Patient education: Trigger avoidance in asthma (Beyond the Basics)

ASTHMA TRIGGER OVERVIEW — Asthma is a chronic lung condition with inflammation, 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.

A number of other topics about asthma are available separately:

●For adults (see "Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)") and (see "Patient education: How to use a peak flow meter (Beyond the Basics)" and "Patient education: Inhaler techniques in adults (Beyond the Basics)" and "Patient education: Exercise-induced asthma (Beyond the Basics)")

●For children (see "Patient education: Asthma symptoms and diagnosis in children (Beyond the Basics)" and "Patient education: Asthma inhaler techniques in children (Beyond the Basics)" and "Patient education: Asthma treatment in children (Beyond the Basics)")

IDENTIFYING AND MANAGING ASTHMA TRIGGERS — One of the best ways to identify asthma triggers is to pay careful attention to the pattern of asthma symptoms. 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 to pollen that pollinates during that season, such as tree (spring) or ragweed (fall), is more likely to blame.

Using blood tests or skin tests can provide additional information about possible asthma triggers by determining if a person is sensitized (or allergic) to a particular substance.

Once asthma triggers have been identified, there are several options:

●Avoid the trigger entirely.

●Limit exposure to the trigger if it cannot be completely avoided.

●If exposure to the trigger can be predicted, consult with a health care provider about taking an extra dose of medicine before exposure to the trigger.

●Immunotherapy (allergy shots). (See "Patient education: Allergic rhinitis (Beyond the Basics)", section on 'Allergy shots'.)

ALLERGIC ASTHMA TRIGGERS — Allergens are substances that can cause an allergic reaction and are major triggers in many people with asthma.

Indoor allergens — Sensitivity to indoor allergens is especially common in people with asthma, especially:

●Dust mites

●Mold

●Animal danders (skin, fur, saliva)

●Cockroaches

The bedroom should be given special consideration because the greatest number of hours are typically spent there. However, to be effective, multifaceted and thorough measures may be needed to reduce all relevant allergens throughout the 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). The highest concentrations of mites are in mattresses, but they may be found in other bedding, upholstered furniture, carpets, curtains, house dust, or any woven material if the humidity is high enough.

Measures that help limit exposure to dust mites are detailed in the table (table 1) and include the following:

●Create a physical barrier to the source of the mites by covering pillows and mattresses with plastic or another impermeable fabric cover designed for this purpose. Note that dust mite covers should not be confused with "hypoallergenic" bedding covers that are made of unbleached or organic cotton and are intended for people who have contact sensitivities to fabric dyes. Cotton covers are not useful for containing dust mites.

●Decrease the population of dust mites in the home by washing bedding and pillows in hot water and detergent or drying them in an electric dryer on the hot setting once per week.

●Remove carpets from the bedroom. Minimize the number of stuffed toys that collect dust in the child's bedroom and wash them weekly.

●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. Avoid using a humidifier.

●Use a mop or vacuum instead of a broom to clean the floor and surfaces may reduce exposure to aerosolized dust.

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. The household humidity should be between 30 and 50 percent, if possible. Inexpensive humidity monitors can be purchased at most hardware stores and online.

Mold — Mold spores can be found indoors in damp environments and trigger symptoms of asthma and allergic rhinitis in mold-allergic patients. Areas such as air conditioning vents, water traps, refrigerator drip trays, shower stalls, leaky sinks, and damp basements are particularly vulnerable to mold growth. Molds that originate outdoors can be found indoors as they can track inside through open windows and doors, on clothing and shoes, and on pets.

To reduce the growth of mold, it is necessary to remove existing mold and reduce humidity to prevent future growth of mold. Humidity can be reduced by removing sources of standing water and persistent dampness. Specific measures include eliminating rainwater intrusion, removing house plants, fixing leaky plumbing, correcting sinks and showers that do not drain completely, and removing bathroom or basement carpeting that is exposed to steam or moisture. Damp areas should be dehumidified to levels below 50 percent.

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 are potential reservoirs for mold and may need to be discarded. Water-damaged carpets should be thrown out because it is difficult or impossible to eliminate mold in this situation, even with thorough cleaning.

Mold thrives on soap film that covers tiles, sinks, and grout. Sinks, tubs, and other surfaces with visible mold growth should be cleaned at least every four weeks. Various cleaning agents can be used, such as white vinegar, borax, detergent, or dilute bleach (eg, 1 ounce [30 mL] bleach diluted in 1 quart [1 liter] of water). Other surfaces with visible mold growth should also be cleaned. The use of bleach by people with asthma is discussed below. (See 'Chemicals' below.)

