10 Xolair Side Effects and How to Manage Them

If you’re living with an allergic health condition and need more help managing your symptoms, your prescriber may add a medication like Xolair (omalizumab) to your routine. You’ll receive the first few doses in their office. After that, you may be able to inject Xolair yourself at home.

Common Xolair side effects, such as headaches and fatigue, may only last a few days after your dose. Other side effects may be from an underlying condition instead, especially if they don’t improve over time. And in rare cases, severe allergic reactions to Xolair are possible. Knowing which side effects require action can help keep you safe during treatment.

Xolair side effects at a glance

Xolair is FDA approved to treat moderate-to-severe asthma, chronic rhinosinusitis with nasal polyps (CRSwNP), and chronic hives. It's also approved to lower the risk of allergic reactions to certain foods after accidental exposure. Like most medications, it can cause side effects that range from mild to severe. The likelihood of experiencing certain side effects may vary depending on your age and why you’ve been prescribed Xolair.

Common Xolair side effects can include:

• Injection site reactions

• Joint pain

• Headache

• Infections

• Stomach pain

• Dizziness

• Fatigue

• Body, arm, or leg pain

• Itching

• Nausea

• Cough

Less common and potentially serious Xolair side effects can include:

• Increased risk of parasitic infections

• Fever with joint pain, rash, and swollen lymph nodes

• Severe allergic reactions (anaphylaxis)

• Increased risk of cancer (certain types)

Keep in mind that everyone responds differently to medications. Factors that can influence side effects include your age, prescribed dose, and other medical conditions. Below, we review what you should know about 10 Xolair side effects.

1. Injection site reactions

If you’ve ever had an injection, you’ve likely experienced the redness and pain that typically follows. Injection site reactions are the most common Xolair side effect. Almost half of people in clinical studies reported bruising, stinging, or itching, among other reactions.

Injection site reactions usually happen within an hour of a Xolair injection. They’re typically mild to moderate in severity and should resolve within a few days. They also tend to happen less often with each injection.

Injection site reactions can usually be managed at home. You can try an ice pack to bring down the swelling. Over-the-counter (OTC) products, such as pain relievers and anti-itch creams, may also help for symptom relief.

Tell your prescriber if your symptoms are severe, getting worse, or not going away. Call 911 or have someone take you to the nearest ER if you develop symptoms such as shortness of breath, swelling or the face or throat, or hives.

2. Headache

Some people receiving Xolair reported headaches during clinical trials, especially those with CRSwNP or chronic hives. However, it’s important to note that headaches are common with these two conditions in general. And they happen more frequently with asthma, too.

After administering Xolair, people generally report mild headaches that resolve within a few days of their dose. But if you’re experiencing frequent or bothersome headaches with Xolair, talk to your prescriber. They can help figure out the potential cause and best next steps. 

It may also help to make sure you’re drinking enough fluids, getting adequate sleep, and minimizing potential headache triggers, such as alcohol. If needed, an OTC pain reliever may help with occasional headaches.

3. Body, joint, and leg pain

Pain involving the joints, arms, and legs is possible with Xolair. In some cases, this may also resolve within a few days after administering a dose.

But you should talk to your prescriber if you notice pain in your joints or other parts of your body that doesn’t seem to be going away. There’s a chance it may not be related to Xolair. For instance, health conditions such as asthma and chronic hives have been linked to a higher risk of arthritis in general.

Good to know: After Xolair came on the market, some people reported joint pain, along with rash, fever, and swollen lymph nodes within 5 days after an injection. If this happens to you, notify your prescriber right away. They’ll likely have you stop Xolair injections.

4. Fatigue

If you’ve been feeling low on energy, it could be due to Xolair. Similar to other side effects, this may start to subside within a few days of your dose.

During clinical trials, some adults and teens receiving Xolair for asthma reported fatigue as a side effect. Fatigue is common in people living with asthma. Sometimes, it can be a sign that your asthma isn’t being managed well enough. Keep in mind that if you’ve recently started Xolair, it can take several months to feel the full benefit.

If you’re feeling fatigued, there are a few things you can do to help boost your energy. Examples include getting enough sleep and choosing nutrient-dense foods. Talk to your prescriber if your fatigue is severe, getting worse, or not going away.

5. Dizziness

Dizziness is another possible Xolair side effect. If you’re feeling dizzy, avoid activities where dizziness could be dangerous, such as driving a car. Sit or lie down until you feel more stable on your feet.

