If you have asthma, hives, or nasal polyps, your doctor might suggest Xolair (omalizumab) as a treatment option for your condition.

Xolair is a prescription medication that’s used to treat:

  • asthma in adults and in children ages 6 years and older
  • nasal polyps in adults
  • chronic (long-lasting) hives from an unknown cause in adults and in children ages 12 years and older

Xolair comes as a liquid solution or as a powder that’s mixed with liquid to form a solution. Xolair is given as an injection under your skin. You’ll receive Xolair injections at your doctor’s office.

Xolair belongs to a group of medications called biologics. These drugs are made from living cells.

If Xolair works to treat your symptoms, you’ll likely use it long term. For more information about Xolair, including details about its uses, see this in-depth article.

Like other drugs, Xolair can cause mild or serious side effects. Keep reading to learn more.

Below are a few of the more common side effects reported by people who took Xolair in studies. These side effects can vary depending on which condition you’re receiving the drug to treat.

More common side effects in people receiving Xolair for asthma include:

  • pain, including joint pain and pain in your legs
  • fatigue (low energy)*
  • dizziness
  • itching
  • skin rash

More common side effects in people receiving Xolair for nasal polyps include:

  • headache*
  • injection-related side effects*
  • joint pain*
  • abdominal (belly) pain
  • dizziness

More common side effects in people receiving Xolair for hives include:

* To learn more about this side effect, see the “Side effects explained” section below.

Some people may experience mild side effects during Xolair treatment. These side effects may vary depending on the condition you’re receiving Xolair to treat.

Examples of mild side effects that have been reported in people receiving Xolair include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. Some may be easily managed, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. You shouldn’t stop Xolair treatment unless your doctor recommends it.

Xolair may cause mild side effects other than the ones listed above. See the Xolair prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Xolair, visit MedWatch.

Xolair may cause serious side effects in some people. Serious side effects that have been reported with Xolair include:

If you develop serious side effects during Xolair treatment, call your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, call 911 or your local emergency number immediately.

* Xolair has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effects explained” section below.

Common side effects have been reported in children receiving Xolair for asthma treatment, including:

If you have questions about side effects that your child may experience while being treated with Xolair, talk with their doctor.

Learn more about some of the side effects Xolair may cause.

Injection-related side effects

During treatment with Xolair, some people may experience injection-related side effects (also called injection site reactions). These are reactions that can occur where your dose of Xolair is injected. Injection-related side effects were common in clinical studies of Xolair.

Examples of injection-related side effects may include:

  • bruising
  • redness or discoloration
  • burning, stinging, or warmth in the skin
  • itching
  • rash or hives
  • pain
  • swelling

What might help

Injection-related side effects usually happen within 1 hour of your injection and last for fewer than 8 days. In most cases, people who experienced these side effects were less likely to have them after receiving the medication for a longer period of time. So your risk of this side effect may be reduced over time.

If you experience injection-related side effects during treatment with Xolair, talk with your doctor or pharmacist. They may be able to recommend ways to ease these side effects.

Hair loss

Hair loss can occur with Xolair. In studies, this was a rare side effect reported by people receiving Xolair. Hair loss only occurred in people receiving Xolair for hives.

What might help

If you experience bothersome hair loss during Xolair treatment, talk with your doctor. They may be able to recommend ways to decrease this side effect. They may also be able to recommend treatment options for hair loss.

Fatigue

You may experience fatigue (low energy) during Xolair treatment. This was a common side effect reported by people receiving Xolair for asthma in studies. But fatigue was not common in people receiving Xolair for hives or nasal polyps.

What might help

If you notice a decrease in your energy levels while receiving Xolair, talk with your doctor or pharmacist. They may be able to help determine what’s causing your fatigue and the best way to treat it.

Headache

You may experience headaches when taking Xolair. In studies, this was one of the most common side effects reported in people receiving Xolair for nasal polyps or hives. Headaches also commonly occurred in children taking Xolair for asthma.

What might help

If you experience headaches that are frequent or bothersome to you, talk with your doctor or pharmacist. They may recommend over-the-counter (OTC) treatment options, such as Tylenol (acetaminophen), or they may suggest other ways to treat your headaches.

Joint pain

Some people may develop joint pain during treatment with Xolair. Joint pain was a common side effect reported by people taking Xolair in studies.

What might help

If you develop joint pain, talk with your doctor. In some cases, joint pain can be a symptom of a more serious condition called serum sickness. This condition usually causes fever and rash along with joint pain. If you develop serum sickness, your doctor will recommend that you stop taking Xolair. They can then discuss other treatment options for your condition.

If your joint pain is not associated with serum sickness, your doctor may recommend OTC pain relievers, such as Tylenol. Or they may suggest other ways to decrease your joint pain.

Allergic reaction, including anaphylaxis

Like most drugs, Xolair can cause an allergic reaction in some people. In fact, Xolair has a boxed warning* for the risk of anaphylaxis, which is a severe allergic reaction that can be life threatening.

When you receive your first dose of Xolair, your doctor will monitor you after your injection. This is done to be sure that you don’t develop symptoms of anaphylaxis. Some people who experienced anaphylaxis had reactions after their first dose. But in some cases, anaphylaxis may not occur until a year or more after starting Xolair treatment.

It’s important to understand the symptoms of a mild and serious allergic reaction, including anaphylaxis, so you can get help right away if you develop symptoms.

