What Is Asthma? Symptoms & Causes

Asthma is a chronic lung disease that causes inflammation and narrowing of your airways (bronchi), making breathing difficult. It’s a common condition that affects nearly 26 million adults and children in the United States.1

In this article, we’ll discuss what asthma is, its symptoms, and common triggers. Understanding your risk of asthma and the symptoms to look out for can help you get the treatment you need  as quickly as possible. For some people, asthma is manageable, while for others, it can be a life-threatening disease.

What Is Asthma?

Asthma is an inflammatory lung disease that causes your airways to narrow, leading to shortness of breath and other lung symptoms. It’s often a life-long condition that you’ll need to monitor and treat from time to time. For some people, asthma symptoms are mild and typically don’t interfere with their everyday lives — for others, asthma may be a life-threatening condition.2

In asthma, your airways swell and narrow in reaction to an irritating substance or trigger. Some peoples’ lungs also make extra mucus in an attempt to trap substances that set off their asthma symptoms. Long-term inflammation eventually causes thickening of your airways, which can permanently affect your ability to breathe.

What Causes Asthma?

Doctors and researchers aren’t quite sure what causes asthma, but they believe that the immune system plays a role. Normally, your body’s immune system works hard to fight off foreign invaders like bacteria, viruses, and potential allergens to stop you from getting sick.

However, in asthma, your immune system may overreact to certain normally harmless substances you breathe that cause excess inflammation. Substances that cause an allergic reaction are known as allergens. Your lungs may react to specific allergens that cause your airways to become inflamed and narrow, such as pollen, dust, pet dander, or mold.3

Other common asthma triggers include:4

  • Nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen (Motrin®, Advil®) and naproxen sodium (Aleve®) (in a certain subset of patients)
  • Upper respiratory infections, including the common cold
  • Acid reflux or gastroesophageal reflux disease (GERD)
  • Extremely dry or cold air
  • Smog or air pollution
  • Exercise
  • Tobacco smoke

Types of Asthma

There are several types of asthma that can be broken down based on what triggers your symptoms. Most people think of allergic asthma or exercise-induced asthma when they think of this lung condition — however, there are many other triggers to be aware of.

Allergic Asthma

Allergic asthma occurs when your airways react to an allergen, causing an allergic reaction. Your immune system responds to the allergen by releasing a type of antibody known as IgE, which triggers inflammation.3 Most allergens that set off your asthma are also responsible for causing seasonal allergies in the warm months in temperate climates, or year-round allergies indoors. They include:

  • Pollen from trees (spring), grasses (mid-summer), and weeds (late summer through fall until the first frost)
  • Dust and dust mites (tiny insects that eat our normally shedding skin in our beds and upholstered furniture))
  • Pet dander or skin flakes from cats and dogs
  • Mold indoors or outdoors in the fall or damp seasons
  • Cockroaches
  • Other pests including mice and rats

Exercise-Induced Bronchoconstriction

Some people with asthma go about their normal days never experiencing any asthma symptoms. When they start to run, hike, or swim, they become short of breath or wheeze. This is known as asthma or exercise-induced bronchoconstriction (EIB, narrowing of your airways).5

It’s estimated that many people with asthma also have EIB.5 Since you’re likely to breathe heavily during exercise, taking in dry and/or cold air, it’s more likely to irritate your lungs. Pollen, dust, or pollution in the air can also cause irritation.

