How does Flonase work to help relieve allergies?

Mike Bohl, MD, MPH, ALM - Contributor Avatar

Written by Michael Martin 

Mike Bohl, MD, MPH, ALM - Contributor Avatar

Written by Michael Martin 

last updated: Jul 12, 2021

3 min read

Whether you’ve seen an ad for Flonase or know someone who swears by it, you may be familiar with this steroid nasal spray. But how does Flonase work to improve allergy symptoms? Read on to learn more about this popular allergy medication. 


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What is Flonase?

Fluticasone (active ingredient fluticasone propionate) is a corticosteroid nasal spray. It’s FDA-approved to treat allergic rhinitis (like seasonal allergies), nonallergic rhinitis, and nasal polyps. It also comes in an oral inhaled form to help people with asthma breathe easier. 

When it comes to nasal allergy symptoms, like runny nose, congestion, etc., Flonase nasal spray is an effective treatment. Studies suggest that steroid nasal sprays are better at improving allergy symptoms and provide more complete allergy relief than allergy pills, like loratadine (brand name Claritin), fexofenadine (brand name Allegra), and cetirizine (brand name Zyrtec). Another example of a steroid nasal spray is triamcinolone acetonide (brand name Nasacort) (Akhouri, 2021).

Flonase is FDA-approved for use in children over two years of age. 

Although the signs and symptoms of a common cold can resemble those of allergies, don't use Flonase to treat your common cold—it won’t work for that (Hayward, 2015).

How does Flonase work?

Fluticasone and other nasal glucocorticoids are anti-inflammatory medications, meaning they reduce inflammation. They do this by switching off multiple pathways in the body that produce inflammatory substances. These inflammatory substances include tryptases, prostaglandins, leukotrienes, chemokines, and others. Corticosteroids (like Flonase) decrease the activation of inflammatory cells, reduce tissue swelling, and constrict blood vessels (vasoconstriction)—but the precise mechanisms are unknown. These anti-inflammatory effects lead to an overall improvement in allergy symptoms (Remien, 2021). 

Flonase is used to treat allergic rhinitis caused by airborne allergens, like pollens, molds, dust mites, or pet dander. It’s highly effective at relieving allergy symptoms like nasal congestion, watery eyes, an itchy nose, and sneezing from hay fever because it delivers the medication directly to the nasal cavity. 

Flonase is designed to provide symptom relief daily. Some people may start seeing symptom relief within 12 hours of starting Flonase for the first time, but it can take several days to build up to full effectiveness in the body (UpToDate, n.d.). 

Flonase dosage

Fluticasone propionate nasal sprays are available both by prescription and over-the-counter (OTC) to relieve your allergy symptoms. Several OTC forms of Flonase are available: Flonase Sensimist Allergy Relief, Flonase Allergy Relief, Children’s Flonase Sensimist Allergy, and Children’s Flonase Allergy Relief. Each spray has 27.5 mcg of medication (UpToDate, n.d.). 

Xhance is the brand name of another medication containing fluticasone propionate, but it is mainly used for nasal polyps and has 93 mcg of the active ingredient per spray (UpToDate, n.d.). 

The typical dose of Flonase is one or two sprays in each nostril 1–2 times a day, and it usually provides 24-hour relief.

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Flonase side effects

The most common side effects associated with Flonase allergy medicine are headaches, nasal irritation, and nosebleeds. Other side effects include nausea, vomiting, sore throat, trouble breathing, and cough. Some rare side effects include nasal problems like nose sores or nose ulcers and a fungal infection in the nose, mouth, or throat called thrush (UpToDate, n.d.). 

If misused, Flonase can also cause a hole to form in the cartilage of the nose (called nasal septal perforation). Since fluticasone is a steroid, it carries a small risk of worsening glaucoma and/or cataracts in some people. Like all drugs, there is always the chance of serious allergic reactions (UpToDate, n.d.). 

Flonase can also cause a weakened immune system (immunosuppression) or increased risk of getting infections, as well as lowered steroid hormone levels (also known as adrenal insufficiency) (UpToDate, n.d.). 

Flonase interactions

Since Flonase is broken down by enzymes in the liver, like cytochrome P450, any drug that blocks the enzyme’s actions may raise Flonase levels in your blood—this increases your risk of side effects. For example, people taking HIV medications like ritonavir should check with their healthcare provider before starting Flonase (FDA, 2019).  

Tell your healthcare provider about any over-the-counter or prescription medications you may be taking to learn about potential drug interactions. 

Flonase warnings

People with certain medical conditions should seek medical advice from a healthcare professional before starting Flonase, as they may be at an increased risk of side effects. 

If you have liver problems, cataracts, glaucoma, tuberculosis, or other bacterial, fungal, or viral infections (like chickenpox), you may want to check with your provider before using Flonase (UpToDate, n.d.). 

There is not enough data to know if this is safe to take while pregnant or breastfeeding—talk to your healthcare provider about the risks and benefits of taking Flonase.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

July 12, 2021

Written by

Michael Martin

Fact checked by

Mike Bohl, MD, MPH, ALM

About the medical reviewer

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.