Symptoms of a mild allergic reaction can include:

Symptoms of a more serious allergic reaction, including anaphylaxis, can include:

  • hives
  • constriction (tightening) of the airways in your lungs, which can cause:
    • shortness of breath
    • wheezing or a whistling sound when you inhale
    • coughing
    • pain or tightness in your chest and back
  • fainting
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

You should not use Xolair if you have ever had an allergic reaction to Xolair or any of its ingredients, including latex.

* A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest an OTC oral antihistamine, such as Benadryl (diphenhydramine), or a topical product, such as hydrocortisone cream, to manage your symptoms.

If your doctor confirms you had a mild allergic reaction to Xolair, they’ll decide if you should continue receiving it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you had a serious allergic reaction to Xolair, they may have you switch to a different treatment.

Keeping track of side effects

During your Xolair treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon after starting that dose you had the side effect
  • what your symptoms were from the side effect
  • how it affected your daily activities
  • what other medications you were also taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help your doctor learn more about how Xolair affects you. Your doctor can use this information to adjust your treatment plan if needed.

Get answers to some frequently asked questions about Xolair’s side effects.

Does Xolair cause weight gain or weight loss?

No, you shouldn’t experience weight gain or weight loss during Xolair treatment. Changes in weight were not side effects reported by people receiving Xolair in studies.

If you have unexplained weight changes during treatment with Xolair, talk with your doctor. They can help determine what may be causing your weight changes.

Is depression a side effect of Xolair?

No, Xolair should not cause depression. This was not a side effect reported by people receiving Xolair in studies. But it’s possible that living with a chronic (long-lasting) condition, such as asthma or hives, can raise your risk of depression.

If you’re feeling depressed during treatment with Xolair, be sure to talk with your doctor right away. They can determine the best way to treat your symptoms of depression.

Does Xolair cause any long-term side effects?

Yes, it’s possible that Xolair may cause long-term side effects. For example, this medication may raise your risk of heart attack, stroke, or cancer, which can all have long-term complications. But these side effects are rare.

Short-term, mild side effects are much more common with Xolair than long-term side effects. But if you’re concerned about long-term side effects with this drug, talk with your doctor or pharmacist.

How long do side effects from Xolair typically last?

It depends on which side effects you’re experiencing. For example, injection-related side effects usually go away within 8 days after your injection. These side effects are less likely to happen as your condition is treated with Xolair for a longer period of time.

Other side effects of Xolair, such as joint pain, may last longer. Some side effects may even last throughout Xolair treatment. If you’re concerned about how long a specific side effect could last, talk with your doctor or pharmacist. They may be able to recommend treatment for your side effects.

Will stopping my Xolair treatment cause any side effects?

No, you shouldn’t experience any side effects if you stop Xolair treatment. But it’s possible that stopping Xolair treatment may cause the symptoms of your condition to come back. For example, if you’re receiving Xolair to treat asthma, when you stop taking the medication, your asthma symptoms may return.

If you want to stop treatment with Xolair, talk with your doctor first. They may recommend a different medication to treat your condition.

Before you start treatment with Xolair, talk with your doctor about any other medical conditions you have or other medications you’re taking. They can determine if Xolair may be a safe treatment option for your condition.

Boxed warning: Anaphylaxis

Xolair has a boxed warning for the risk of anaphylaxis, which is a severe allergic reaction. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

If you’ve had an allergic reaction to any of the ingredients in Xolair, including latex, you should not take this medication. Symptoms of anaphylaxis may include trouble breathing, swelling of the throat or tongue, or low blood pressure.

To learn more, see the “Side effects explained” section above.

Other warnings

Xolair may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Xolair. The list below includes factors to consider.

Asthma attack or bronchospasm. If you’re experiencing trouble breathing, bronchospasm, or any other symptoms of an asthma attack, you should not use Xolair to treat it. Xolair may not be an effective medication to treat asthma attacks or bronchospasm. If you’re experiencing these symptoms, talk with your doctor about the best treatment option for your condition.

Allergic reaction. If you’ve had an allergic reaction to Xolair or any of its ingredients, including latex, your doctor likely won’t prescribe Xolair. Ask your doctor what other medications are better options for your condition.

Parasitic infection. If you have a parasitic infection (such as hookworm or roundworm), tell your doctor before you start taking Xolair. This drug may raise your risk of a parasitic infection. If you already have this type of infection, Xolair may make your condition worse. Your doctor will likely recommend treating the infection before you start receiving Xolair.

Cancer. Xolair may increase your risk of cancer. If you have cancer or have had it in the past, tell your doctor before you start Xolair treatment. Your doctor may recommend monitoring you more closely during your Xolair treatment, or they may recommend a different treatment for your condition.

Alcohol and Xolair

There are no known interactions between alcohol and Xolair. But drinking alcohol during Xolair treatment could raise your risk of certain side effects. For example, both alcohol and Xolair may cause a headache or nausea. So drinking alcohol with Xolair may make these side effects worse.

If you drink alcohol, talk with your doctor about how much (if any) may be safe for you drink during treatment with Xolair.

Pregnancy and breastfeeding while receiving Xolair

It’s not known if Xolair is safe to use during pregnancy or while breastfeeding.

If you’re pregnant or breastfeeding, or planning to become pregnant or to breastfeed, talk with your doctor before starting Xolair treatment.

You may experience side effects during treatment with Xolair. But most side effects are mild. Before starting Xolair treatment, talk with your doctor about your risk of side effects with this drug.

Questions that you may want to ask include:

  • Do I have a higher risk of side effects due to my medical conditions?
  • How should I treat side effects that I experience?
  • What should I do if I become pregnant during treatment with Xolair?

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.