What Are the Side Effects of Singulair?

Singulair is a medication used to treat symptoms of asthma and allergy. The effects are not immediate. Children and adults can use Singulair, and it is only available by prescription. The medication blocks the release of a chemical called leukotriene that causes runny nose, wheezing, sniffles and other allergy and asthma symptoms. Unfortunately, the same symptoms that Singulair treats can also become unwanted side effects.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Most Common Side Effect

Some Singulair side effects are more common than others. Headache was the most frequently reported side effect experienced by adults in clinical trials, according to MedTV 1. Researchers compare side effects when testing drugs by providing one group with medications and the other with placebo. Headache was reported in 18.4 percent of individuals given the medication.

Less Frequent Side Effects

A small number of patients (4.2 percent) complained of flu-like symptoms when given Singulair, according to MedTV 1. Abdominal pain occurred 2.9 percent of the time, and cough in 2.7 percent of individuals. Heartburn is also listed as a side effect of the medication.

Other Side Effects

All of these were reported in adults. Tonsillitis has been reported as a side effect of Singulair in children, as has chickenpox, sinus infection and pink eye.


Serious side effects can occur with Singulair and should be immediately reported to your physician. Symptoms that seem worse related to asthma and allergy when taking Singulair require immediate attention. Many medications can affect the liver. Signs of liver damage include:

  • yellow eyes
  • skin
  • abdominal pain
  • bruising
  • nausea
  • fatigue
  • dark or orange-looking urine

Tell you doctor about other medications you are taking. Singulair can interact with some anticonvulsant medications and sedatives. Your physician will decide whether you are at risk for side effects or drug interactions from Singulair.


The best way to know if you are having a side effect from taking Singulair is to discuss your concerns with your doctor. Even if a side effect is not listed, it is important to remember that not feeling well can be a sign that something else is wrong. Never dismiss your symptoms as something you should learn to live with. The most alarming side effect of Singulair is allergic reaction, which includes rash, swelling, itching, hives, shortness of breath and wheezing.include:

  • The most alarming side effect of Singulair is allergic reaction
  • which includes rash
  • swelling
  • itching
  • hives
  • shortness of breath
  • wheezing