Medication

Montelukast (Singulair)

Montelukast is an asthma and allergy tablet sold as Singulair. In dermatology it is occasionally added for chronic hives that antihistamines have not controlled. It carries an FDA boxed warning for serious neuropsychiatric events, and it is not a first choice.

At a Glance

Montelukast (Singulair) is a leukotriene receptor blocker approved for asthma, exercise-induced breathing problems, and allergic rhinitis. Its use in hives is off-label: it is sometimes added on top of an antihistamine when standard treatment has not worked. The evidence for that is limited and mixed. Montelukast also carries a boxed warning — the FDA's strongest — for serious neuropsychiatric events including agitation, aggression, depression, sleep disturbance, and suicidal thoughts and behavior. That warning is the reason it is an add-on considered late, not an early option.

Key Facts

AKA	Singulair (generic: montelukast sodium)
Drug Class	Leukotriene receptor antagonist
Rx or OTC	Prescription only
Typical Strength	10 mg once daily for adults; chewable 4 mg and 5 mg for children
Time to Work	If it is going to help hives, usually within two to four weeks
Evidence Level	Approved and effective for asthma and allergic rhinitis. Limited and inconsistent evidence for chronic hives, as an add-on
Important	FDA boxed warning for serious neuropsychiatric events, including suicidal thoughts and behavior. Stop it and contact a healthcare provider if behavior or mood changes.

How It Works

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Histamine is not the only chemical mast cells release. They also release leukotrienes, a separate family of inflammatory messengers that widen blood vessels, make them leak, and pull inflammatory cells into tissue. In the lungs they tighten airways; in the skin they contribute to swelling and wheals.

Antihistamines block histamine. They do nothing to leukotrienes. Montelukast blocks the receptor that one of those leukotrienes acts on, so it covers a pathway that an antihistamine leaves open.

That is why it makes theoretical sense as an add-on for hives that antihistamines have not fully controlled. In practice, the results have been inconsistent. Studies have been small and mixed, and international urticaria guidelines describe it as an option with low-quality evidence rather than a reliable step. Some clinicians report it is more useful in hives triggered or worsened by aspirin and other anti-inflammatory painkillers, where leukotrienes play a bigger role, though this too is not firmly established.

What It Treats

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Hives (Urticaria)

Limited evidence

Montelukast is a leukotriene receptor antagonist occasionally added in chronic hives. Benefit is inconsistent, and it carries a boxed warning for neuropsychiatric effects.

Who It's For & Who It's Not

Who it's for

Adults with chronic hives that are still active after a second-generation antihistamine has been tried and its dose raised under supervision, where the treating doctor judges the potential benefit worth the boxed-warning risk. It is a more natural fit for someone who also has asthma or allergic rhinitis, because then it is treating something it is actually approved for.

Who it's not for

Anyone as a first treatment for hives — it is not, and should not be, an early step. Anyone with a history of depression, anxiety, suicidal thoughts, or other significant mental health problems, unless a doctor has weighed that carefully. The FDA is explicit that for allergic rhinitis it should be reserved for people who cannot use or have not responded to other treatments. It is also not a rescue drug and does nothing for a sudden severe allergic reaction, which needs epinephrine.

How to Take It

How to take it

For adults the dose is 10 mg once daily, taken with or without food. When it is used for allergy or hives it is often taken in the evening. Because use for hives is off-label, the dose, timing, and duration should come from the doctor treating you.

What to watch for while taking it

This is the part that matters more than the dosing. The FDA boxed warning directs patients and caregivers to be alert for changes in behavior or new neuropsychiatric symptoms, and to stop the drug and contact a healthcare provider immediately if they appear. Tell the people around you that you are starting it and what to look for — mood change is often more obvious to a partner or parent than to the person taking it. This applies to children as much as adults.

Where it sits in the plan for hives

It is an add-on, not a foundation. The order isa second-generation antihistamine such as cetirizine, levocetirizine, or fexofenadine; then raising that antihistamine's dose above the standard amount under medical supervision, which is what dermatologists commonly do and what most often works; then add-ons such as famotidine or montelukast; then Xolair (omalizumab), which has far better evidence for antihistamine-resistant chronic hives. Repeated or long courses of prednisone are not an acceptable long-term answer.

What to Avoid

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Phenobarbital and some other drugs that speed up liver metabolism can reduce montelukast levels; tell your prescriber everything you take.

Ignoring mood or behavior changes

Agitation, aggression, unusual dreams or nightmares, insomnia, low mood, anxiety, irritability, or any thought of self-harm should prompt stopping the drug and contacting a healthcare provider straight away. Do not wait to see if it passes.

Treating it as an as-needed drug

It is taken daily. It will not stop a flare that has already started, and it is not a rescue medicine for an asthma attack either.

Assuming it is a mild drug because it is common

It is very widely prescribed, which is not the same as harmless. The boxed warning was added because reports of serious neuropsychiatric events kept accumulating.

Alcohol

There is no specific interaction, but alcohol can worsen mood changes, which is the side effect that matters most here.

