Asthma: Types, causes, and diagnosis

Asthma: Types, causes, and diagnosis

Asthma is a chronic disease with an effect on the airways. This causes wheezing, which can make breathing difficult. Some triggers include allergic or irritant exposure, viruses, exercise, emotional stress and other factors.

Asthma causes the internal walls of the airways, or the bronchial tubes, to swell and become inflamed.

The airways will swell during an asthma attack, the muscles around them will contract and it is hard for air to pass in and out of the lungs.

Around 7.9 percent of people in the United States had asthma in 2017. There are several forms of asthma and it may induce asthma or trigger an acute attack by many factors.

This article looks at the types, causes, and triggers of asthma, and how it is diagnosed by a doctor.

What is asthma?

A man suffering from asthma
A person with asthma may experience symptoms when they exercise.

Asthma is a condition which affects the airways in the long term. It involves inflammation and narrowing within the lungs which limits the supply of air.

A person with asthma may experience:

  • tightness in the chest
  • wheezing
  • breathlessness
  • coughing
  • increased mucus production

When the symptoms get severe an asthma attack occurs. Attacks can start suddenly, and can range from life-threatening to mild.

Swelling in the airways can in some cases prevent the oxygen from reaching the lungs. This means oxygen is unable to penetrate the bloodstream or reach vital organs. Those experiencing severe symptoms therefore need urgent medical attention.

A doctor may prescribe appropriate treatments, and advise a person on the best ways to manage their symptoms of asthma.


Asthma can occur in many ways, and for many different reasons, but often the triggers are the same. These contain airborne pollutants, viruses, pet dander, cigarette smoke and mold.

The following sections list several common types of asthma.

Childhood asthma

Asthma is the most common chronic disease in children. It can occur at any age, but it is significantly more common in children than in adults.

Children aged 5–14 years were most likely to have an asthma in 2017. The condition affects 9.7 percent of people in this age group. This also affected 4.4 percent of children aged 0–4 years.

In the same year, 7.7 per cent of people aged 18 and over were affected by asthma.

Some common triggers of childhood asthma, the American Lung Association says, include:

  • respiratory infections and colds
  • cigarette smoke, including secondhand tobacco smoke
  • allergens
  • air pollutants, including ozone and particle pollution, both indoors and outside
  • exposure to cold air
  • sudden changes in temperature
  • excitement
  • stress
  • exercise

If a child begins developing asthma it is important to seek medical care, because it can be life-threatening. A doctor may give advice on some of the best ways to manage that condition.

In some cases, as the child reaches adulthood asthma can improve. It’s a lifelong condition for many people though.

Adult-onset asthma

Asthma can develop at any age, even adulthood. Adults are more likely to have chronic symptoms than children according to one 2013 report.

Some factors affecting the risk of developing an adult asthma include:

  • respiratory illness
  • allergies and exposure to allergens
  • hormonal factors
  • obesity
  • stress
  • smoking

Occupational asthma

Occupational asthma results from the on-the-job reaction to an allergen or irritant.

In those with sensitivity or allergy, allergens can cause asthma at the following workplaces.

  • 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:

The work environment of an individual can cause a return of childhood asthma or the onset of adult-onset asthma.

Difficult-to-control and severe asthma

Research suggests that about 5–10 percent of asthma patients have severe asthma.

Some people experience severe symptoms for reasons not directly related to asthma. They may not have learnt the right way to use an inhaler, for example.

Others experience severe refractory asthma. In these cases, the asthma does not respond to treatment — even with high doses of medication or the proper use of inhalants. According to one study in 2015, this type of asthma may affect 3.6 percent of people with the condition.

Eosinophilic asthma is another form of asthma that, in extreme cases, does not respond to the normal medications. While some people with eosinophilic asthma cope with regular asthma medications, others may benefit from different “biologic” therapies. One type of biological medication reduces the number of eosinophils involved in an allergic reaction that can trigger asthma, which is a type of blood cell involved.

Seasonal asthma

This form of asthma occurs at certain times of the year in response to allergens that are present only in the surrounding environment. For example, cold winter air, or spring or summer pollen may trigger seasonal asthma symptoms.

People with seasonal asthma still have the condition for the rest of the year, but there are usually no symptoms that they experience.

However, asthma doesn’t always originate from an allergy.

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 could be both causes and triggers, such as sensitization to an allergen. Some other sections are listed below.


