Asthma can develop at any age, but most people with asthma are diagnosed in childhood.

There are many ways that a doctor evaluates and diagnoses people with asthma — but a chest X-ray ​is mostly used when someone is hospitalized or treated in an emergency department because of a severe asthma attack.

Learn when an asthma X-ray may be used, what other methods are used to diagnose asthma (especially early in life), and available treatments.

X-rays send small amounts of electromagnetic radiation through your chest to create images of the bones and tissues.

In terms of an asthma diagnosis, an X-ray of the chest can provide a doctor with basic images of the lungs and main bronchial tubes (also known as the airways). A chest X-ray may also help a doctor rule out other diseases of the lungs.

Chest X-rays can help a doctor:

  • identify a pneumothorax, which occurs when air leaks into the space between your lung and chest wall
  • check for pneumonia
  • diagnose heart failure

Chest X-rays aren’t the only diagnostic tool for asthma. But these images can help diagnose other conditions with symptoms similar to asthma.

Here are a few examples of chest X-rays from people who have been diagnosed with asthma.

X-rays aren’t typically used to diagnose asthma alone. But a doctor may order a chest X-ray for asthma in the following cases:

  • to identify causes of severe asthmasymptoms that don’t respond to treatment, leading to an asthma attack
  • to evaluate alternative causes of symptoms before diagnosing asthma in young childrenyounger than 5 years old (who might not be able to complete breathing tests)
  • to check for lung damage from conditions like pulmonary fibrosis
  • to help diagnose pneumoniaas a cause of an asthma attack

A chest X-ray can tell if pneumonia or a foreign body in the airway may be causing symptoms similar to asthma.

But lung function tests are the most useful tool to diagnose asthma. A doctor may use a spirometer to assess the amount and pattern of airflow that’s exhaled.

Looking at a person’s medical history and doing a physical exam are both essential in diagnosing asthma. A doctor will typically ask about symptoms that were noticeable early in life, especially in older children and adults, and will also look for other clues that can indicate asthma, such as:

  • recurring episodes of asthma symptoms
  • asthma triggers in your environment
  • personal or family history of allergic conditions

A physical exam alone may not always indicate asthma. Abnormal findings during a physical, such as wheezing, can be a symptom of asthma as well as other respiratory conditions. Other diagnostic tools may need to be used to confirm the diagnosis.

Other tests that can be used to diagnose asthma include:

  • exhaled nitric oxide (FeNO) test: may help detect eosinophilic or allergic asthma
  • allergy tests: help rule out common allergens or allergen-specific antibodies that might trigger your asthma symptoms
  • blood tests: look for inflammatory markers in your bloodstream, such as a complete blood count (CBC) test or test for immunoglobulin E levels
  • exercise tests: can help diagnose exercise-induced asthma
  • computed tomography (CT) scans: help diagnose pneumonia, pulmonary fibrosis and bronchiectasis

Chest X-rays may be conducted directly at your doctor’s office, an outpatient clinic, or a hospital.

At your appointment, you’ll be asked to change out of your clothes from the waist up and to put on a gown. You’ll also need to remove jewelry, watches, and other metallic items that may interfere with the X-ray.

Here’s what usually happens during a chest X-ray for asthma:

  1. A technician will have you stand or sit in front of the X-ray machine.
  2. The technician will instruct you to hold still as they quickly take images with the X-ray machine. They may do this either on the other side of the wall from the procedure room or in a separate room.
  3. Multiple images are taken, with a minimum of one side view and one front view of your chest.
  4. Once the X-rays have been complete, your technician will send them along with a report to the doctor.

Depending on where the images are taken, you may get the results the same day or in the following days (sometimes up to a week).

X-rays use radiation, so there’s a risk that repeated exposure could increase the risk of developing cancer later in life.

But X-rays for asthma carry few short-term risks, as they aren’t typically repeated on a regular basis. A single X-ray to help diagnose asthma is unlikely to pose long-term risks.

Tell a doctor if you’re pregnant or are trying to become pregnant — you may need to wait to have X-rays done. If X-rays are recommended in an emergency, a doctor may consider the benefits of the X-ray against any risks and take extra precautions, such as placing a lead apron over your abdominal area.

Children may also be more susceptible to the effects of radiation from X-rays, especially with exposure from repeated imaging tests. Talk with a doctor about diagnostic options for your child — they may still recommend a chest X-ray if the benefits outweigh the risks, especially if your child is too young to perform a spirometry test.

Once a doctor has diagnosed you with asthma, they’ll recommend treatments that address the causes of your condition as well as the severity of your symptoms.

Treatment may include a combination of the following:

A chest X-ray is the first type of imaging that’s given to many individuals with symptoms of asthma. It’s used to find complications or other causes of wheezing.

In most people with mild cases of asthma, a chest X-ray won’t find any causes for concern. A doctor will likely recommend a combination of tests to help determine the underlying causes so you’re prescribed the right treatments.

Since there’s no cure for asthma, taking prescribed treatments is the best way to address your symptoms while preventing asthma attacks. Call a doctor if your current treatment plan isn’t helping your symptoms.