Occupational Asthma

Occupational asthma develops as the result of exposure to irritating chemicals or substances from your workplace. Most occupational asthma symptoms go away on their own after you avoid your triggers. Dusts, vapors, gases, and fumes from different industries can all irritate the lungs and lead to asthma symptoms.6

The following occupations are more likely to develop occupational asthma:

  • Bakers and those who work in food processing plants (dust from flour, grains, and cereals)
  • Those who work with metals or in refineries (nickel, platinum, chromium)
  • Farmers, veterinarians, and animal trainers (mites, dander, hair, insects)
  • Those who work in plastics and upholstery manufacturing (chemical vapors and dust)
  • Textile workers (dust from textiles and cotton)
  • Those who work in in painting, roofing (isocyanates)

Medication-Induced Asthma

Did you know that taking certain medications can cause asthma symptoms? If you take a pain-relieving nonsteroidal anti-inflammatory drug (NSAID) like ibuprofen (Advil®, Motrin®) or naproxen sodium (Aleve®), or aspirin, you may notice you become short of breath or start wheezing. Other medications used to treat high blood pressure, such as ACE inhibitors and beta-blockers, can also trigger asthma or symptoms that mimic asthma such as coughing (especially ACE inhibitors).7

If you’re taking an NSAID or blood pressure medication and begin experiencing asthma symptoms, talk to your doctor. Do not stop taking your medications without first consulting your doctor.

Risk Factors for Developing Asthma

Some factors can increase your risk of developing asthma. Some of these you can control, while others you can’t. Knowing your risk can help you take extra steps to avoid developing asthma or even triggering an attack if you’re already living with the condition. Examples include:4

  • Having another allergic condition like seasonal allergies (hay fever) or eczema
  • Being overweight or obese
  • Smoking tobacco products, especially long-term
  • Exposure to air pollution, smog, or exhaust fumes
  • Living with or being near someone who smokes (secondhand smoke exposure)
  • Having a parent or sibling who also has asthma
  • Working in a profession that exposes you to chemicals, like manufacturing, farming, or hairdressing

Race and sex also seem to play a risk in developing asthma. According to the Asthma and Allergy Foundation of America, female adults are more likely to have asthma compared to male adults. However, male children are more likely to have asthma compared to female children. Black children and adults are more likely to have asthma compared to white children and adults.1 Notably, individuals of Puerto Rican descent have the highest rate of asthma of all demographic groups, especially compared to other Hispanics.8

Symptoms of Asthma

When you have asthma, your airways swell and make extra mucus, making it hard to breathe. Asthma symptoms can range from mild to severe, depending on each person and any triggers. An asthma flare or episode can last anywhere from a few minutes to several hours or days. Everyone’s symptoms are different, but they can include:9

  • Feeling like you can’t breathe deeply enough or catch your breath (shortness of breath)
  • A wheezing or whistling sound when you breathe
  • Chest pain or tightness, which can feel like something squeezing or sitting on your chest
  • Coughing, which may bring up extra mucus clogging your airways
  • Waking up in the middle of the night feeling short of breath or coughing

Symptoms of an Asthma Attack

When your asthma symptoms are severe and appear suddenly, it’s known as an asthma attack. It’s best to work with your primary care doctor, pulmonologist, or allergist to create an asthma action plan to monitor your symptoms and know when to seek treatment. Your asthma warning signs may be unique to you, so it’s important to learn what your triggers are and how to handle them.

During an asthma attack, your quick-relief or emergency medications might not help. Signs of an asthma attack that require immediate medical attention include:9

  • Severe shortness of breath
  • Having trouble talking, standing, or walking due to shortness of breath
  • Extreme chest pain and tightness
  • Shallow breathing
  • Hunching your shoulders when trying to breathe
  • Abnormal breathing speed (too fast or too slow)
  • Skin sucking into your body around your ribs or neck, known as chest retractions (more common in children than adults)
  • Changes in color around your lips, tongue, eyes, and fingernails — skin may appear blue on lighter skin tones and white or gray on darker skin tones

Diagnosing Asthma

If your doctor believes you have asthma, they’ll likely perform a physical exam and run several tests to measure how well your lungs work. There’s no single test that can diagnose asthma — instead, your doctor will put together your medical history and the results of several tests to make a final diagnosis.