Tell your prescriber if you’re experiencing severe dizziness, or if it’s not going away. It’s possible that there’s another cause that needs to be addressed, as dizziness has many potential culprits. But you should keep in mind that dizziness can also be a symptom of a severe allergic reaction. More on that later.

6. Itching

Xolair can help improve itching and other symptoms in people with chronic hives. But some people with asthma have reported itching from Xolair. Dermatitis, which causes itchy skin, is also a potential cause. But it’s important to note that dermatitis is also strongly linked to asthma in general.

If you notice new or worsening itching after starting Xolair, contact your prescriber. They can help you figure out whether it’s a side effect of Xolair or happening for another reason. If needed, they may recommend an anti-itch cream or other form of treatment.

7. Abdominal pain

Abdominal pain is another possible Xolair side effect, mostly in the upper part of your gut. This seems to happen more frequently in children with asthma and adults with CRSwNP. It’s not known why this side effect may occur. However, Xolair can increase the risk of parasitic infections, which may cause abdominal pain.

Tell your prescriber if you experience abdominal pain, especially if it’s not going away or if you have other symptoms, such as gas or diarrhea. They may decide to do further testing to figure out the cause.

8. Infections

During clinical trials, a number of people receiving Xolair reported higher rates of infections than those who didn’t receive it. These included upper respiratory tract infections (such as the common cold), viral infections, and sinus infections.

These types of infections are usually caused by viruses. So, you can usually manage your symptoms with OTC medications and other cold remedies at home. But if your infection is severe, getting worse, or not going away, tell your healthcare team.

If you’re already at higher risk of a parasitic infection, you may be more likely to develop one after starting Xolair. This is because Xolair works by blocking immunoglobulin E (IgE), which is an antibody that plays a role in fighting off parasitic infections. Some ways you can lower your risk of a parasitic infection with Xolair include:

• Washing your hands often

• Peeling and cooking raw fruits and vegetables

• Boiling or treating water

• Avoiding walking barefoot in areas where soil might contain parasites

If you think you might have a parasitic infection, a healthcare professional can check your stool to confirm and provide treatment.

9. Allergic reactions

Xolair has a boxed warning (the FDA’s strongest medication warning) about severe allergic reactions (anaphylaxis). However, the overall risk seems to be very low. 

A long-term study followed people injecting Xolair for asthma for up to 9 years. The results showed that out of over 10,000 injections, no immediate allergic reaction (such as anaphylaxis) occurred. Another study had 41 anaphylaxis cases out of nearly 40,000 people receiving Xolair

Allergic reactions can happen after the first Xolair dose or any doses after — even beyond a year of treatment. But most reactions seem to happen within the first few doses.

Because of this, you’ll receive your first three doses from a healthcare professional in a medical setting. That way, they’ll be able to provide treatment quickly if a reaction happens. But if no problems arise, you’ll likely be able to administer future doses at home.

If you’re injecting Xolair at home, it’s important to know how to respond to anaphylaxis if it occurs. Call 911 or have someone take you to the nearest ER if you develop symptoms such as trouble breathing or swelling of the face or throat.

10. Increased risk of cancer

There have been some concerns about Xolair raising the risk of cancer. This is because a variety of cancers were reported by some people receiving it in initial clinical trials. However, newer studies and other analyses involving over 40,000 people haven’t found an increased risk of cancer with Xolair.

Still, it’s important to play it safe. If you have a history of cancer, or believe you’re at a higher risk for developing cancer, speak to your healthcare provider. They can help you decide if Xolair is right for you.

When should you contact your prescriber about Xolair side effects?

Xolair is generally well tolerated, with many side effects only lasting a few days after receiving a dose. But you should tell your prescriber if any side effects become bothersome or don’t seem to be getting better. There may be an underlying cause that requires treatment.

Symptoms such as abdominal pain and diarrhea may indicate a parasitic infection. A healthcare professional can check your stool to confirm and provide treatment. You should also let your prescriber know right away if you develop joint pain with fever, rash, and swollen lymph nodes.

While rare, serious side effects that require immediate medical attention are possible. If you think you might be having a severe allergic reaction to Xolair, call 911 or go to the nearest ER.

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Written by:

Kristianne Hannemann, PharmD

Kristianne Hannemann, PharmD, is a licensed pharmacist in California. She has been a retail pharmacy manager and staff pharmacist for over 7 years and has contributed drug information content to different health companies.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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