Animal danders — Animal dander is made up of the dead skin cells or scales (like dandruff) that are constantly shed by animals. Asthma can be triggered by proteins from the "dander," saliva, and urine of common house pets, such as cats and dogs. 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 have allergens that are similar to furred cats.

Other warm-blooded animals such as rodents and ferrets also can 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 build up under the covers of fish tanks are an excellent source of food for dust mite colonies.

If a person with asthma is found to be allergic to a pet, the most effective option is to remove the pet 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, curtains, and bedding must follow. This is particularly true for cat allergens because 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 the level of cat allergens 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 (table 2), although none of these methods is as effective as removing the animal.

Cockroaches — Cockroaches can shed or excrete particles that 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 are recommended, including:

●Using multiple baited traps or poisons

●Sealing cracks and holes

●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 high-efficiency particulate air (HEPA) filters, other mechanical filters, and electrostatic filters, are widely advertised to reduce indoor allergens. They 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. These devices can be expensive, and not all studies show that air purification improves allergy symptoms or asthma, although some have. Studies also have shown that air filters can reduce the amount of particulate matter (from air pollution) in a home, which can also help reduce asthma symptoms. (See 'Irritants' below.)

Certain types of air filters (eg, ionizers) produce ozone, which is a respiratory irritant for some people. These devices have not been proven safe or effective and are not recommended (United States Environmental Protection Agency (EPA): Indoor air quality).

There are several factors that interfere with how well air filters work, and they may partly explain why studies have shown mixed results:

●Most air filters probably can remove pollens and pet danders from the air because these allergens are light and do remain airborne. However, if there is a pet, carpeting, upholstered furniture, access to outside air, or some other reservoir of allergen in the vicinity, the allergen is continuously released from these items as people move around the house. There is far more allergen in these reservoirs than the air filter can remove. Therefore, allergens continuously enter the air, even as it is being filtered, and the benefit of an air filter is minimal.

●In contrast, in a room where there are no carpets, drapes, upholstered furniture, access to outside air, and pets are not allowed, running an air filter probably can improve air quality.

In addition, a vacuum cleaner with a HEPA filtration system and a double-thickness bag can help to reduce allergen levels. This is recommended to avoid rebreathing the debris that is captured by vacuuming. The intervention of adding steam cleaning to frequent vacuuming with an HEPA filter-equipped vacuum has shown even more benefit for reducing dust mite allergens.

Outdoor allergens — Asthma symptoms that worsen outdoors at certain times of the year are likely to be triggered by an allergy to pollen or mold (often present in decaying vegetation). Affected individuals should stay indoors as much as possible during the season when their asthma tends to flare, use air conditioning when possible, and keep windows closed. Exercising outdoors or participating in activities that require exertion should be avoided when levels of air pollution or pollen levels are high. After spending time outdoors when pollen or mold counts are high, patients can bathe and shampoo to remove residual allergens.

Patients should also try to avoid cutting grass, digging around plants, or participating in other outdoor activities that seem to worsen asthma symptoms.

CONTROLLING OTHER ASTHMA TRIGGERS — In addition to indoor allergens, other factors, including those unrelated to allergies, 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 education: Influenza symptoms and treatment (Beyond the Basics)" and "Patient education: Pneumonia in adults (Beyond the Basics)" and "Patient education: The common cold in adults (Beyond the Basics)".)

To reduce the risk of a serious flare related to respiratory infection, a person with asthma should:

●Call a health care provider at the first sign of an infection.

●Get a flu shot once per 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.

Medicines — Sensitivity to medications can also trigger asthma. In particular, aspirin, some other antiinflammatory drugs, such as ibuprofen (Advil, Motrin [brand names]) and naproxen (Aleve, Anaprox [brand names]), and certain beta blocker medicines for the heart, eyes, or anxiety may cause an attack in certain individuals. Acetaminophen (Tylenol [brand name]) does not cause symptoms in most aspirin-sensitive patients. Additives are often added to medicines as the inactive ingredients, and a few cases have associated these with asthmatic episodes.

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 education: Quitting smoking (Beyond the Basics)".)

●Aerosol sprays and perfumes – Nonaerosol products should be used, and exposure to offending perfumes should be avoided.

●Gas stoves, fireplace smoke, and cooking odors – Wood-burning stoves, fireplaces, and pellet stoves and unvented gas stoves or heaters can worsen asthma symptoms. Cooking areas should be well ventilated.

