What Xolair Side Effects Should I Be Concerned With?

Xolair (omalizumab) is an injectable prescription medication that is primarily used to treat moderate to severe asthma, a long-term lung condition that makes it difficult to breathe. While this medication is generally well tolerated, there are side effects that you should be aware of.

Your healthcare provider may recommend Xolair if you have asthma or another allergy-related condition that has not responded well to other treatments. This medication helps prevent an allergic response by blocking the effect of a certain protein in the body that causes allergy symptoms.

Older woman in doctor's office speaking with doctor.
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This article explains the common and rare side effects associated with Xolair. It also covers the safety of long-term use, as well as what to discuss with your healthcare provider before trying this medication.

What Are the Side Effects of Xolair?

In a clinical study of over 2,000 adults, the most common side effects experienced—and the percentage of people who experienced them—were as follows:

  • Injection site reactions like arm swelling or tenderness (45%)
  • Colds (23%)
  • Sinus infection, or inflammation around the nasal airways (16%)
  • Headache (15%)
  • Sore throat (11%)

Keep in mind, though, that individuals receiving a fake treatment in this clinical study showed a similar amount of these reactions.

Some individuals may also experience side effects such as stomachaches, nose bleeds, ear pain, and joint pain.

A severe allergic reaction known as anaphylaxis is possible, though rare. This reaction can cause hives, difficulty breathing, itching, as well as throat and tongue swelling.

Certain types of cancer are also thought to be associated with Xolair treatment. However, in long-term studies, it did not increase the risk of cancer or the risk of cancer returning.

If you are experiencing any side effects, be sure to let your healthcare provider know right away. If you believe you are having a severe allergic reaction, call 911. If available, use an epinephrine autoinjector to administer epinephrine and stop the reaction.

Is Xolair Safe Long Term?

The Food and Drug Administration (FDA) issued a statement in 2014 noting a slightly higher potential risk of heart- and blood vessel-related issues in those taking Xolair.

In a nine-year study:

  • The risk of having a severe allergic reaction was very low.
  • The medication was generally well tolerated.
  • No heart issues were reported.
  • No issues related to the blood vessels of the brain were reported.
  • This medication showed potential to interfere with the body's ability to clot, or stop bleeding.
  • This medication was not associated with an increased risk of getting cancer or having cancer come back.
  • Long-term use was not associated with an increased risk of experiencing side effects.

What Should I Talk About With My Healthcare Provider?

Before starting a Xolair treatment program, you may want to speak with your healthcare provider about:

  • The purpose of you being on Xolair
  • Whether there are other treatment options you can consider alongside Xolair
  • The potential that Xolair may not help with your condition
  • Expected and possible outcomes of treatment
  • Risks of treatment including anaphylaxis and the other potential side effects
  • Proper use of an epinephrine autoinjector, which stops the allergic reaction associated with anaphylaxis
  • Problems that may develop if you do not follow treatment regimen or instructions correctly
  • The need for regular follow-up and monitoring of symptoms
  • If you need to notify your healthcare provider of any unscheduled office or emergency room visits related to your condition


Xolair is a prescription medication that is mainly used to treat moderate to severe asthma.

Side effects can range from mild to severe. Rare and more serious side effects may include anaphylaxis, as well as an increased risk of experiencing heart or blood vessel related issues.

Research suggests that long-term use of Xolair is considered safe and not associated with an increased risk of getting cancer or experiencing side effects.

Frequently Asked Questions

  • Does Xolair have a black box warning?

    Xolair has a boxed warning for anaphylaxis.

  • How long do the side effects of Xolair last?

    Side effects may show up shortly after the Xolair injection or up to five days later. How long they will last will depend on the side effect you are experiencing.

  • How long can you stay on Xolair?

    Studies indicate that long-term use of Xolair is safe for most individuals.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Johns Hopkins Medicine. Patient information letter: xolair (omalizumab).

  2. MedlinePlus. Omalizumab injection.

  3. Di Bona D, Fiorino I, Taurino M, et al. Long-term “real-life” safety of omalizumab in patients with severe uncontrolled asthma: a nine-year studyRespiratory Medicine. 2017;130:55-60. doi:10.1016/j.rmed.2017.07.013

  4. U.S. Food and Drug Administration. FDA drug safety communication: FDA approves label changes for asthma drug xolair (omalizumab), including describing slightly higher risk of heart and brain adverse events.

By Pat Bass, MD
Dr. Bass is a board-certified internist, pediatrician, and a Fellow of the American Academy of Pediatrics and the American College of Physicians.