Asthma is a condition in which your airways narrow and swell and may produce extra mucus. This can make breathing difficult and trigger coughing, a whistling sound (wheezing) when you breathe out and shortness of breath.

For some people, asthma is a minor nuisance. For others, it can be a major problem that interferes with daily activities and may lead to a life-threatening asthma attack.

Asthma can't be cured, but its symptoms can be controlled. Because asthma often changes over time.

Symptoms

Asthma symptoms vary from person to person. You may have infrequent asthma attacks, have symptoms only at certain times — such as when exercising — or have symptoms all the time.

Asthma signs and symptoms include:

Shortness of breath

Chest tightness or pain

Wheezing when exhaling, which is a common sign of asthma in children

Trouble sleeping caused by shortness of breath, coughing or wheezing

Coughing or wheezing attacks that are worsened by a respiratory virus, such as a cold or the flu

Signs that your asthma is probably worsening include:

Asthma signs and symptoms that are more frequent and bothersome

Increasing difficulty breathing, as measured with a device used to check how well your lungs are working (peak flow meter)

The need to use a quick-relief inhaler more often

For some people, asthma signs and symptoms flare up in certain situations:

Exercise-induced asthma, which may be worse when the air is cold and dry

Occupational asthma, triggered by workplace irritants such as chemical fumes, gases or dust

Allergy-induced asthma, triggered by airborne substances, such as pollen, mold spores, cockroach waste, or particles of skin and dried saliva shed by pets (pet dander)

Seek emergency treatment

Severe asthma attacks can be life-threatening. Work with your doctor to determine what to do when your signs and symptoms worsen — and when you need emergency treatment. Signs of an asthma emergency include:

Rapid worsening of shortness of breath or wheezing

No improvement even after using a quick-relief inhaler

Shortness of breath when you are doing minimal physical activity

Trouble breathing

Vocal cord dysfunction

Causes

It isn't clear why some people get asthma and others don't, but it's probably due to a combination of environmental and inherited (genetic) factors.

Asthma triggers

Exposure to various irritants and substances that trigger allergies (allergens) can trigger signs and symptoms of asthma. Asthma triggers are different from person to person and can include:

Airborne allergens, such as pollen, dust mites, mold spores, pet dander or particles of cockroach waste

Respiratory infections, such as the common cold

Physical activity

Cold air

Air pollutants and irritants, such as smoke

Certain medications, including beta blockers, aspirin, and nonsteroidal anti-inflammatory drugs, such as ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve)

Strong emotions and stress

Sulfites and preservatives added to some types of foods and beverages, including shrimp, dried fruit, processed potatoes, beer and wine

Gastroesophageal reflux disease (GERD), a condition in which stomach acids back up into your throat

Asthma and acid reflux

Risk factors

A number of factors are thought to increase your chances of developing asthma. They include:

Having a blood relative with asthma, such as a parent or sibling

Having another allergic condition, such as atopic dermatitis — which causes red, itchy skin — or hay fever — which causes a runny nose, congestion and itchy eyes

Being overweight

Being a smoker

Exposure to secondhand smoke

Exposure to exhaust fumes or other types of pollution

Exposure to occupational triggers, such as chemicals used in farming, hairdressing and manufacturing

Complications

Asthma complications include:

Signs and symptoms that interfere with sleep, work and other activities

Sick days from work or school during asthma flare-ups

A permanent narrowing of the tubes that carry air to and from your lungs (bronchial tubes), which affects how well you can breathe

Emergency room visits and hospitalizations for severe asthma attacks

Side effects from long-term use of some medications used to stabilize severe asthma

Proper treatment makes a big difference in preventing both short-term and long-term complications caused by asthma.

Disclaimer: Information about this information was collected from Mayoclinic.org.