Irritants As Asthma Symptom Triggers

Substances may cause an attack—even when you're not allergic to them

In This Article

Asthma irritants are airborne substances that act as an asthma trigger when inhaled. They differ from allergens in that they do not generate an immune response. Instead, they irritate already inflamed airways and trigger asthma symptoms, including wheezing, shortness of breathchest tightness, and chronic cough. By identifying asthma irritants in your home, at work, and elsewhere in your environment, you can find ways to avoid them and reduce your risk of an attack.

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Easy Tips for Reducing Asthma Triggers

How Irritants Cause Asthma

Asthma is an obstructive airway disease in which bronchi and bronchioles of the lungs are extra-sensitive (hyperresponsive). When provoked by an asthma trigger, the airways become inflamed, narrow, and produce excess mucus, inducing the symptoms recognized as asthma.

Asthma irritants cause attacks in a slightly different way than allergens:

  • With allergens, the body responds by releasing antibodies, called immunoglobulin E (IgE), into the bloodstream. This provokes the release of defensive white blood cells—most predominately eosinophils—that incite inflammation in the airways that trigger an asthma attack.
  • With irritants, there is no IgE response. Instead, the body responds as it would to any foreign substance: by activating the epithelial cells that line tissues to release white blood cells—most predominately neutrophils—that incite the inflammatory response. When this occurs in already hypersensitive airways, asthma can result.

Because airborne irritants are delivered to the very tissues where asthma occurs, they provoke symptoms directly. By contrast, allergens can provoke asthma either directly (e.g., by inhaling pollen, dander, or molds) or indirectly (e.g., by eating food you are allergic to).

Other common triggers for asthma include viral infections, extreme climate, exercise, non-allergic drug reactions, non-allergic food intolerance, and stress, each of which provokes asthma in a slightly different way.

Common Asthma Irritants

The upper respiratory tract—composed of the nostrils, sinuses, mouth, throat, and larynx—is vulnerable to airborne irritants. It acts as the primary filter to these airborne infiltrates, trapping as many of them in mucus secretions lining the airways as possible.

Even people without asthma can react to these irritants. Non-allergic rhinitis is one such example in which inflammation of the mucus membranes triggers nasal stuffiness, sneezing, watery eyes, and runny nose.

Finer airborne particles, including those in dust and fumes, can bypass these upper respiratory "filters" and make their way into the lungs where they trigger an inflammatory response.

Airborne allergens like pollen and mold, for example, range in size from 1 micron (µm) to 1,000 µm. By contrast, airborne irritants like smoke and atmospheric dust can be as small as 0.01 µm to 0.001 µm in size. This can make airborne irritants all the more difficult to avoid if you have asthma.

Some of the most common asthma irritants are those you encounter every day at home, work, or the area in which you live.

Tobacco Smoke

Tobacco smoke, either firsthand or secondhand, is a powerful trigger for asthma symptoms. It contains over 7,000 chemicals that not only induce inflammation in the airways but provoke a generalized inflammation that affects almost every part of the body, including the heart, brain, skin, and blood vessels.

The consequences of tobacco smoke in people with asthma are well documented. According to the Centers for Disease Control and Prevention (CDC), no less than 21% of people with asthma are smokers. Those who smoke are far more likely to experience severe attacks and require hospitalization than those who don't. Smokers with asthma also tend to respond less well to inhaled corticosteroids used to control asthma symptoms.

Over time, exposure to tobacco smoke can cause the thickening and hardening of the airway walls (called remodeling) that increases hyperresponsiveness as well as the risk of acute attacks.

Secondhand smoke applies here too. Not only does it incite attacks in people with asthma, but it can also increase the risk of asthma in children. According to a 2012 review in the journal Pediatrics, young children with one or two smoking parents have anywhere from a 21% to 85% increased risk of developing asthma than those with no smoking parents.

Air Pollution

Air pollution can have just as dramatic impact on asthma symptoms as tobacco smoke but be inherently more insidious because people live in it. This is especially true in urban centers with a proliferation of hazardous airborne pollutants (HAPs).

