Asthma Explained: Causes, Symptoms, And Treatments

We've all had moments — maybe after a hard workout or while battling a cold — when it feels hard to take a nice, deep breath. But for individuals with asthma, not being able to breathe properly is a chronic, and sometimes very serious, concern. 

WebMD describes asthma as "a long-term disease of the lungs. It causes your airways to get inflamed and narrow, and it makes it hard to breathe." For some, asthma is only a minor nuisance that occasionally flares up because of exposure to certain triggers. For others, it's a daily battle that negatively impacts their ability to perform everyday activities or get a good night's sleep. Severe asthma attacks can send a person to the ER and even put their life in danger. There's no cure for asthma, but symptoms can be managed with a variety of medications and by avoiding asthma triggers.

Asthma is extremely common in the United States. About 8% of adults and 7% of children — roughly 25 million Americans — have asthma (via the Asthma and Allergy Foundation of America). It's the most common chronic condition in children. Interestingly, boys are more likely than girls to have asthma, but in adulthood, women are more likely than men to have the condition. Each year, asthma attacks lead to 1.6 million ER visits, and it's estimated that asthma costs individuals approximately $3,266 annually.

Asthma and your lungs

To better understand asthma, you need to know a little bit about lung anatomy and function. 

As the Asthma and Allergy Foundation of America explains, every time you take a breath, air moves from your nose or mouth down a tube at the front of your neck called the trachea (windpipe). As it reaches your lungs, the trachea divides into two main "branches" called bronchial tubes. The bronchial tubes then divide into smaller airways (bronchioles). At the end of each bronchiole are tiny balloon-like sacs called alveoli. This network of airways resembles an upside-down tree. The alveoli are where gas exchange happens: Oxygen is transported into the blood and carbon dioxide is transported out of the blood back into the lungs, where it can be exhaled. There are tiny muscles surrounding your airways that control their expansion and constriction as you breathe in and out.

According to WebMD, "people with asthma have sensitive airways that tend to overreact and narrow when they come into contact with even slight triggers." When a person with asthma has an asthma attack, their lungs can be negatively affected in several ways. The bronchial tubes become inflamed, which causes swelling and makes it harder for air to pass through. The muscles surrounding the tubes can also tighten, similarly restricting the ability of air to pass through. Airflow is also hampered by increased mucus production inside the tubes.

Asthma symptoms

All this overreaction in the lungs makes it difficult to breathe during an asthma attack. The exact symptoms, however, will vary from person to person. They include shortness of breath, wheezing when exhaling (especially common in children with asthma), chest tightness and pain, and coughing (via the Mayo Clinic). 

These symptoms may be worse at night or when a person has a cold, the flu, or another respiratory virus. If someone's symptoms become more frequent or severe or they need to use a rescue inhaler more often, these are signs that the asthma is probably getting worse and not being managed sufficiently well. If you experience frequent coughing of wheezing that lasts more than a few days, it's important to visit a doctor to see if you have asthma. The earlier asthma is diagnosed and managed, the less likely it is that long-term lung damage will occur or that the asthma will worsen.

WebMD notes that even in the same individual, symptoms can vary from one asthma attack to another or evolve gradually over time. Symptoms may be mild during some attacks but severe during others. Mild asthma attacks are more common and the airways usually open within a few minutes to a few hours. Severe asthma attacks last longer and require medical intervention. Still, it's important to recognize and adequately address even mild attacks.

Classifying asthma

Doctors classify asthma based on the frequency and severity of symptoms, and this classification helps determine the best course of treatment. There are four categories of asthma (via Medscape). In the first, intermittent asthmas, symptoms are present less than twice a week and nighttime symptoms occur less than twice a month. Flare-ups are brief, although the intensity may vary. In terms of lung function (as measured with specialized medical equipment), those with intermittent asthma generally have results that are close to normal, with little variability from day to day.

In mild persistent asthma, symptoms are present three to six times a week and nighttime symptoms occur three to four times a month. Flare-ups may affect daily activities, but lung function tests are close to normal. In moderate persistent asthma, symptoms occur daily and nighttime symptoms are present five or more times a month. Lung function is farther from normal and varies more substantially. In severe persistent asthma, symptoms are continually occurring and frequently cause problems at night. Lung function is significantly affected.

