Montelukast Side Effects: What You Need to Know Before Taking It

When you take montelukast, a leukotriene receptor antagonist used to prevent asthma and allergy symptoms. Also known as Singulair, it helps control inflammation in the airways by blocking substances called leukotrienes that trigger swelling and mucus production. Many people use it daily without issues, but it’s not just another pill—there are real, documented side effects you should be aware of, especially if you’ve noticed changes in your mood, sleep, or behavior since starting it.

The most common side effects of montelukast are mild: headache, stomach pain, sore throat, or a stuffy nose. These usually fade after a few days. But there’s another layer—something the FDA has flagged since 2008 and strengthened in 2020. montelukast can cause serious neuropsychiatric side effects, including depression, anxiety, aggression, nightmares, and even suicidal thoughts. These aren’t rare outliers. They’re reported consistently across clinical data and patient forums. If you or someone you care for starts feeling "off" emotionally after beginning montelukast, don’t wait. Talk to your doctor. It’s not always the medication’s fault, but it’s one of the few drugs where mental health changes are listed as a known risk—not just a footnote.

Some people wonder if montelukast is safer than steroids. It doesn’t cause weight gain or bone thinning like inhaled corticosteroids, but it brings its own set of trade-offs. If you’re using it for allergies, not asthma, the benefit might be smaller, and the risk of side effects still exists. It’s also not meant for sudden asthma attacks—you still need your rescue inhaler. And if you’re on other meds, like aspirin or NSAIDs, montelukast doesn’t interact badly, but it doesn’t fix everything either. The key is knowing what it does and doesn’t do.

What you’ll find below are real patient experiences and clinical breakdowns of montelukast side effects, how they compare to other asthma and allergy drugs, and what to do if you suspect something’s wrong. We’ve pulled insights from posts that dig into mental health risks, long-term use, and how to spot warning signs before they escalate. This isn’t theoretical. These are the stories people wish they’d read before starting the pill.