include: soy flour, protein, fruits, nuts, milk, and sprouts; textured vegetable protein (TPV); hydrolyzed-plant, vegetable, or soy protein; natural and artificial flavorings; vegetable gum, starch, and broth; miso, soy sauce, and Worcestershire sauce; tofu, tamari, and tempeh; some cereals, infant formulas, and baked goods. Many people are allergic to more than one legume; other potential triggers in the legume family include navy beans, kidney beans, string beans, black beans, pinto beans, chickpeas, lentils, carob, licorice, and peanuts.
                        • Nuts: If you suffer from a nut allergy, strictly avoiding nuts and food containing nuts is the only way to prevent a reaction. In addition to nut-based butters and flours, foods that may contain nut ingredients include hydrolyzed-plant and vegetable proteins, nougat, marzipan, cereals, some ethnic dishes, cookies and other baked goods, candy, grain breads, ice cream and frozen desserts, energy bars, and salad dressing. Because prepared foods can be contaminated with peanuts if manufacturers prepare them in the same place as other products containing peanuts, it's important to be prepared for this possibility and the risk of a reaction.
                        • Last reviewed on 8/26/08

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