Medical History and Physical Exam

Your doctor will likely start by taking your medical history to learn more about your symptoms and your risk factors. Be sure to tell them if any immediate family members have asthma, seasonal allergies, or other inflammatory conditions or diseases.10 Your doctor will also ask about the triggers that make your symptoms worse. Some questions they may ask include:

  • What medications do you currently take?
  • What is your occupation? Are you exposed to any substances that may trigger your symptoms?
  • Do you have any pets at home, especially if being around them worsens your symptoms?
  • Do your symptoms get worse after eating a certain food?
  • Do you currently smoke, or are you a former smoker?
  • Do your symptoms get worse when exercising?

During your physical exam, your doctor will check your temperature, heart rate, and blood oxygen level to determine whether an infection is causing your symptoms. They’ll also listen to your heart and lungs for any signs of wheezing.

Lung Function Tests

Lung function tests — also known as pulmonary function tests — measure how well you breathe and how well your lungs work.11 Your doctor may use one of several lung function tests to diagnose asthma, including spirometry, a methacholine challenge test, and an exhaled nitric oxide test.


Spirometry is used to measure the amount of air you’re able to breathe in and out. It also measures how quickly you can push air out of your lungs. Spirometry is an important tool for diagnosing many different lung conditions, including asthma, chronic obstructive pulmonary disease (COPD), and lung scarring (pulmonary fibrosis).12

On the day of your spirometry test, your doctor may have you stop taking certain medications or inhalers that can interfere with the results. Don’t smoke for at least 6 hours before your test as well. At the clinic, a technician will place a plastic clip over your nose and a mouthpiece into your mouth that’s connected to a spirometry machine (spirometer). You’ll be asked to breathe in and out of your mouth a few times, breathing as deeply as possible and blowing out as hard and fast as possible.

The spirometer will assess two key meaures of your breathing capacity — forced vital capacity (FVC) and forced expiratory volume (FEV1). Your FVC is how much air you breathe out after taking the deepest breath in. Your FEV1 is the volume of air you breathe out in 1 second.

Your FVC and FEV1 are used to calculate a score and compare you to other people of similar age, sex, height, and weight.. An abnormal score with a lower FVC or FEV1 may point to an asthma diagnosis.

Methacholine Challenge Test

After your initial spirometry test, your doctor may also choose to perform a methacholine challenge test. Once your breathing is measured to establish your normal FVC and FEV1 values, you’ll be given an inhaler containing the drug methacholine. Methacholine causes your airways to narrow, making it harder to breathe.13

Your doctor will give you several small doses of methacholine that increase over time. You’ll use the inhaler (from which you inhale the methacholine) and then measure your breathing with the spirometer until your ability to breathe drops by at least 20 percent. People without asthma aren’t as affected by methacholine as those with asthma. If your breathing ability drops by 20 percent or more at a low concentration of inhaled methacholine during the test, you likely have asthma.

Exhaled Nitric Oxide Test

An exhaled nitric oxide test — also known as a fractional exhaled nitric oxide (FeNO) test — is used to measure the amount of nitric oxide you breathe out.14,15 This is a substance created when there’s a specific type of inflammation in your airways that is suggestive of asthma (eosinophilic inflammation). A FeNO test is similar to a spirometry test but easier to perform. Your nose is closed with a plastic clip, and you breathe into a mouthpiece connected to a specialized machine. You’ll take a deep breath in slowly, then breathe out at a steady rate until the machine beeps.

Complications of Asthma

Many people living with asthma also deal with other complications that impact their quality of life. For those who wake during the middle of the night with asthma symptoms, it can be hard to get a good night’s sleep. You may feel fatigued or sleepy during the day, which can interfere with school, work, and other commitments.4

If you have a bad asthma flare or attack, you may also have to take time off work or school to recover. More severe attacks may even require you to stay in the hospital for a few days to control inflammation in your lungs and bring your breathing back to normal.

Asthma also increases your risk of bacterial and viral lung infections. It can be harder for you to fight off the common cold or bronchitis compared to others without asthma.16

Resources for Living with Asthma

If you or a loved one is living with asthma, there are countless resources available to you to offer support and more information on living with asthma. Feel free to find an online or in-person community or browse these resources to learn more: