| INTRODUCTION — Asthma is a chronic lung condition that causes inflammation and constriction of the airways and difficulty breathing. Asthma attacks, or worsening of asthma symptoms, can occur after exposure to factors known as triggers.
Not all patients with asthma have the same triggers. Finding out which factors trigger an attack and taking steps to avoid the triggers are important parts of good asthma management.
IDENTIFYING AND MANAGING TRIGGERS — Careful attention to the pattern of asthma symptoms is an important part of identifying triggers. For example, if symptoms occur primarily at home, something in that environment may be involved. If symptoms flare in the spring or fall, an outdoor allergy is more likely to blame.
Additional information about possible asthma triggers can sometimes be gained by using blood tests or skin tests to see if a patient is sensitive (or allergic) to a particular substance.
Once asthma triggers have been identified, the patient has several options:
- Avoid the trigger entirely.
- Limit exposure to the trigger if it cannot be completely avoided.
- If a trigger is encountered in a predictable manner, consult with a healthcare provider about taking an extra dose of medicine before exposure to the trigger.
- Immunotherapy (allergy shots) can sometimes be helpful.
INDOOR TRIGGERS — Allergens are substances that can produce an allergic reaction and are major triggers in many people with asthma. Sensitivity to indoor allergens is especially common in asthmatics. The most common indoor allergens that affect asthmatics are dust mites, mold, animal danders, and cockroaches. The bedroom of the asthmatic person should be given special consideration because the greatest number of hours are typically spent there. However, to be effective, measures must be made to reduce allergens throughout the entire home.
Dust mites — Dust mites are microscopic organisms that are present in most households. They avoid light and absorb humidity from the atmosphere (ie, they do not drink). Mites may live in bedding, sofas, carpets, or any woven material if the humidity is high enough.
Measures that help limit exposure to dust mites are:
- Create a physical barrier to the source of the mites by covering pillows and mattresses with plastic or another impermeable fabric covers. A potential source of confusion when purchasing bedding covers is the availability of “hypoallergenic” unbleached or organic cotton bedding covers. These do not limit the passage of dust mites and are intended for people who have contact sensitivities to fabric dyes.
- Decrease the population of dust mites in the home by washing bedding in hot water and removing carpets and stuffed toys; these measures help to reduce nesting areas for mites.
- Control humidity. Mites thrive in humid environments. Opening windows in dry climates and using air conditioning in humid ones decreases humidity in the home and reduces the number of mites. Moving to or spending more time on upper floors of buildings may help, as upper floors tend to be less humid than lower floors or basements. Household humidity should be below 50 percent if possible. Inexpensive humidity monitors can be purchased at most hardware stores.
Mold — Mold spores can trigger asthma in allergic patients. Mold thrives in damp environments. Area such as air conditioning vents, water traps, refrigerator drip trays, shower stalls, leaky sinks, and damp basements are particularly vulnerable to mold growth if not cleaned regularly.
General measures to reduce mold exposure include the quick repair of any plumbing leaks, removal of bathroom carpeting which is exposed to steam and moisture, and scouring of sinks and tubs at least every four weeks with dilute bleach (1 ounce diluted in one quart of water); mold thrives on soap film that covers tiles and grout. In addition, indoor garbage pails should be regularly disinfected, and an electric dehumidifier should be used to remove moisture from the basement. Old books, newspapers, clothing, and bedding should not be stored in the home. Water damaged carpets should be thrown out because eliminating mold is difficult or impossible, even with thorough cleaning. For an important note about the use of bleach by people with asthma, see below (see “Irritants” below).
Animal danders — Asthma can be triggered by proteins from the “dander,” saliva, and urine of common house pets such as cats and dogs. Other warm-blooded animals, such as rodents, birds, and ferrets can also trigger asthma in an allergic individual. Pets without feathers or fur, such as reptiles, turtles, and fish, rarely cause allergy, although deposits of fish food that may build up under the covers of fish tanks are an excellent source of food for dust mite colonies.
Animal dander is made up of the dead skin cells or scales (like dandruff) that are constantly shed by animals. Any breed of dog and cat is capable of being allergenic, although the levels given off by individual animals may vary to some degree. In cats, the protein that causes most people’s allergies is found in the cat’s saliva, skin glands, and urinary/reproductive tract. Accordingly, short-haired cats are not necessarily less allergenic than long-haired animals, and furless cats give off similar amounts of allergen as furred cats.
