Yes, you can take montelukast and cetirizine at the same time. The two medications work through completely different pathways, and clinical trials have specifically studied them in combination without finding harmful interactions. In fact, doctors often prescribe them together for allergic rhinitis because the pairing can control symptoms better than either drug alone.
Why the Combination Works
Allergic reactions trigger two major inflammatory chemicals in your body: histamine and leukotrienes. Cetirizine blocks histamine, which is responsible for sneezing, runny nose, and itchy eyes. Montelukast blocks leukotrienes, which primarily cause nasal congestion and swelling in your airways. Because each drug handles a different piece of the allergic response, taking both covers more ground than either one can on its own.
A systematic review and network meta-analysis of combination therapies found that pairing montelukast with an antihistamine like levocetirizine (a close relative of cetirizine) significantly improved daytime nasal symptoms, nasal congestion, sneezing, nasal itching, and nasal discharge compared to montelukast alone. The combination also improved quality-of-life scores for allergy sufferers. Separate research found the montelukast-cetirizine combination was as effective as prescription nasal steroid sprays like mometasone and budesonide for seasonal allergies.
How to Time Each Dose
Cetirizine is typically taken once daily, morning or evening. Montelukast is also once daily. If you’re taking montelukast for asthma, it should be taken in the evening. For seasonal allergies alone, montelukast can be taken morning or evening, as long as you pick a consistent time each day. Both can be taken with or without food, and there’s no issue swallowing them at the same moment.
Many people find it simplest to take both in the evening before bed. This has the added benefit of letting cetirizine’s mild sedative effect work in your favor overnight rather than during the day.
Side Effects to Watch For
Cetirizine’s most discussed side effect is drowsiness. A meta-analysis of clinical trials found that the drowsiness rate with cetirizine 10 mg was roughly 6.5 percentage points higher than placebo in some study designs, though in more tightly controlled trials the difference nearly disappeared. Still, some people do notice fatigue, especially in the first few days.
Montelukast carries a more serious concern. The FDA added its strongest warning (a boxed warning) to montelukast in 2020, flagging the risk of neuropsychiatric side effects. These can include agitation, irritability, vivid or bad dreams, trouble sleeping, depression, anxiety, confusion, and in rare cases suicidal thoughts. A pediatric study of the montelukast-levocetirizine combination found that about 22% of children developed at least one neuropsychiatric symptom during treatment, with irritable behavior (13%) and nightmares (7%) being the most common.
These side effects are not unique to taking the combination. They are linked to montelukast itself. But if you notice mood changes, unusual irritability, vivid nightmares, or any behavioral shifts after starting montelukast, whether alone or alongside cetirizine, that’s a signal to stop taking it and talk to your prescriber.
Who Benefits Most From This Combination
The pairing makes the most sense for people whose allergies aren’t fully controlled by an antihistamine alone, especially if nasal congestion is a major symptom. Antihistamines like cetirizine are good at stopping sneezing and itching but often fall short on stuffiness. Adding montelukast targets that congestion directly.
People who have both asthma and allergies may get particular value from this combination. Up to 78% of asthma patients also have allergic rhinitis, and montelukast is approved for both conditions. Using it alongside cetirizine can address airway and nasal symptoms simultaneously. For people with allergies alone and no asthma, the FDA’s boxed warning has shifted prescribing habits. Many doctors now reserve montelukast for cases where antihistamines and nasal sprays haven’t been enough, rather than using it as a first-line option.
How It Compares to Nasal Steroid Sprays
Nasal corticosteroid sprays remain the most broadly effective single treatment for allergic rhinitis. But the montelukast-cetirizine combination has performed comparably to nasal steroids in clinical trials. This makes it a reasonable alternative for people who dislike nasal sprays or don’t tolerate them well. Some patients with more severe allergies use all three: an antihistamine, montelukast, and a nasal steroid spray together.