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The Asthma and Allergy Foundation of America thanks Circassia for sponsoring this blog post.

Asthma is a chronic disease that causes your airways to be inflamed. The most common symptoms of asthma are coughing, shortness of breath, wheezing and chest tightness. But there are other diseases that can have the same symptoms of asthma. For your doctor to make the right diagnosis, it is important to know if your airways are inflamed.

To diagnose asthma, your doctor will ask you about your medical history, give you a physical exam and have you take some breathing tests. These are called lung function tests.

What Is FeNO Testing?

One type of lung function test measures how much inflammation you have in your lungs. It’s called a FeNO test. FeNO stands for fractional exhaled nitric oxide. If your lungs are inflamed, you will have nitric oxide in your breath. A FeNO test tells your doctor if and how much inflammation is in your lungs by measuring nitric oxide.

The test is simple and non-invasive. It’s easy enough for both children and adults to do. Your doctor may have you take the test occasionally to track your FeNO levels.

Why Is It Important to Check FeNO levels?

If you already have already have asthma, tracking your FeNO levels:

  • Determines if your current management plan is working properly and how your medicines may need to be increased or reduced
  • May identify what type of asthma you have
  • Can track your airway inflammation over time
  • Can tell your doctor if you have been taking your medicines correctly

If you have not been diagnosed with asthma, a FeNO test:

  • Can support your asthma diagnosis
  • Helps your doctor know how well you may respond to corticosteroids
  • Can rule out other conditions that have symptoms similar to asthma

Should I Get a FeNO Test?

Talk to your doctor about having a FeNO test if:

  • You have respiratory symptoms that won’t go away but you don’t know if you have asthma
  • You have asthma but your medicines and treatment plan aren’t reducing your symptoms

FeNO testing can be important when it comes to creating an effective asthma treatment plan. Download our handout on FeNO testing to learn more.


It is important to stay up-to-date on news about asthma and allergies. By joining our community and following our blog, you will receive news about research and treatments. Our community also provides an opportunity to connect with other patients who manage these conditions for support.



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