If a person with asthma is found to be allergic to a pet, the pet should be removed from the home. Limiting an animal to a certain area in the house is not effective because some allergens are carried on clothing or spread in the air. Once a pet has left a home, careful cleaning of carpets, sofas, curtain, and bedding must follow. This is particularly true for cat allergens, as they are “sticky” and adhere to a variety of indoor surfaces. Even after a cat has been removed from a home and it has been thoroughly cleaned, it can take months for levels of cat allergen to drop . For this reason, it may take months for the allergic person’s symptoms to fully reflect the absence of the pet.
If it is not possible to remove the animal, measures can be taken to decrease exposure to the animal dander (show table 3), although none of these methods is as effective as removing the animal.
Cockroaches — Cockroach droppings contain allergens that have been shown to trigger asthma in sensitive individuals. Cockroaches thrive in warm environments with easily accessible food and water. Unfortunately, efforts to control cockroach populations in infested areas are often less than successful. Still, certain measures should be tried, including:
- Using multiple baited traps or poisons
- Removing garbage and food waste promptly from the home
- Washing dishes and cooking utensils immediately after use
- Removing cockroach debris quickly
- Eliminating any standing water from leaking faucets or drains
The role of air filters — Air filtering devices, including HEPA and other mechanical filters as well as electrostatic filters, are widely advertised and can be quite costly. These may be marketed as components of heating or cooling systems, as individual units for use in a room or area, or as units that are worn by individuals. None of these filtration devices have been scientifically proven to have a significant impact on asthma symptoms.
One possible explanation for this is that although these devices may clean the air, allergen levels cannot be effectively reduced unless measures are taken to eliminate their source. Thus, air filtration may be a useful adjunct to the measures described above, although we advise directing financial resources and efforts primarily towards eliminating sources of allergens.
CONTROLLING OTHER ASTHMA TRIGGERS — In addition to indoor allergens, other factors may be identified as asthma triggers.
Respiratory infections — Infections that cause airway inflammation can trigger asthma, including colds, influenza (flu), bronchitis, ear infections, sinus infections, and pneumonia. An asthma attack that occurs along with a respiratory infection may be more severe than one that occurs at other times. (See “Patient information: Influenza” and see “Patient information: Pneumonia in adults” and see “Patient information: The common cold in adults”).
To reduce the risk of a serious flare related to respiratory infection, a person with asthma should:
- Call a healthcare provider at the first sign of an infection.
- Get a flu shot once a year.
- Get a pneumonia vaccine (if needed based on other risk factors)
- Wash hands frequently, especially when in contact with an infected person, and avoid contact with infected people when possible.
- Use treatments prescribed for symptoms, such as nasal steroids and decongestants.
Allergies to food and medicine — Allergy to foods, especially foods containing sulfites (potatoes, shrimp, dried fruit, beer, wine) may trigger asthma in sensitive individuals. A food diary, listing all food and drink and chronicling asthma symptoms, may help isolate sensitivity to a particular food. If a sulfite allergy has been identified, the patient should be sure to read food labels to make sure sulfites are not present.
Sensitivity to medications can also trigger asthma. In particular, aspirin, some other anti-inflammatory drugs such as ibuprofen (Advil®, Motrin®) and naproxen (Aleve®, Anaprox®) and certain beta blocker heart medicines may cause an attack in certain individuals. Acetaminophen (Tylenol®) does not cause symptoms in most aspirin-sensitive patients.
Outdoor allergens — Asthma symptoms that worsen outdoors at certain times of year are likely to be triggered by an allergy to pollen or other plant material. Affected individuals should stay indoors as much as possible during the season when their asthma tends to flare and keep windows closed. Patients should also try to avoid cutting grass, digging around plants, or other outdoor activities that seem to worsen asthma symptoms.
Irritants — A variety of irritants can trigger asthma. Irritants can be found inside or outside, and include:
- Cigarette smoke and ashes — A person with asthma should never smoke, smoking should not be allowed in the person’s home, and second-hand smoke should be avoided whenever possible. (See “Patient information: Smoking cessation”).
- Aerosol sprays, perfumes — Non-aerosol products should be used, and exposure to offending perfumes avoided.
- Fireplace smoke and cooking odors — Wood-burning stoves, fireplaces, and pellet stoves should not be used, and cooking areas should be well ventilated.