Side Effects

Common and expected

Headache.
Abdominal pain or upset stomach.
Sore throat and upper respiratory symptoms.
Tiredness.
Vivid dreams or disturbed sleep. This sits on the boundary between a common nuisance and the neuropsychiatric effects below, and it should be reported rather than tolerated.

Tell your doctor

Any change in mood, behavior, sleep, or concentration — in yourself or in a child taking it. Report it rather than waiting for the next appointment.
Bedwetting, unusual irritability, or behavior change in a child.
No improvement in your hives after about four weeks, which is a reason to stop rather than continue.

Stop and get care

Serious neuropsychiatric events. The FDA boxed warning names agitation, aggression, depression, sleep disturbances, and suicidal thoughts and behavior, including suicide. If any of these occur, stop montelukast and contact a healthcare provider immediately. If someone is at immediate risk of harming themselves, call emergency services or a suicide crisis line right away.
Signs of a serious allergic reaction to the drug: swelling of the face, lips, or tongue, trouble breathing, or a rapidly spreading rash.
A new rash with fever, numbness or tingling, worsening breathing, or sinus symptoms alongside blood test changes — a rare inflammatory condition affecting blood vessels has been reported in people taking montelukast, usually those with asthma reducing their steroids.

Monitoring

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No routine blood tests are needed. The monitoring that matters here is behavioral: you and the people close to you should be actively watching for changes in mood, sleep, or behavior, and the prescriber should ask about this at every review. That is a direct requirement of the boxed warning, not an optional extra.

How Long Until It Works

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For asthma and allergic rhinitis, benefit usually appears within the first day or two and settles over a couple of weeks.

For hives, it is slower and less predictable. If it is going to add anything on top of your antihistamine, you would generally expect to see it within two to four weeks. If four weeks pass with no change, the sensible conclusion is that it is not working for you, and continuing a drug carrying a boxed warning without benefit is not a good trade.

What Happens When You Stop

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Montelukast can be stopped without tapering. If it was helping your hives, they may drift back over days to weeks; your antihistamine should stay in place while you find out.

If you are stopping because of mood or behavior changes, those usually improve after the drug is discontinued — but report them to a healthcare provider rather than simply stopping and saying nothing. It matters for your record, and it matters for anyone considering prescribing it to you again.

If you are taking montelukast for asthma as well as hives, do not stop it on your own. Stopping asthma treatment without a plan can lead to a flare, so that has to be arranged with your prescriber.

Who should not take it+

Do not take montelukast if you have reacted to it before. It should be used with great caution, or not at all, in anyone with a history of depression, anxiety, suicidal thoughts, or other significant mental health conditions — discuss this openly before starting. The FDA advises reserving it for allergic rhinitis only in people who cannot use or have not responded to other treatments, because of the risk of neuropsychiatric events. It is not a rescue medicine for an asthma attack or a severe allergic reaction. If you are pregnant or breastfeeding, discuss it with your doctor.

FAQ+

Why does montelukast have a boxed warning?Because serious neuropsychiatric events have been reported with it. The FDA's boxed warning — the strongest warning a label can carry — lists agitation, aggression, depression, sleep disturbances, and suicidal thoughts and behavior, including suicide. It also states that because of this risk, the benefits may not outweigh the risks in some people, particularly when symptoms are mild and can be treated another way. Anyone taking it should stop and contact a healthcare provider if behavior changes or new symptoms appear.

Does montelukast work for hives?Sometimes, as an add-on, and the evidence is limited. It is not approved for hives and guidelines describe the supporting studies as low quality. It is worth a defined trial in chronic hives that antihistamines have not controlled, with a clear plan to stop it if nothing changes in about four weeks.

Should I try it before increasing my antihistamine?Generally no. For chronic hives, the guideline step after a standard antihistamine dose fails is to raise that antihistamine's dose under medical supervision — that is more effective than montelukast and does not carry a boxed warning. Montelukast comes later.

Can children take it for hives?It is approved for asthma and allergic rhinitis in children, but the boxed warning applies fully to them, and behavior changes, nightmares, irritability, and bedwetting are reported. Off-label use for hives in a child needs a clear reason and close watching by the family.

Is it a steroid?No. It works on leukotrienes, a different inflammatory pathway, and it does not have the side effects of prednisone or topical steroids.

What should I watch for when I start it?Changes in mood, sleep, dreams, concentration, irritability, or behavior. Tell someone close to you that you have started it and ask them to say something if you seem different — mood change is often more visible from outside.

What are the alternatives for stubborn hives?Raising the second-generation antihistamine dose under supervision first, then add-ons such as famotidine, then Xolair (omalizumab), which has strong evidence for chronic hives that resist antihistamines. Long-term prednisone is not a solution.

Will it help my eczema?There is no good evidence that it does. Eczema needs anti-inflammatory treatment on the skin, or a targeted drug like Dupixent when it is severe.

Can I stop it suddenly?For hives, yes — no taper is needed. If you also take it for asthma, do not stop without speaking to your prescriber, because your asthma control could slip.