Montelukast treats three FDA-approved conditions: asthma, allergic rhinitis (hay fever), and exercise-induced breathing difficulties. Sold under the brand name Singulair, it works by blocking inflammatory chemicals in the body called leukotrienes, which play a central role in airway tightening, swelling, and mucus production.
How Montelukast Works
When your body encounters an allergen or irritant, certain immune cells release chemicals called cysteinyl leukotrienes. These chemicals trigger a chain reaction: airways tighten, blood vessels become leaky, and inflammatory cells flood into the surrounding tissue. Over time, this cycle can reshape and permanently narrow the airways.
Montelukast blocks the receptor these chemicals latch onto, cutting off the signal before it can cause bronchoconstriction, swelling, or eosinophil buildup (a type of white blood cell that drives allergic inflammation). It does not work like an inhaler that relaxes muscles directly. Instead, it prevents the inflammatory cascade upstream.
Asthma
Montelukast is approved for long-term asthma management in patients as young as 12 months. It is taken once daily in the evening, and clinical trials show the effect kicks in after the very first dose, with protection lasting a full 24 hours. It is not a rescue medication. You still need a fast-acting inhaler for sudden symptoms.
Compared to inhaled corticosteroids, the standard first-line controller for asthma, montelukast performs similarly on most real-world measures: frequency of asthma attacks, flare-ups, and need for rescue medication. In one head-to-head trial, the percentage of days with controlled asthma was nearly identical between montelukast and an inhaled steroid, with a 98% overlap in the distribution of results. Inhaled corticosteroids do produce better lung function numbers on breathing tests, but researchers have noted that this improvement in airflow may overstate the actual clinical difference between the two treatments. In practice, many patients respond equally well to either option.
Montelukast is most often used as an alternative for people who cannot tolerate or prefer not to use inhaled steroids, or as an add-on therapy when an inhaler alone is not enough.
Allergic Rhinitis
Montelukast is also approved for seasonal allergic rhinitis in patients 2 years and older and for year-round (perennial) allergic rhinitis in patients 6 months and older. It helps with nasal congestion, sneezing, and runny nose by reducing the same leukotriene-driven inflammation that occurs in the nasal passages.
That said, current clinical guidelines do not recommend montelukast as a first choice for allergic rhinitis. Antihistamines and nasal corticosteroid sprays are more effective for most people. Montelukast is typically reserved for patients who do not respond well to those options or who also have asthma, since one pill can address both conditions simultaneously.
Exercise-Induced Breathing Difficulty
For people whose airways tighten during or after physical activity, montelukast is approved as a preventive treatment in patients 6 years and older. Clinical trials showed significant protection when it was taken 2 hours before exercise, and some patients remained protected for up to 24 hours after a single dose. This makes it a convenient option for athletes or active individuals who experience chest tightness, coughing, or wheezing with exertion, since it does not need to be timed precisely before every workout the way a pre-exercise inhaler does.
Off-Label Uses
Doctors sometimes prescribe montelukast for conditions beyond its three approved uses. One of the more studied off-label applications is chronic hives (urticaria), particularly when swelling is the dominant symptom. In patients with this type of chronic hives, adding montelukast to a daily antihistamine improved symptoms in a significant number of people and led to complete resolution in roughly two-thirds of patients. It has also been tried for conditions like nasal polyps and COPD, though evidence for those uses is less robust.
Dosing by Age
Montelukast comes in three forms, matched to age:
- Adults and teens 15+: one 10-mg film-coated tablet, taken once daily in the evening.
- Children 6 to 14: one 5-mg chewable tablet.
- Children 2 to 5: one 4-mg chewable tablet or one packet of 4-mg oral granules.
- Infants 6 to 23 months: one packet of 4-mg oral granules.
The oral granules for young children can be placed directly in the mouth, dissolved in a teaspoon of room-temperature formula or breast milk, or mixed into a small amount of soft food. The FDA specifies only applesauce, carrots, rice, or ice cream based on stability testing. Once the packet is opened, the full dose needs to be given within 15 minutes.
Mental Health Side Effects
In March 2020, the FDA added its strongest safety warning, a boxed warning, to montelukast’s label. The warning addresses serious mood and behavior changes that have been reported in some patients, including agitation, depression, sleep disturbances, and suicidal thoughts. Completed suicides have been reported. These effects can occur at any age.
Because of this risk, the FDA also tightened its guidance on prescribing montelukast for allergic rhinitis specifically, advising that it should be reserved for patients who have not responded adequately to other allergy treatments. For asthma and exercise-induced breathing problems, where fewer alternatives exist, the benefits may still outweigh the risks for many patients. If you or your child are taking montelukast, pay attention to any new or worsening changes in mood, behavior, or sleep, and report them promptly.