- Air pollution, car exhaust, gas fumes — Patients should avoid unnecessary exposure to car exhaust, and outdoor exercise should be avoided when pollution levels are high.
Chemicals — Industrial or occupational exposure to chemicals is responsible for about 15 percent of cases of asthma. If symptoms tend to flare in a workplace where chemicals are in use, the patient and healthcare provider can discuss strategies to limit exposure.
If possible, patients whose asthma is triggered by strong odors should also avoid the use of chlorine and bleach-based cleaning products. If these cleaners are needed to control the growth of mold in the home, efforts should be made to ventilate the area thoroughly during and after use, and if possible, have a non-asthmatic person perform the cleaning.
Menstrual cycle — Worsening of asthma symptoms before or during menstruation has been reported in 20 to 40 percent of women with asthma. The reason for this phenomenon is unclear. Women with hormonally-triggered asthma tend to have more severe asthma than women whose asthma is unaffected by hormonal levels.
The optimal management of menstrual-associated asthma flares has not been determined, although women with a history of this problem are advised to increase their medication if necessary and avoid other potential asthma triggers.
Physical activity — Although exercise can trigger asthma in certain people, it should not be avoided. Exercise strengthens the cardiovascular system and may decrease sensitivity to asthma triggers. To minimize the effects of this trigger, asthmatics should:
- Take one or 2 puffs from an albuterol inhaler 5 minutes before beginning exercise
- Start any new exercise regime slowly, gradually building strength and endurance.
- Warm up gradually at the beginning of each exercise session.
- Take all medications on schedule.
- Avoid exercising outdoors in extremely cold weather and cover the mouth and nose with a scarf to help warm the inspired air when temperatures are low.
SUMMARY
- Asthma is a chronic lung condition that causes inflammation and constriction of the airways and difficulty breathing. Asthma attacks, or worsening of asthma symptoms, can occur after exposure to factors known as triggers (show table 1).
- Once asthma triggers have been identified, the patient has several options: avoid the trigger entirely, limit exposure to the trigger if it cannot be completely avoided, consult with a healthcare provider about taking an extra dose of medicine before exposure to the trigger, or consider immunotherapy (allergy shots), which can sometimes be helpful.
- Allergens are substances that can produce an allergic reaction in people who are sensitive (allergic) to them. Sensitivity to indoor allergens is especially common in asthmatics. The most common indoor allergens that affect asthmatics are dust mites, mold, animal danders, and cockroaches.
- In addition to indoor allergens, other factors may be identified as asthma triggers, including respiratory infections (colds, flu), allergies to food or medicines, outdoor allergens (pollen, grasses), irritants (cigarette smoke, aerosols, wood smoke, car exhaust), chemicals in the home or workplace, a woman’s menses, or physical activity.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.
This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information. Some of the most pertinent include:
Patient Level Information:
Overview of managing asthma
Professional Level Information:
Trigger control to enhance asthma management
Indoor allergen avoidance in the treatment of asthma and allergic rhinitis
A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.
- The National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
- American Academy of Allergy, Asthma, and Immunology
(www.aaaai.org)
- National Heart, Lung, and Blood Institute
(www.nhlbi.nih.gov/)
- National Lung Health Education Program
(www.nlhep.org)
- American Lung Association
(www.lungusa.org)
- American College of Allergy, Asthma, and Immunology
(allergy.mcg.edu/)
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REFERENCES
| 1. National Asthma Education and Prevention Program. Expert Panel Report: Guidelines for the Diagnosis and Management of Asthma Update on Selected Topics–2002. J Allergy Clin Immunol 2002; 110:S141. |
| 2. Platts-Mills, TA, Vervloet, D, Thomas, WR, et al. Indoor allergens and asthma: report of the Third International Workshop. J Allergy Clin Immunol 1997; 100:S2. |
| 3. Sporik, RB, Holgate, ST, Platts-Mills, TAE, Cogswell, J. Exposure to house dust mite allergen (Der p I) and the development of asthma in childhood: A prospective study. N Engl J Med 1990; 323:502. |
| 4. Wood, RA, Johnson, EF, Van Natta, ML, et al. A placebo-controlled trial of a HEPA air cleaner in the treatment of cat allergy. Am J Respir Crit Care Med 1998; 158:115. |
| 5. Cates, CJ, Jefferson, TO, Bara, AI, Rowe, BH. Vaccines for preventing influenza in people with asthma. Cochrane Database Syst Rev 2004; :CD000364. |
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