●Air pollution, car exhaust, and gas fumes – Patients should avoid unnecessary exposure to car exhaust, and outdoor exercise should be avoided when pollution levels are high. United States air quality ratings can be obtained at airnow.gov.

●Formaldehyde and volatile organic compounds – Odors from new linoleum flooring, carpeting, particleboard, wall coverings, furniture, and recent painting may worsen asthma symptoms in some people.

Chemicals — Industrial or occupational exposure to chemicals is responsible for approximately 15 percent of cases of asthma. If symptoms tend to flare in a workplace where chemicals are in use, the patient and health care provider can discuss strategies to limit exposure. Other chemicals, such as environmental phenols, can be found in many consumer products, paper receipts from thermal printers, and in food and beverage container linings and have been associated with wheeze.

If possible, people whose asthma is triggered by strong odors should avoid the use of chlorine and bleach-based cleaning products. If these cleaners are needed to control the growth of mold in the home, ventilate the area thoroughly during and after use and, if possible, have a person without asthma perform the cleaning. Other troubling odors include perfumes, air fresheners, scented room sprays and candles, and cooking oils.

Menstrual cycle — Between 20 and 40 percent of females with asthma report that their asthma symptoms worsen just before or during their menstrual period (called perimenstrual asthma). Females with hormonally triggered asthma tend to have more severe asthma than females whose asthma is unaffected by hormonal changes. Perimenstrual asthma is thought to be triggered by changes in hormone levels, but exactly how it happens is unclear.

The best way to treat menstrual-associated asthma flares is not known. Some experts recommend the following:

●Use a rescue inhaler when necessary, and avoid other potential asthma triggers.

●Use of a leukotriene modifier (montelukast [generic name]/Singulair [brand name], zafirlukast [generic name]/Accolate [brand name], or zileuton [generic name]/Zyflo [brand name]) may help to prevent asthma flares related to hormonal changes.

●Females with asthma who are sensitive to antiinflammatory medications (eg, ibuprofen [generic name]/Advil and Motrin [brand names], naproxen [generic name]/Aleve [brand name], aspirin [generic name]) should not take these medications for menstrual cramps.

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, people with asthma should:

●Take one or two puffs from an albuterol inhaler five 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.

A detailed review of managing exercise-induced asthma is available separately. (See "Patient education: Exercise-induced asthma (Beyond the Basics)".)

Climate — Some triggers can be affected by climate changes and extreme weather events. For instance, in areas with ozone problems, hot, sunny days can mean increased response to ozone. Caution is advised under these circumstances. Thunderstorms can cause pollen grains to burst and release allergens. During pollen seasons, people with pollen allergies may notice asthma symptoms in the hours after a thunderstorm.

Sulfites — Sulfites are added to foods to prevent spoiling and discoloration. Foods containing sulfites (potatoes, shrimp, dried fruit, beer, wine, vinegar) may occasionally trigger asthma in sensitive individuals. If sulfite sensitivity has been identified, the patient should be sure to read food labels to make sure that sulfites are not present. Other food additives have not been well studied in this context.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Avoiding asthma triggers (The Basics)
Patient education: Asthma in adults (The Basics)
Patient education: Asthma in children (The Basics)
Patient education: Exercise-induced asthma (The Basics)
Patient education: Allergic bronchopulmonary aspergillosis (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)
Patient education: How to use a peak flow meter (Beyond the Basics)
Patient education: Inhaler techniques in adults (Beyond the Basics)
Patient education: Exercise-induced asthma (Beyond the Basics)
Patient education: Asthma symptoms and diagnosis in children (Beyond the Basics)
Patient education: Asthma inhaler techniques in children (Beyond the Basics)
Patient education: Asthma treatment in children (Beyond the Basics)
Patient education: Allergic rhinitis (Beyond the Basics)
Patient education: Influenza symptoms and treatment (Beyond the Basics)
Patient education: Pneumonia in adults (Beyond the Basics)
Patient education: The common cold in adults (Beyond the Basics)
Patient education: Quitting smoking (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Allergen avoidance in the treatment of asthma and allergic rhinitis
Trigger control to enhance asthma management

The following organizations also provide reliable health information.

●US National Library of Medicine (medlineplus.gov/healthtopics.html)

●American Academy of Allergy, Asthma & Immunology (www.aaaai.org/)

●American College of Allergy, Asthma & Immunology (acaai.org/)

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ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledges William Bailey, MD, who contributed to earlier versions of this topic review.