Asthma can also be categorized based on how easy it is to control. Mild asthma can be managed with medication on an as-needed basis when symptoms arise or with low-dose daily medication. Moderate asthma requires more powerful medications to keep it under control, but at a relatively low dose. Severe asthma either requires higher doses of these medications or can't be controlled at all.

Asthma triggers

But what causes attacks of asthma symptoms in the first place? For those with asthma, the lungs overreact to things that usually don't bother other people's lungs (or at least not to the same degree). Everyone's asthma triggers are different, explains the Asthma and Allergy Foundation of America. Some people may only have one, while others may have many. It's important that people with asthma figure out their triggers so they can avoid them.

Allergies are a major trigger for asthma. Common allergens include pollen, pet dander, mold, and dust mites. But it's important to note that not all people with asthma have allergies, and not everyone with allergies has asthma. Airborne irritants such as cigarette smoke, wood smoke, smog, dust, chemical fumes, and strong fragrances can also trigger an asthma attack. Crying, yelling, laughing, and experiencing other strong emotions can bring on symptoms. Certain medications, including aspirin, NSAIDs, and blood pressure drugs known as beta blockers, can be triggering for some. 

In addition, a number of medical conditions can worsen asthma. These include respiratory infections, food allergies, sleep apnea, nasal polyps, and pregnancy. Even the weather — particularly cold air, dry wind, sudden changes in temperature, and thunderstorms — can bring on symptoms.

Exercise-induced asthma

There's one other asthma trigger that's incredibly common: exercise (per the Cleveland Clinic). 

While physical activity is essential for good health, for those with exercise-induced asthma (also known as exercise-induced bronchoconstriction, exercise-induced bronchospasm, or sports-induced asthma) it can trigger airway inflammation and tightening. An estimated 90% of people with asthma will experience symptoms while or after exercising. However, exercise-induced asthma is also prevalent among individuals with no other asthma triggers and affects about 10% of the general population. Counter to what you might expect, exercise-induced asthma is more common among elite athletes like Olympians than it is among the "weekend warrior" types.

Symptoms usually resolve after about half an hour of rest, but some individuals may have symptoms that return up to 12 hours after exercising. These delayed effects are known as "late phase" symptoms and can take up to 24 hours to go away. The sports most likely to trigger asthma are those in which there's sustained, high levels of exertion (such as distance running and soccer) and those that are played in cold environments (such as skiing or ice hockey). Less rigorous forms of exercise (such as walking or yoga), those that require only short bursts of exertion followed by periods of inactivity (such as baseball), and those played in a warm, moist environment (such as swimming) are less likely to cause a flare-up.

The underlying cause of asthma

Many triggers can spark a flare-up of asthma symptoms, but what causes the condition to begin with? Why do some people's lungs overreact so strongly to things that are generally benign? Why do some people with allergies only get watery eyes or a runny nose, while others have an asthma attack? 

Unfortunately, the exact cause of asthma is unknown (via the American Lung Association). Experts believe the condition is the result of multiple factors working together. Some respiratory infections early in life may increase an individual's chances of getting asthma. A lung infection in infancy or early childhood may cause inflammation and damage to still-developing lung tissue, impacting lung function for the long haul. Other infections early in life, as well as exposure to certain allergens and irritants, also make asthma more likely. When you're young, your immune system is still maturing and figuring out how to properly recognize and respond to threats. If it mistakenly overreacts to something it encounters, it may create a dangerous precedent that it would continue to follow.

Genetics also play a key role in asthma, but it's not as simple as whether or not an individual has one particular gene. In fact, according to a 2015 paper in the European Clinical Respiratory Journal, researchers have identified over 100 genes that play a role in asthma development. Asthma tends to run in families: The closer you're related to someone with asthma, the more likely you have it, too.

How is asthma diagnosed?

An asthma diagnosis is made based on a number of factors and tests. According to the Mayo Clinic, a diagnosis typically begins with an individual visiting their doctor because they have persistent symptoms such as wheezing and coughing. The first step is a thorough medical history, during which the doctor asks the person about their symptoms, family history of asthma, possible environmental exposures, and other medical conditions. A physical exam, including listening to the lungs with a stethoscope, is the next step.

