Asthma means that the inside of your airways are very reactive to things you are allergic to (allergens) or find irritating (irritants), causing the airways to narrow and allow less air to flow to your lungs.  

Common allergens include:

• Dust mites (found in ordinary house dust)
• Pollen from flowers, trees, plants, etc.
• Mold (indoor and outdoor)
• Animal dander (from the skin, hair, or feathers of animals)
• Cockroaches and cockroach droppings
• Certain foods (such as fish, shellfish, peanuts, milk, eggs, soy, wheat, tree nuts)
• Certain food additives, such as sulfites in dried fruit or beverages (wine)
• Certain medicines, such as penicillin, aspirin or other non-steroidal anti-inflammatory drugs such as ibuprofen, and beta-blockers (used to treat heart disease, high blood pressure, and migraine headaches)

(For more information about allergies and allergens, go to Key Point 2.) 

Common irritants include:

• Cigarette smoke
• Air pollution
• Cold air or changes in weather
• Strong odors from painting or cooking
• Scented products

Other things that can provoke asthma symptoms include:

• Exercise
• Viral infection
• Strong emotional expression (such as crying or laughing hard)
• Anxiety and stress
• Gastroesophageal reflux disease, a condition that causes heartburn

All of these things – allergens, irritants, and the others – are often called asthma triggers because they can provoke asthma symptoms.  These symptoms include wheezing, coughing, a feeling of tightness in the chest, and shortness of breath.  If you have these symptoms, you should see your doctor for a thorough examination and diagnosis. 

Normally, this will include:

• A medical history -- you'll be asked questions about
• The asthma symptoms you suffer, such as how often, how severe, and what things seem to provoke or worsen them 
• Allergies or allergy symptoms you have
• Family members with allergies or asthma
• Asthma triggers you may encounter at home or work, such as animals, pollen, tobacco smoke, etc.
• A physical examination, with special attention to the respiratory system (lungs and airways)
• A series of diagnostic tests, which may include:
• Lung function tests to measure various aspects of your breathing, such as:
• Spirometry, a major test for diagnosing asthma, which uses a device called a spirometer to measure the amount of air you can breathe and the rate at which it flows through your airways.  The test may include using a medicine that widens narrowed airways, to see if this improves results.   The medicine is inhaled using a device called a bronchodilator (for more information about bronchodilators, go to Key Point 3.) 
• Peak airflow test, which uses a hand-held device called a peak flow meter to measure how fast and how much you can exhale.  People with asthma often use peak flow meters at home to monitor their condition.
• Allergy tests (for more information about allergy tests, go to Key Point 2.) 
• Trigger tests to see how you react to known asthma triggers.  One trigger test involves inhaling a substance called methacholine that constricts the airways of people with asthma; test results that worsen after inhaling methacholine suggest a diagnosis of asthma.
• Exercise challenge tests to see how your respiratory system responds to physical activity.
• Asthma medication trials, to see if your symptoms improve when you take samples of asthma medicines; improvement suggests a diagnosis of asthma.
• Additional tests to rule out other conditions that can cause asthma-like symptoms, such as heart disease, other lung conditions, and gastroesophageal reflux (which causes heartburn).
• Chest x-ray.
• Blood and saliva tests.

Because a person's symptoms can vary from one time to another, an immediate diagnosis may not be possible.  But the eventual diagnosis will indicate if you have asthma and how severe it is.  Generally, asthma cases are classified as being in one of four levels of severity, depending on how often symptoms occur when the condition is not treated:

• Mild intermittent asthma: symptoms happen in general twice a week or less, and at night twice a month or less.
• Mild persistent asthma: symptoms happen in general more than twice a week, but no more than once a day, and at night more than twice a month;  asthma attacks may affect activity.
• Moderate persistent asthma: symptoms happen in general every day, and at night more than once a week; asthma attacks may affect activity
• Severe persistent asthma: symptoms happen in general throughout the day on most days, and often at night; asthma attacks most likely affect and limit activity.

The treatment prescribed will depend on the severity level.  For information about treating asthma, go to Key Point 3.