Singulair Side Effects: What are They and How to Manage Them?

If it seems like nearly everyone you know suffers from asthma symptoms, allergic reactions, or both, it’s because they probably do.

Asthma affects an estimated 25 million Americans, i.e. one in every 13 people, and has been on the rise since the 1980s across all ages, races, and genders. Meanwhile, more than 50 million Americans experience various types of allergies each year, making allergies the sixth leading cause of chronic illness in the United States.

Allergies are the most common health issue affecting children in the United States, while asthma is the leading chronic health condition in children.

Medications like Singulair (brand name for montelukast) are intended to treat both conditions, but Singulair side effects have gotten some negative attention in the press recently.

What exactly are the Singulair side effects, and how can you manage them?

What is Singulair?

Singulair, sold under the generic name montelukast, is a medication belonging to a class of drugs called leukotriene inhibitors.

Leukotrienes are chemicals that are released by the body when it detects an allergen in your airways, like dust or pollen. Leukotrienes are responsible for the swelling in the lungs and the tightening of the airways that occur during an asthma attack which make it difficult to breathe.

The medication was first approved by the U.S. Food and Drug Administration (FDA) in 1998 for the treatment of asthma symptoms. Singulair comes in the form of both a tablet and a chewable tablet.

What is Singulair used to treat?

Singulair is approved for the prevention of asthma attacks in adults and children as young as 12 months old, the prevention of exercise-induced bronchoconstriction (a narrowing of the air passages in the lungs that is caused by exercise) in children as young as 6 years old and adults, and the treatment of year-round allergy symptoms in children and adults as young as 6 months old.

Singulair can also be used in the treatment of seasonal allergies in children at least 2 years old and adults.


Asthma is a chronic breathing problem disease that causes the airways to narrow and become inflamed during an asthma attack.

During an attack, excess mucus production occurs, which when combined with the other symptoms of the condition, makes it difficult to breathe.

While some people have mild forms of asthma, others have serious, potentially life-threatening forms of the disease; it is important to note that the severity of the condition can change over time. 

Asthma is triggered by things like extreme weather changes, chemicals, dust mites, exercise, pollen, smoke, and stress, and each person’s triggers are different.

The best way to prevent an asthma attack is to learn your triggers and avoid them, but some people need to take asthma medications like Singulair in order to manage their condition.

Symptoms of an asthma attack include shortness of breath, wheezing, coughing, and chest tightness, and it can cause a medical emergency where an inhaler isn’t enough to reopen the airways. 

Allergic rhinitis 

Allergic rhinitis, or hay fever, is a group of symptoms affecting the sinuses and nose.

Allergic rhinitis develops when a person’s body becomes overly sensitive to something in the environment, known as an allergen.

Although most people do not experience allergic reactions to the allergen, the immune system of a person with allergies begins to attack the invader, causing an allergy attack.

During an allergy attack, the body releases inflammatory mediators like histamines, which bind to receptors on other cells in the body.

Allergy symptoms are experienced once the histamines bind to the receptors, causing flu-like symptoms such as runny nose, itchy nose or throat, nasal congestion, sneezing, itchy/watery eyes, sinus pain, and sinus pressure.

Allergic rhinitis can be triggered by outdoor allergens, such as pollen from grass, flowers, trees, or weeds, as well as indoor allergens, like dust mites, pet hair or dander, and mold, or other irritants, including perfume, smoke, and vehicle exhaust.

People suffering from allergic rhinitis may have symptoms throughout the year (perennially) or only during certain seasons.

Seasonal allergic rhinitis is most often caused by sensitivity to airborne mold spores or different types of pollen, while perennial allergic rhinitis is most often caused by pet hair or dander, dust mites, cockroaches, or mold.

People can experience both perennial and seasonal allergic rhinitis, depending on the allergens that irritate them.

What are the side effects of Singulair?

The most common side effects associated with Singulair are mild and do not require medical attention. Side effects commonly associated with Singulair include:

  • Upper respiratory infection
  • Heartburn
  • Headache
  • Cough
  • Diarrhea
  • Flu
  • Sinus infection
  • Fever
  • Sore throat
  • Stomach pain
  • Earache and ear infection
  • Runny nose
  • Skin rash
  • Bruising
  • Tiredness
  • Sleepwalking

Patients are most likely to experience these side effects when they first begin using Singulair; side effects generally decrease over time.

One of the rare but serious side effects of Singulair is an increase in certain white blood cells, called eosinophils, and the possibility of inflamed blood vessels throughout the body, a condition called systemic vasculitis.

This side effect sometimes occurs in people with asthma who use Singulair, or people who take an oral steroid medication that is being stopped or decreased in dosage.

Another set of possible side effects pertaining to mental health has also been highlighted in recent months. In March of 2020, the FDA announced that it would be requiring a boxed warning – the agency’s most prominent warning – in the prescribing information for Singulair (montelukast) due to a risk of neuropsychiatric events associated with the medication.

The boxed warning for Singulair is predominantly due to a link between suicide and suicidal thoughts and Singulair. Other neuropsychiatric events associated with Singulair include agitation, sleeping problems, and depression.

Singulair generally does not have drug interactions, and you should continue to take any prescription drugs you’re already on unless otherwise advised by a health care professional. 

It’s not currently indicated that the amounts of Singulair that pass into breast milk are substantial enough to affect infants. 

How can the side effects of Singulair be managed?

Due to the FDA’s boxed warning for Singulair, the medication is no longer recommended for the treatment of mild asthma and allergic rhinitis symptoms.

Instead, the FDA recommends that patients try other medications like an over-the-counter antihistamine to control mild symptoms. Patients who must take Singulair in order to manage their symptoms should receive medical advice and counseling by their physician regarding potential mental health side effects before beginning their treatment regimen, especially if other medical conditions are present.

Patients should immediately stop using the medication if they notice any serious side effects and mental health changes, including severe mood changes, anxiousness, aggressive behavior, disorientation, or suicidal thoughts.

It is recommended that patients check in regularly with a healthcare provider while taking Singulair, especially to report side effects that are new or worsening.  

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