Each case of asthma is categorized in two different ways: by what triggers symptoms and by the severity of symptoms. Classifying the type of asthma is part of the process of diagnosing asthma. Knowing what type of asthma you have allows your allergist to recommend the best asthma treatment options for your individual situation.
In all types, symptoms of asthma can include wheezing, shortness of breath, chest tightness, coughing, and trouble breathing. When the only symptom of asthma is a dry cough, it may be referred to as cough-variant asthma.
Symptoms of asthma can be triggered by a wide variety of substances, situations, and underlying health conditions. It is possible to have more than one type of asthma.
Allergic asthma is the most common type of asthma, comprising about 60 percent of asthma cases in the United States. Allergic asthma is most prevalent in early childhood and becomes less prevalent with age. Only about 30 percent of adult-onset asthma cases are allergic asthma.
Allergic asthma is caused by an overreaction of the immune system in response to a normally harmless substance, known as an allergen. Allergens vary widely between people, but some of the most common allergies involved in allergic asthma are to pollen, furry pets, mold, cockroaches, and dust mites.
Some people with allergic asthma are advised to undergo immunotherapy to desensitize the body to the allergens that cause asthma.
Nonallergic asthma is more prevalent in adults, peaking in late adulthood. Nonallergic asthma makes up about 70 percent of cases of adult-onset asthma.
In people with nonallergic asthma, it can be more difficult to identify what triggers symptoms. Nonallergic asthma can be triggered by many different substances and situations, including stress, strong emotions, medications, food additives, cold air or changes in the weather, and air pollution involving nonallergenic irritants such as vehicle traffic emissions or smoke.
Most people with asthma — approximately 90 percent — will experience EIB, also known as exercise-induced asthma. For some people, a cough is the only symptom of EIB.
Anyone, even people without asthma, can become short of breath after strenuous exercise. In people with EIB, exercise triggers bronchoconstriction — the narrowing of airways in the lungs. The result is an attack of asthma symptoms that may begin during physical activity, worsen for a few minutes after activity is stopped, and last for about 30 minutes. Some people with EIB experience milder, late-phase symptoms which start a few hours after exercise and last for up to a day.
People who work in jobs where they are exposed to airborne irritants, such as fumes or dust, may develop occupational asthma. Occupational asthma accounts for 15 percent to 23 percent of adult-onset asthma cases in the U.S.
Other types of asthma may also be worsened by workplace exposure to irritants. Encountering irritants on the job is associated with as many as 15 percent of cases of disabling asthma symptoms.
If your asthma symptoms began when you started a job, improve when you are away from your job, and become worse when you are at work, you may have occupational asthma. Professions identified with a higher risk for occupational asthma include bakers, farmers, laboratory workers, and those who work in the manufacturing of pharmaceuticals, metals, plastics, and wood products.
Chronic obstructive pulmonary disease (COPD) is a pulmonary disorder that can include emphysema and chronic bronchitis. Asthma and COPD are separate lung conditions, and both can make it difficult to breathe. People diagnosed with asthma-COPD overlap syndrome (ACOS) experience the features of both asthma and COPD.
People with ACOS tend to experience more frequent and severe symptoms, as well as reduced lung function. Having both COPD and asthma can complicate diagnosis of breathing problems and lead to one condition or the other being missed. COPD is most commonly diagnosed in people ages 50 to 74 who are current or former cigarette smokers.
Aspirin-exacerbated respiratory disease (AERD) is a condition that causes asthma, sinus problems including nasal polyps, and a sensitivity to aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), such as Ibuprofen and Naproxen. About 9 percent of adults with asthma and 30 percent of those with both asthma and nasal polyps are believed to have AERD.
In people with AERD, taking NSAIDs triggers asthma symptoms, nasal congestion, sinus pain, and sometimes flushed skin, abdominal pain, or vomiting. Drinking alcohol also causes a respiratory reaction in about 75 percent of those with AERD.
Eosinophils are one type of white blood cell that fights infections and parasites in the body. In people with eosinophilic asthma, an excess of eosinophils promotes inflammation in the airways that leads to asthma symptoms. High levels of eosinophils may also play a role in AERD. Eosinophilic asthma can develop at any age, but is most often diagnosed in adults between the ages of 35 and 50. People with eosinophilic asthma do not usually have allergies.
In addition to common asthma symptoms, people with eosinophilic asthma may have chronic nasal and sinus inflammation and nasal polyps. Eosinophilic asthma is often severe. Eosinophilic asthma may be treated with biologic therapy, a class of medications produced using biotechnology and proteins derived from living cells.
Read more about treatment options for asthma.
In addition to categorization by asthma triggers, each case of asthma is classified by the frequency of symptoms and how much they impact the activities of daily life. In adults and children aged 5 or older, doctors will also consider forced expiratory volume (FEV) — the result of a lung function test. FEV measures the amount of air that can be exhaled in a forced breath.
The National Asthma Education and Prevention Program has established the criteria described below for classifying asthma severity.
Intermittent asthma is diagnosed in cases where asthma symptoms:
Mild persistent asthma is diagnosed in cases where asthma symptoms:
Moderate persistent asthma is diagnosed in cases where asthma symptoms:
Severe persistent asthma is diagnosed in cases where asthma symptoms:
The classification of asthma severity is used by health care providers to determine which asthma medications are most appropriate. Your asthma classification can change over time. It is important to remember that it is possible to have a severe asthma attack no matter how your asthma is classified.