Types, causes, and diagnosis of asthma
Asthma causes the inside walls of the airways, or the bronchial tubes, to become swollen and inflamed.
During an asthma attack, the airways will swell, the muscles around them will tighten, and it becomes difficult for air to move in and out of the lungs.
Around 7.9% of people in the United States had asthma in 2017. There are many types of asthma, and several factors can cause asthma or trigger an acute attack.
This article looks at the types, causes, and triggers of asthma, as well as how a doctor diagnoses it.
Learn more about managing asthma here.
What is asthma?
A person with asthma may experience symptoms when they exercise.
Asthma is a long-term condition affecting the airways. It involves inflammation and narrowing inside the lungs, which restricts air supply.
A person with asthma may experience:
- tightness in the chest
- increased mucus production
An asthma attack occurs when the symptoms become severe. Attacks can begin suddenly and range from mild to life threatening.
In some cases, swelling in the airways can prevent oxygen from reaching the lungs. This means that oxygen cannot enter the bloodstream or reach vital organs. Therefore, people who experience severe symptoms need urgent medical attention.
A doctor can prescribe suitable treatments and advise a person on the best ways to manage their asthma symptoms.
Learn more about the signs and symptoms of asthma here.
Asthma can occur in many different ways and for many different reasons, but the triggers are often the same. They include airborne pollutants, viruses, pet dander, mold, and cigarette smoke.
The sections below list some common types of asthma.
Asthma is the most common chronic condition in children. It can develop at any age, but it is slightly more common in children than in adults.
In 2017, children aged 5–14 years were most likely to experience asthma. In this age group, the condition affected 9.7% of people. It also affected 4.4% of children aged 0–4 years.
In the same year, asthma affected 7.7% of people aged 18 years and over.
According to the American Lung Association, some common triggers of childhood asthma include:
- respiratory infections and colds
- cigarette smoke, including secondhand tobacco smoke
- air pollutants, including ozone and particle pollution, both indoors and outside
- exposure to cold air
- sudden changes in temperature
It is vital to seek medical attention if a child starts to experience asthma, as it can be life threatening. A doctor can advise on some of the best ways to manage the condition.
In some cases, asthma may improve as the child reaches adulthood. For many people, however, it is a lifelong condition.
Asthma can develop at any age, including during adulthood. According to one 2013 study, adults are more likely than children to have persistent symptoms.
Some factors that affect the risk of developing asthma in adulthood include:
- respiratory illness
- allergies and exposure to allergens
- hormonal factors
Learn more about adult-onset asthma here.
In the following workplaces, allergens may cause asthma in those with a sensitivity or allergy:
- bakeries, flour mills, and kitchens
- hospitals and other healthcare settings
- pet shops, zoos, and laboratories where animals are present
- farms and other agricultural settings
In the following occupations, irritants can trigger asthma symptoms:
- car repairs and manufacturing
- engineering and metalwork
- woodwork and carpentry
- electronics and assembly industries
- hairdressing salons
- indoor swimming pools
Those with a higher risk include people who:
- have allergic rhinitis
- have a history of asthma or environmental allergies
A person's work environment can trigger a return of childhood asthma or the start of adult-onset asthma.
Difficult-to-control and severe asthma
Research suggests that around 5–10% of people with asthma have severe asthma.
Some people have severe symptoms for reasons that do not relate directly to asthma. For example, they may not yet have learned the correct way to use an inhaler.
Others have severe refractory asthma. In these cases, the asthma does not respond to treatment — even with high dosages of medication or the correct use of inhalers. This type of asthma may affect 3.6% of people with the condition, according to one 2015 study.
Eosinophilic asthma is another type of asthma that, in severe cases, may not respond to the usual medications. Although some people with eosinophilic asthma manage with standard asthma medications, others may benefit from specific "biologic" therapies. One type of biologic medication reduces the numbers of eosinophils, which are a type of blood cell involved in an allergic reaction that can trigger asthma.
Learn more about severe asthma here.
This type of asthma occurs in response to allergens that are only in the surrounding environment at certain times of year. For example, cold air in the winter or pollen in the spring or summer may trigger symptoms of seasonal asthma.
People with seasonal asthma still have the condition for the rest of the year, but they usually do not experience symptoms.
Asthma does not always stem from an allergy, however. Learn more about the difference between allergic and nonallergic asthma here.
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Causes and triggers
Health professionals do not know exactly what causes asthma, but genetic and environmental factors both seem to play significant roles.
Some factors, such as sensitization to an allergen, may be both causes and triggers. The sections below list some others.
