Cystic Fibrosis vs. Asthma: What Are the Differences?

Table of Contents
View All
Table of Contents

Cystic fibrosis (CF) is a rare genetic condition that affects the way the body produces mucus. While it mainly affects the respiratory tract, causing difficulty breathing, it also affects other body organs.

Asthma is a condition in which the airways become narrowed and inflamed. Asthma causes breathing difficulty but does not affect other organs of the body. The underlying causes of asthma are varied and not completely understood.

While cystic fibrosis and asthma are both respiratory illnesses that have some overlapping symptoms, the two conditions are very different. This article discusses the similarities and differences between CF and asthma, including symptoms, causes, diagnosis, treatment, and prevention.

a little girl with cystic fibrosis using a nebulizer at home

Nikodash / Getty Images

Is There a Link Between Cystic Fibrosis and Asthma?

Cystic fibrosis and asthma are both respiratory illnesses, meaning they both affect the lungs. Approximately 19% of people with cystic fibrosis also have asthma, but the majority of people who have asthma do not have cystic fibrosis, which is a rare genetic condition.

What Is Cystic Fibrosis?

Cystic fibrosis is a rare genetic condition caused by a mutation in the CFTR gene, which is responsible for regulating chlorine. The mutation affects the production of mucus and sweat in the body, leading to extremely thick and sticky mucus. This thick, sticky mucus can clog the airways, causing breathing difficulties.

CF also affects the pancreas and can make it difficult for people with CF to absorb fat and certain nutrients properly.

How Common Is Cystic Fibrosis?

Approximately 40,000 people (adults and children) in the United States live with CF.

What Is Asthma?

Asthma is a chronic respiratory condition that causes the airways to become inflamed and narrowed, restricting the amount of air that can move through them. While there is likely a genetic component to asthma, its causes are not fully understood.

Some people have asthma symptoms that are triggered by allergens (substances that can trigger an allergic response in some people) or chemicals in the air, while some may experience symptoms only while exercising. The severity of symptoms also greatly varies between individuals.

Prevalence of Asthma

An estimated 25 million people in the United States have asthma.


Though CF and asthma are separate conditions, they share some overlapping symptoms.

Cystic Fibrosis

Common symptoms of CF include:

  • Persistent coughing with mucus
  • Wheezing
  • Shortness of breath
  • Nasal polyps (noncancerous growths in the lining of the nasal passages and sinuses)
  • Frequent sinus infections or lung infections
  • Abnormal growth or difficulty gaining weight
  • Salty skin
  • Abnormal bowel movements
  • Clubbed fingertips and toes
  • Male infertility
  • Rectal prolapse (part of the large intestine slips out of its normal position)


Asthma shares some of the above symptoms, including:

  • Coughing
  • Shortness of breath
  • Wheezing

Some people with asthma may also experience nasal polyps, frequent sinus infections, or lung infections, depending on the underlying cause of their asthma.


Their causes are another differentiator between these two conditions.

Cystic Fibrosis

Cystic fibrosis is an inherited genetic condition. The parents of individuals who inherit CF each have one copy of a mutated gene. Both parents must pass this mutation on to the child in order for the child to get CF. People who have only one copy of the faulty gene do not have CF, but are known as carriers.

The mutated gene, CFTR, is responsible for making a protein that regulates chlorine and leads to the abnormal production of sweat and mucus in individuals who have CF.


The underlying causes of asthma are not as well understood as those of CF, although asthma may run in families.

Various triggers can produce asthma symptoms for different individuals. Common triggers include allergens, air pollution or other chemical inhalants, exercise, and respiratory infections.


Cystic fibrosis and asthma are diagnosed using different tests.

Cystic Fibrosis

In the United States, most newborns are screened for cystic fibrosis shortly after birth. This involves taking a small drop of blood from the baby's heel, which is then tested for several genetic conditions, including CF.

