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7 Common and Serious Side Effects of Xolair

Alan Lucks | MD

Medically reviewed by Alan Lucks | MD, Alan Lucks MDPC Private Practice - New York on December 19th, 2025.

Key Takeaways

  • Xolair is a medication used for asthma, nasal polyps, and chronic hives, but it can cause both common and serious side effects.

  • Common side effects include injection site reactions, headaches, dizziness, and fatigue.

  • Serious side effects, such as anaphylaxis, cancer, and cardiovascular issues, require immediate medical attention.

  • Managing side effects often involves symptom relief and close monitoring.

  • Doctronic.ai offers personalized advice and telehealth visits to help you understand and manage Xolair side effects effectively.

Understanding Xolair Side Effects

Xolair (omalizumab) is a biologic medication primarily prescribed for moderate-to-severe allergic asthma and chronic spontaneous urticaria (hives). It works by blocking immunoglobulin E (IgE), a key player in allergic reactions. Xolair comes with potential side effects ranging from mild discomfort to serious health risks.

Knowing what to expect can help you manage symptoms better and seek timely care when necessary. This article breaks down common and serious side effects of Xolair, how to handle them, and when to contact a healthcare professional.

1. Injection Site Reactions

The most frequently reported side effect of Xolair is injection site reactions. These can include redness, swelling, pain, or itching where the shot was given. Usually, these symptoms appear within a few hours after the injection and may last a couple of days.

This reaction happens because the body responds to the needle or the medication itself. While uncomfortable, it’s generally not dangerous. Applying a cold compress and avoiding scratching can help ease the symptoms.

2. Headache

Many people using Xolair report headaches as a common side effect. These headaches can vary in intensity and may occur shortly after an injection or develop gradually over time.

Headaches may result from the body's immune response to the medication or changes in inflammation levels. Over-the-counter pain relievers often provide relief, but persistent or severe headaches should be discussed with a healthcare provider.

3. Fatigue

Feeling unusually tired or fatigued is another common complaint among Xolair users. This side effect can affect daily activities and overall quality of life.

Fatigue may be linked to the body's adjustment to the medication or the underlying condition being treated. Rest, hydration, and balanced nutrition can help manage this symptom. If fatigue worsens or is accompanied by other concerning signs, medical advice is recommended.

4. Allergic Reactions and Anaphylaxis

Though rare, serious allergic reactions to Xolair can occur. These may include symptoms such as swelling of the face, lips, tongue, or throat, difficulty breathing, rapid heartbeat, dizziness, or severe rash.

Anaphylaxis is a life-threatening emergency requiring immediate treatment. Patients starting Xolair are usually monitored for a period after their injection to catch any early signs. If you experience symptoms of an allergic reaction, seek emergency medical care without delay.

Recognizing Early Signs

  • Hives or itching beyond the injection site

  • Shortness of breath or wheezing

  • Swelling in the throat or mouth

  • Feeling faint or dizzy

Early recognition and prompt action can prevent serious complications.

5. Cardiovascular Effects

Some patients have reported cardiovascular side effects such as chest pain, palpitations, or irregular heartbeat while on Xolair. These symptoms may indicate underlying heart issues or be related to the medication’s impact on the immune system.

Any new or worsening chest discomfort should be evaluated promptly by a healthcare professional to rule out serious conditions like a heart attack or arrhythmias.

6. Joint and Muscle Pain

Muscle aches and joint pain can occur during Xolair treatment. These symptoms may be mild or moderate and typically improve over time.

Such pain might be caused by immune system changes or inflammation. Gentle exercise, stretching, and over-the-counter pain relief can be helpful. Persistent or severe pain should be reported to your doctor.

7. Increased Risk of Infections

Because Xolair modulates the immune system, it can slightly increase the risk of infections such as sinus infections, bronchitis, or upper respiratory infections.

Maintaining good hygiene and promptly addressing any signs of infection, such as fever, cough, or sore throat, is important. If infections become frequent or severe, medical evaluation is necessary.

Close-up of a syringe needle with a droplet of liquid against a blue backgroundHow to Manage and Reduce Side Effects of Xolair

Monitor Injection Site Care

Use a cold pack on the injection site to reduce swelling and discomfort. Avoid scratching to prevent irritation or infection. If redness or pain worsens, consult your healthcare provider.

Address Headaches and Fatigue

Stay hydrated and rest as needed. Over-the-counter pain relievers may help with headaches. If fatigue interferes with daily life, discuss alternative treatment options or supportive care with your doctor.

Stay Alert for Allergic Reactions

Always monitor for early signs of allergic reactions after injections. Having an emergency action plan and access to medical care are essential. Inform your healthcare provider immediately if you notice any symptoms.

Report New or Worsening Symptoms

Any new chest pain, palpitations, severe joint pain, or signs of infection should be promptly reported to a medical professional. Early intervention can prevent complications.

Xolair Allergic Reactions and Warnings

Xolair carries a boxed warning for the risk of anaphylaxis. Patients must be observed for at least two hours after the first three injections and for 30 minutes after subsequent doses. This precaution is critical for the early detection and treatment of severe allergic reactions.

Inform your healthcare provider about any history of allergies or previous reactions to medications. Also, discuss all other medications and supplements you are taking to avoid interactions.

When to Contact Your Doctor About Xolair Side Effects

  • Difficulty breathing, swallowing, or severe swelling

  • Chest pain or irregular heartbeat

  • Severe headache or persistent fatigue

  • Signs of infection, such as fever, chills, or a persistent cough

  • Severe or worsening injection site reactions

Prompt communication with your healthcare provider ensures safety and effective management of side effects.

Learn More About Xolair Side Effects With Doctronic

Understanding and managing medication side effects can be challenging. Doctronic.ai offers an innovative AI-powered doctor experience that provides personalized, up-to-date medical guidance tailored to your unique health profile. Whether you have questions about Xolair side effects or want advice on symptom management, Doctronic is available 24/7 for convenient telehealth video visits under $40 nationwide.

With over 10 million users, Doctronic combines the latest peer-reviewed medical research with personalized care, remembering your history and preferences. Visit Doctronic.ai to get fast, smart, and personal medical advice from anywhere.

The Bottom Line About Xolair Side Effects

Xolair is a powerful medication that can significantly improve symptoms for people with allergic asthma and chronic hives. Like all treatments, it carries the risk of side effects, ranging from mild injection site discomfort to rare but serious allergic reactions.

Being informed about these side effects, monitoring your health closely, and seeking timely medical advice can help you use Xolair safely and effectively. Leveraging telehealth services like Doctronic.ai can make managing your treatment easier, providing expert guidance whenever you need it.

Frequently Asked Questions

Weight gain is not commonly reported as a side effect of Xolair. If you notice unexplained weight changes, consult your healthcare provider to explore other causes.

Injection site reactions typically occur within hours. Allergic reactions can happen immediately or within a few hours post-injection. Other side effects, like headaches or fatigue, may develop over days.

Mild side effects such as injection site redness or mild headache often improve with time. Always discuss any side effects with your doctor before continuing treatment.

Many side effects can be managed with home care, like cold compresses, rest, and hydration. Serious symptoms require prompt medical attention.

Doctronic.ai offers personalized, evidence-based information on side effects and ways to reduce them. You can also schedule affordable telehealth visits with licensed doctors for tailored advice and treatment.

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