HAPs are comprised not only of smoke but airborne particles as small as 0.001 µm is size. (By way of reference, the eye of the needle is 1,230 µm in size). Among the 33 HAPs classified as toxic in the Clean Air Act of 1990 are:

  • Arsenic
  • Benzene
  • Carbon tetrachloride
  • Chloroform
  • Coke oven emissions (resulting from industrial ovens used to heat coal for the manufacturing of steel and iron)
  • Dioxin
  • Formaldehyde
  • Lead
  • Mercury
  • Nickel
  • Quinolone

Of these, coke oven emissions emit substances like sulfur dioxide and ozone that are known to trigger asthma in children and adults. These same pollutants are emitted in car exhaust fumes, one of the major contributors to air pollution.

Living in areas with poor air quality places your lungs under persistent inflammatory stress. If you have asthma, this will almost invariably increase airway hypersensitivity and may even reduce your response to inhaled asthma medications.

Pollution can also increase your risk of getting asthma. A 2012 study published in Environmental Health Perspectives linked air quality to asthma in a telling way.

According to the researchers, living near a major roadway in Los Angeles County in California increases the risk of asthma due to the concentrated exposure to exhaust fumes. Based on the analysis, no less than 8% of asthma diagnoses in that county can be at least partly linked to air pollution.

Occupational Exposure

Aerosolized fumes and particles in factories, manufacturing plants, repair shops, and service stations can introduce other toxic chemicals into the lungs, triggering breathing difficulties. Referred to as occupational asthma or work-related asthma, the condition may affect as many as 21.5% of working people with asthma.

Such airborne irritants can also be found in non-industrial settings such as healthcare facilities, retail stores, restaurants, hair salons, or anywhere where chemicals or combustion processes are involved.

Among the irritants commonly associated with occupational asthma are:

  • Latex
  • Flour dust from cereal grains
  • Isocyanates
  • Persulphates
  • Aldehydes (like formaldehyde)
  • Animal products
  • Wood dust
  • Metal dust

Some of these substances (like latex, flour, and animal products) can also cause an allergic reaction that spurs an asthma attack. Others (like wood, metal, and aldehydes) simply act as airway irritants.

In some instances, the reaction to an occupational particle can be very specific and alter the course of one's disease.

For example, dust created from the weaving and cutting of textiles acts as a trigger in people with asthma. Over time, prolonged exposure can cause irreversible changes in the lungs, leading to a condition called byssinosis (also known as brown lung disease), which closely resembles chronic obstructive pulmonary disease (COPD).

Fragrance and Strong Odors

It is not uncommon for certain people to have a fragrance allergy, which generally occurs when a perfume or a fragranced substance comes in contact with skin. Other people may experience a reaction to the smell of the fragrance itself in which the aerosolized molecules act as irritants and trigger everything from rhinitis to a severe asthma attack.

Referred to as fragrance sensitivity, the reaction is related to abnormal activation of the autonomic nervous system—what regulates involuntary functions of the body (such as respiration).

The exact mechanism for odor-induced asthma is poorly understood, but it is believed that certain strong scents can trigger a chain reaction in which nerve receptors in the nose can suddenly overreact and release neurotransmitters that stimulate respiration, airway constriction, and mucosal secretions.

A 2014 study in the Journal of Psychosomatic Research found that stronger, undiluted scents, like perfumes and colognes, were more likely to trigger asthma than those that were diluted and perceived to be more neutral or "pleasant."

The fact that "pleasant" smells are less likely to cause asthma suggests that there may be a psychological component to odor-induced asthma. It is theorized that an abrupt exposure to a strong scent can trigger a stress response in which inflammatory compounds, called cytokines, are spontaneously released into the bloodstream, provoking an asthma attack.

The theory is supported by research in which exposure to a pungent cologne caused anywhere from an 18% to 58% drop in the forced expiratory volume (FEV1) in a group of adults with asthma. However, the longer they were exposed to the scent, the more normalized the FEV1 became.

Physiology and psychology appear to play dual roles in a fragrance's effects on asthma symptoms

Diagnosis

Experience will usually tell you which environmental triggers are provoking your attacks. The increased need for a rescue inhaler at work or during a smog alert, for example, can be a pretty reliable indication of the source of the problem. At other times, the cause may be harder to pin down.

Doctors will often recommend that you keep an asthma diary (similar to a food diary) in which you track your symptoms, things you were doing prior to the symptoms, and your peak flow meter results. By keeping an accurate record of these details, you can usually spot patterns that can help pinpoint the cause.