If CF is not detected during newborn screening, several other tests can be used to help diagnose the condition, including:

  • Sweat tests, which measure the chloride levels in sweat
  • Other blood tests that look for a mutated CFTR gene
  • Chest X-rays and lung function tests, which may point to a CF diagnosis but cannot be used on their own


If your healthcare provider suspects asthma based on your reported symptoms and physical examination, they may order some of the following pulmonary function tests to help confirm a diagnosis:

  • Spirometry
  • Peak airflow
  • FeNO (exhaled nitric oxide testing)
  • Provocation tests

Other testing, such as allergy testing, may be used to determine the underlying causes of asthma.


Cystic fibrosis and asthma are treated using different methods.

Cystic Fibrosis

There is no cure for cystic fibrosis, but several treatments can maintain a person's health. Some of these treatments are:

  • Medications used to treat symptoms and complications of CF, which include antibiotics to treat infections, mucus thinners, bronchodilators and other inhaled medications, and CF transmembrane conductance regulator modulators, including elexacaftor, ivacaftor, tezacaftor, and lumacaftor
  • Working with a respiratory therapist to keep the lungs clear through special breathing and coughing techniques or chest physical therapy
  • Surgery, such as a lung transplant, for some individuals


Asthma is typically treated by:


Though cystic fibrosis and asthma are both respiratory conditions, they are very different illnesses. CF is a rare inherited disorder, while asthma has many causes. They are diagnosed using different tests, and newborns are screened for CF following birth. However, the conditions share some symptoms, including coughing, wheezing, and shortness of breath.

CF is treated with various medications, breathing exercises, chest physical therapy, and potentially surgery. Asthma is treated using inhaled corticosteroids, biologics, bronchodilators, and avoiding triggers.

A Word From Verywell

Cystic fibrosis and asthma are health conditions that can significantly impair your quality of life. However, symptoms and complications can be greatly reduced with treatment and monitoring. Work with your healthcare team to develop an effective treatment plan you can stick with.

Frequently Asked Questions

  • Is cystic fibrosis a contagious disease?

    No. Cystic fibrosis itself is not a contagious illness. However, people with CF can catch infections from other people with CF. Patients with CF are encouraged to maintain a certain distance from other CF patients.

  • Does asthma cause fibrosis?

    No, asthma does not cause fibrosis, even though someone who has fibrosis of the lungs may have similar symptoms to someone who has asthma.

  • Is there a cure for cystic fibrosis?

    No. There is currently no cure for cystic fibrosis. However, while CF used to be considered a terminal illness, with most people dying in infancy or childhood, many people with CF now live to adulthood.

  • Is asthma a chronic lung disease?

    Yes, asthma is a chronic lung disease. However, some people may have decreased symptoms over time. It's also possible for people to "grow out of" asthma.

  • What can cystic fibrosis be mistaken for?

    Primary ciliary dyskinesia (PCD) and Shwachman-Diamond syndrome may cause similar symptoms and be mistaken for cystic fibrosis.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Nielsen AO, Qayum S, Bouchelouche PN, Laursen LC, Dahl R, Dahl M. Risk of asthma in heterozygous carriers for cystic fibrosis: a meta-analysisJournal of Cystic Fibrosis. 2016;15(5):563-567. doi:10.1016/j.jcf.2016.06.001

  2. Cystic Fibrosis Foundation. About cystic fibrosis.

  3. Asthma and Allergy Foundation of America. Asthma facts.

  4. Asthma and Allergy Foundation of America. What are the symptoms of asthma?.

  5. American Lung Association. What causes asthma.

  6. Cystic Fibrosis Foundation. Newborn screening for CF.

  7. Asthma and Allergy Foundation of America. Asthma diagnosis.

  8. National Heart, Lung, and Blood Institute. Cystic fibrosis treatment.

  9. Cloutier MM, Baptist AP, Blake KV, et al. 2020 focused updates to the asthma management guidelines: A report from the National Asthma Education and Prevention Program coordinating committee expert panel working groupJournal of Allergy and Clinical Immunology. 2020;146(6):1217-1270. doi:10.1016/j.jaci.2020.10.003

  10. Cystic Fibrosis Foundation. Five feet apart.

  11. National Organization of Rare Diseases. Cystic fibrosis.

By Kristin Hayes, RN
Kristin Hayes, RN, is a registered nurse specializing in ear, nose, and throat disorders for both adults and children.