Smoking during pregnancy appears to increase the likelihood that the fetus will develop asthma later in life according to one study. Some women often suffer worsening symptoms of asthma when they are pregnant.


One study from 2014 indicated that people with obesity tend to have higher rates of asthma than those without it. The authors note that children with obesity who lost weight had also seen changes in their symptoms of asthma in one study.

There is now a growing body of evidence indicating that both conditions require a chronic inflammatory response, and that may explain the link.


Allergies develop when an individual’s body becomes sensitized to a particular substance. If the sensitization has occurred, each time they come into contact with the substance, the individual will be susceptible to an allergic reaction.

Not every asthma person has an allergy but there is often a connection. Exposure to specific allergens can trigger symptoms in people with allergic diseases.

One study in 2013 found that 60–80 per cent of children and young asthma adults are sensitive to at least one allergen.

Smoking tobacco

According to American Lung Association, cigarette smoking can trigger asthma symptoms.

Asthma can also cause damage to the lungs, even without smoking. This can increase the risk of developing various lung conditions related to tobacco, such as chronic obstructive pulmonary disease, and may aggravate the symptoms.

Environmental factors

Air pollution can affect the development and triggers of asthma, both inside and outside of the home.

Some allergens inside the home include:

  • mold
  • dust
  • animal hair and dander
  • fumes from household cleaners and paints
  • cockroaches
  • feathers

Other triggers in the home and outdoors include:

  • pollen
  • air pollution from traffic and other sources
  • ground-level ozone


Stress can cause symptoms of asthma, but so can many other emotions. Joy, anger, excitement, laughter, crying and other emotional reactions all can trigger an asthma attack.

Scientists have also found evidence to suggest that people with mental health conditions such as depression may be more likely to experience asthma.

Others have proposed that long-term stress may result in epigenetic changes contributing to chronic asthma.

Genetic factors

There is proof that asthma occurs in families. Recently, scientists have mapped out some of the genetic changes that may play a role in its development.

In some cases the responsibility lies with epigenetic changes. These occur when an environmental factor is altering a gene.

Hormonal factors

Around 5.5% of males and 9.7% of females experience asthma. Additionally, symptoms may vary in the menstrual cycle depending on the reproductive stage and point of a female.

For example, symptoms can worsen during menstruation during their reproductive years , compared with other times of the month. Doctors call this asthma perimenstrual. Asthma symptoms can however improve during menopause.

Some scientists suggest that hormonal activity can affect immune function, resulting in the airways becoming hypersensitive.

People with sporadic asthma can also only experience symptoms occasionally.


A doctor will ask the person about their symptoms, the medical history of their family and their personal history of medicine. They may also conduct a physical exam, and can conduct several other tests.

They will also note when the doctor makes their diagnosis whether the asthma is mild, intermittent, moderate or severe. They’ll also try to pinpoint the type.

People can keep a log of their symptoms and possible causes to assist the doctor in making a precise diagnosis. This should include information on potential workplace irritants.

The sections below discuss some other tests a doctor may conduct to help diagnose asthma.

Physical exam

The doctor concentrates on the upper respiratory tract, chest, and skin. They’ll listen for wheezing signs that may 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

They will also check the skin for signs of eczema or hives.

Asthma tests

A lung function test may also be performed by your doctor to assess how well the lungs work.

A test on spirometry is one example of a test on lung function. 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.

Then the doctor compares these results with those of a person who is similarly aged but who has no asthma.

The doctor may then give the person a bronchodilator drug — to open the air passages — to confirm the diagnosis, and repeat the test. The person may have asthma if those second results are better.

However, this test may not be suitable for young children. Instead, the doctor may prescribe 4–6 weeks of asthma medicines, and monitor any changes in their symptoms.

Other tests

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.

Tests to rule out other conditions. Sputum tests, X-rays, and other tests can help rule out sinusitis, bronchitis, and other conditions that can affect a person’s breathing.


Asthma is a chronic inflammatory condition that causes swelling in the airways. It can affect people of any age, and may range from mild to severe symptoms.

Effective treatment that can help a person live a full and active asthma-life is available in most cases.


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, especially if they have severe asthma as children, are at high risk of developing COPD.

Emphysema, on the other hand, is not asthma-related although its symptoms may be similar. Cigarette smoking almost always causes this.

Answers represent our medical experts’ opinions. All material is purely informational and medical advice should not be considered.