Because many asthma irritants do not provoke an allergic response, seeing an allergist and getting allergy tests may not be useful. Instead, you may need to see a pulmonologist for a non-invasive test known as a bronchoprovocation challenge.

Bronchoprovocation Testing

A bronchoprovocation challenge is an in-office procedure that measures your lung function after exposure to common asthma triggers. It is extremely useful in confirming asthma when routine pulmonary function tests (PFTs) are inconclusive.

As valuable as the test can be, it has limitations. First, many labs only perform non-specific challenges that can confirm you have asthma but offer little else. Those that perform specific challenges will only do so with non-toxic substances (like wood, dust, or coffee) or non-toxic amounts of a substance (like nickel, chromium, or PVC). Not every substance can be evaluated.

Secondly, specific bronchoprovocation tests have a high rate of false-positive and false-negative results, and there are few (if any) confirmatory tests that can support the diagnosis.

Even if a specific bronchoprovocation challenge test is strongly positive, the result will usually not change the course of your treatment. All it can really tell you is what substances you need to avoid. Nevertheless, bronchoprovocation challenges may be appropriate if attacks are recurrent and severe, and allergen testing offers no clues as to the causes for the attacks.

Treatment

There are few treatments for non-allergic asthma irritants other than the avoidance of the irritants themselves. This is sometimes easier said than done, especially if the exposure is work-related or you are a smoker.

Not every employer, for example, can move an employee to a "safe" space, and not every work environment allows for the use of the face masks to prevent exposure. Similar, quitting cigarettes is worthwhile but challenging, and often requires as many as 30 attempts before the habit is kicked.

Medications

Beyond the avoidance of specific irritants, the treatment of irritant-induced asthma is no different than that of regular asthma. This includes the appropriate use of short-acting beta-agonists (also known as rescue inhalers) to treat acute asthma symptoms.

If there is persistent asthma, daily controller medications, such as inhaled corticosteroids and long-acting beta-agonists, may help reduce airway hyperresponsiveness and control inflammation. Other medications may be added to the treatment plan based on the severity of your symptoms.

If you smoke, ask your doctor about smoking aids to improve your chances of quitting. Many are classified as Essential Health Benefits (EHB) under the Affordable Care Act and, as such, are fully covered by health insurance.

Prevention

If you have irritant-induced asthma, take your asthma medication as prescribed. Only around 35% of people on daily asthma medications take them consistently.

By taking your drugs as prescribed, you can reduce airway hyperresponsiveness and, with it, your sensitivity to asthma irritants.

In addition, do what you can to reduce your risk of exposure:

  • Avoid secondhand smoke. Start by letting your family and friends know about your condition, and discourage anyone from smoking near you or in your house. Find smoke-free restaurants, hotels, and rental cars.
  • Keep track of air quality. Many local TV stations and apps offer air quality reports. You could also consider purchasing an indoor air quality meter if you are especially sensitive.
  • Keep windows and doors shut. If the air quality is poor, stay indoors and use an air conditioner to cool the room rather than opening windows. The same applies when you are driving in traffic.
  • Use an air purifier. The best air purifiers use a multi-filter system (usually a HEPA filter combined with a charcoal-activated filter) and are able to remove particles as small as 0.3 µm. A humidifier can also help but can promote the growth of airborne molds if the unit and space are not immaculately clean.
  • Speak to your employer. If your exposure is work-related and your asthma is severe, let your employer know. Severe asthma can sometimes qualify as a work-related disability and may motivate your employer to relocate you to a safer department or provide you with protective gear to prevent exposure.
  • Wear a face mask. Choose the mask appropriate for your condition. If you are working in an industrial plant, a maximum filtration N95 particulate respirator may be appropriate. In other cases, a mask rated ASTM 1 (low), ASTM 2 (medium), or ASTM 3 (high) may be suitable.
  • Avoid fragrances. If you are especially sensitive to odors, only buy lotions, soaps, detergents, and cosmetics labeled fragrance-free or unscented. Ask car washes not to add scents to the interior of your car. Find hotels that offer hypoallergenic rooms that are less likely to use deodorizers or fragrances.
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