There are several tests doctors can use to gauge lung function. The most commonly used is spirometry, in which a person exhales forcefully into a tube connected to a device that can measure both the volume of air and the speed at which it was exhaled. If your spirometry results are normal or close to it, doctors may do a challenge test, in which they try to induce asthma symptoms and then do another spirometry reading. A nitric oxide test — in which you exhale into a tube that measures the amount of nitric oxide gas in your lungs — can also help diagnose asthma, since nitric oxide tends to build up in those with the condition. 

If the doctor wants to rule out other possible reasons for your symptoms or suspects that you may have other medical conditions that may be making asthma symptoms worse, a variety of blood tests or imaging of the chest or sinuses may also be done.

Controlling and managing asthma

As the Cleveland Clinic states, asthma can't be cured, but it can be managed. The goal is to adequately control the condition so that a person experiences few or no symptoms and rarely needs to use a rescue inhaler. Well-controlled asthmas means a person can do the things they want to do during the day and their sleep isn't interrupted by asthma symptoms. Managing asthma requires making (and sticking to) an action plan developed with healthcare professionals. The action plan spells out how and when asthma medication should be used and what to do if asthma symptoms seem to be getting worse and when emergency care is necessary.

An individual's action plan also includes identifying their unique triggers and avoiding them as much as possible or taking measures to minimize their impact if they can't be avoided (via the Mayo Clinic). Individuals with asthma may also be asked to track their symptoms in a symptom diary for better long-term monitoring of how well the asthmas is being controlled. People with asthma may also need to regularly track their lung function at home using a peak flow (PF) meter.

Long-term asthma control medications

There are a number of medications that can be used to control asthma. For many people, the most important of these are long-term control medications (via the Mayo Clinic). These are used to control chronic symptoms. They're taken daily, even if an individual isn't experiencing any active symptoms.

Inhaled corticosteroids are the most commonly used long-term control medication. These anti-inflammatory drugs reduce swelling and constriction in the airways. Leukotriene modifiers are another option for long-term control. They block the action of leukotrienes, immune system chemicals that trigger the symptoms of asthma. Long-acting beta agonists (LABAs) can open airways and reduce swelling for approximately 12 hours, and are most commonly used at night. However, because of safety concerns, they're now only prescribed in a combination inhaler that also contains a corticosteroid. Theophylline is another bronchodilator (airway opener), but this one is taken in pill form and generally used for more mild asthma.

Most long-term control medications (as well as quick-relief medications) are inhaled. According to Johns Hopkins Medicine, the most common delivery method is a metered-dose inhaler (MDI). An MDI delivers a set amount of aerosolized medication that is inhaled into the lungs. Dry powder or rotary inhalers contain the medication in powder form and are activated by a person's breath. For those who have difficulty using inhalers or have severe asthma, a nebulizer may be needed. This machine sprays a fine, liquid mist of medication into a mouthpiece or a mask.

Quick-relief and rescue medications

Quick-relief medications, also known as rescue medications, are used on an as-needed basis to prevent an imminent asthma attack or treat one that's already underway (perthe Mayo Clinic). If an individual with asthma is exposed to one of their triggers, they may use a quick-relief inhaler to prevent a flare-up. For example, people with exercise-induced asthma may use quick-relief medication right before they work out. For those with only mild, intermittent symptoms, quick-relief medications may be all that's needed to keep their asthma well-controlled.

These medications open the airways by relaxing the small muscles around the bronchial tubes. They take effect within minutes but only last four to six hours. The most commonly used quick-relief medications are short-acting beta agonists such as albuterol and levalbuterol. Ipratropium is a bronchodilator that's usually prescribed for emphysema or chronic bronchitis, but is also sometimes used with asthma patients. For particularly severe asthma attacks, individuals may need to go to the ER, where they'll often receive oral or IV corticosteroids such as prednisone and methylprednisolone.

If an asthma attack is life-threatening, ER doctors may need to intubate. As explained by the Mayo Clinic, in this process, a tube is placed down the throat into the upper airway. A machine pumps oxygen into the lungs and removes carbon dioxide. This gives doctors time to bring the asthma under control using quick-relief drugs.

Allergy medications and biologics

For those with allergy-induced asthma, addressing the underlying allergy is critical. Per the Mayo Clinic, there are a variety of over-the-counter and prescription antihistamines and decongestants that come in both pill and nasal spray forms. It's important to note, however, that nonprescription sprays often cause a rebound effect, creating even more inflammation and irritation. Additionally, they aren't substitutes for asthma medication. On the other hand, corticosteroid and cromolyn nasal sprays can reduce inflammation without a rebound effect. Allergy shots are another option. Injections containing small amounts of the allergens that trigger an individual's asthma are given on a regular schedule (usually once a week for a few months, and then once a month for three to five years).