According to one study, smoking during pregnancy appears to increase the risk of the fetus developing asthma later in life. Some women also experience an aggravation of asthma symptoms while pregnant.
One article from 2014 suggested that there seem to be higher levels of asthma in people with obesity than those without it. The authors note that, in one study, children with obesity who lost weight also saw improvements in their asthma symptoms.
There is now a growing body of evidence suggesting that both conditions involve a chronic inflammatory response, and this could explain the link.
Allergies develop when a person's body becomes sensitized to a specific substance. Once the sensitization has taken place, the person will be susceptible to an allergic reaction each time they come into contact with the substance.
Not every person with asthma has an allergy, but there is often a link. In people with allergic disease, exposure to specific allergens can trigger symptoms.
One 2013 study found that 60–80% of children and young adults with asthma are sensitive to at least one allergen.
Learn more about allergic asthma here.
Cigarette smoking can trigger asthma symptoms, according to the American Lung Association.
Asthma, even without smoking, can cause damage to the lungs. This can increase the risk of developing various tobacco-related lung conditions, such as chronic obstructive pulmonary disease, and it can make symptoms more severe.
Air pollution, both inside the home and outside of it, can affect the development and triggers of asthma.
Some allergens inside the home include:
- animal hair and dander
- fumes from household cleaners and paints
Other triggers in the home and outdoors include:
- air pollution from traffic and other sources
- ground-level ozone
Stress can give rise to asthma symptoms, but so can several other emotions. Joy, anger, excitement, laughter, crying, and other emotional reactions can all trigger an asthma attack.
Others have suggested that long-term stress may lead to epigenetic changes that result in chronic asthma.
There is evidence to suggest that asthma runs in families. Recently, scientists have mapped out some of the genetic changes that may play a role in its development.
In some cases, epigenetic changes are responsible. These occur when an environmental factor causes a gene to change.
Around 5.5% of males and 9.7% of females have asthma. In addition, symptoms may vary according to a female's reproductive stage and point in the menstrual cycle.
For example, during their reproductive years, symptoms may worsen during menstruation, compared with other times of the month. Doctors call this perimenstrual asthma. During menopause, however, asthma symptoms may improve.
Some scientists believe that hormonal activity may impact immune activity, resulting in hypersensitivity in the airways.
People with intermittent asthma may also have symptoms only some of the time. Learn more about intermittent asthma here.
A doctor will ask the person about their symptoms, their family medical history, and their personal medical history. They will also carry out a physical examination, and they may conduct some other tests.
When the doctor makes their diagnosis, they will also note whether the asthma is mild, intermittent, moderate, or severe. They will also try to identify the type.
People can keep a log of their symptoms and possible triggers to help the doctor make an accurate diagnosis. This should include information about potential irritants in the workplace.
The sections below discuss some other tests a doctor may conduct to help diagnose asthma.
The doctor will focus on the upper respiratory tract, the chest, and the skin. They will listen for signs of wheezing, which can indicate an obstructed airway and asthma.
They will also check for:
- a runny nose
- swollen nasal passages
- any growths on the inside of the nose
The doctor may also carry out a lung function test to assess how well the lungs are working.
A spirometry test is one example of a lung function test. The person will need to breathe in deeply and then breathe out forcefully into a tube. The tube links up to a machine called a spirometer, which shows how much air a person inhales and exhales and the speed at which they expel the air from the lungs.
The doctor will then compare these results with those of a person who is similarly aged but who does not have asthma.
To confirm the diagnosis, the doctor may then give the person a bronchodilator drug — to open the air passages — and repeat the test. If these second results are better, the person may have asthma.
This test may not be suitable for young children, however. Instead, the doctor may prescribe asthma medicines for 4–6 weeks and monitor any changes in their symptoms.
Other tests for diagnosis include:
A challenge test. This test allows a doctor to assess how cold air or exercise affect a person's breathing.
A skin prick. A doctor can use this test to identify a specific allergy.
Asthma is a chronic inflammatory condition that causes swelling in the airways. It can affect people of any age, and the symptoms can range from mild to severe.
In most cases, effective treatment is available that can help a person live a full and active life with asthma.
Learn about some options for treating asthma here.
Can asthma develop into other harmful lung diseases, such as COPD or emphysema?
Asthma is a risk factor for COPD, and people with long-standing asthma have a high risk of developing COPD, especially if they had severe asthma as children.
Emphysema on the other hand, is not related to asthma even though their symptoms may be similar. Cigarette smoking almost always causes this.Marc Meth Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.