Biologics (drugs derived from natural sources) are another option for allergy-induced asthma (via the Cleveland Clinic). Omalizumab blocks the activity of antibodies that the immune system has created to otherwise harmless airborne substances such as pollen or pet dander. Omalizumab is given as an injection every two to four weeks. Other biologics target cytokines immune molecules that trigger inflammation in allergy sufferers. These biologics include mepolizumab, benralizumab, and reslizumab. While biologics can be very useful for controlling severe allergy-induced asthma, individuals still need to take their regular asthma medication (per the Mayo Clinic).

Risks of asthma medications

Without a doubt, asthma medications save lives and improve the quality of life for millions of people with asthma. But all drugs can potentially cause side effects, and asthma medications are no exception (via Verywell Health). 

Inhaled corticosteroids can cause hoarseness, a sore mouth or throat, and reflex coughs or windpipe spasms. They can also cause thrush, an oral fungal infection. When used long-term, they may cause cataracts or glaucoma, lead to easy bruising, or result in decreased bone density. Children who regularly use corticosteroids may have impaired growth. Oral corticosteroids can cause a host of issues, including those side effects seen with the inhaled versions. In addition, long-term use of oral corticosteroids may lead to weight gain, fluid retention, elevated blood sugar and blood pressure, and type 2 diabetes.

Short- and long-acting beta agonists (SABAs and LABAs) can cause similar side effects, including increased heart rate, headache, dizziness, anxiety, tremors, and a rash. As you'd probably expect, these side effects tend to last longer with LABAs than with SABAs. Both forms of beta agonists, but especially LABAs, can paradoxically cause severe, life-threatening asthma attacks. Leukotriene modifiers may cause an upset stomach, headache, flu-like symptoms, nasal congestion, rash, nausea, and vomiting. Because the biologic omalizumab suppresses parts of the immune system, people taking it may be more prone to infections.

Other treatments and lifestyle medications

Although medication is the cornerstone of asthma control for most people, there are a number of things individuals can do to help their asthma (via the Mayo Clinic). Most importantly, people with asthma should do their best to avoid their triggers. For those with allergy-induced asthma, using an air conditioner and cleaning regularly can help keep indoor air clean. Maintaining an optimal humidity level by using either a humidifier or dehumidifier, as well as covering your nose and mouth when it's cold outside, can help those with certain weather triggers. Animal lovers with pet dander allergies should choose hypoallergenic breeds and make sure pets are regularly bathed and groomed.

Some individuals may turn to alternative medicine for asthma relief. While some remedies may be helpful, they're not a replacement for medication and more research is needed on their efficacy. Breathing exercises can increase awareness of and control over breathing, and may reduce the amount of medication an individual needs to take. Black seed, caffeine, choline, and pycnogenol are natural remedies that may have some impact on asthma.

It's also important the individuals with asthma stay as healthy as possible. This includes getting regular exercise and choosing exercise that doesn't aggravate exercise-induced asthma. Individuals should take extra precautions to avoid respiratory illnesses and manage heartburn, as both may worsen asthma. Maintaining a healthy weight is also critical, as being overweight or obese can also make asthma worse.

Asthma complications

Severe asthma that doesn't respond well to treatment can lead to long-term complications. One of the most serious is airway remodeling. As Healthgrades explains, airway remodeling is the result of years of chronic inflammation in the lungs and "is a process that changes the structure of the airways. It leads to bronchial wall thickening, narrowing of the air passages, and other physical changes that can be permanent." These structural changes make it harder to breathe. Severe asthma can make daily life difficult. Healthgrades notes that about 60% of asthma patients "report their disease limits their daily activities and physical activities."

If asthma is severe or not adequately controlled, it can be deadly. According to the Asthma and Allergy Foundation of America, about 10 people a day (more than 3,500 a year) die from asthma in the United States. In many cases, these deaths could have been avoided with proper treatment. Rates of asthma deaths are heavily influenced by age and gender. Adults are five times more likely to die from asthma than children, and adult women are more likely to die of asthma than adult men (though in childhood, boys are more likely to die than girls).