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Generic name: omalizumab [ OH-ma-LIZ-oo-mab ]
Brand names: Xolair, Xolair Prefilled Syringe
Dosage forms: subcutaneous powder for injection (150 mg), subcutaneous solution (150 mg/mL; 75 mg/0.5 mL)
Drug class: Selective immunosuppressants

Medically reviewed by Philip Thornton, DipPharm. Last updated on Sep 27, 2023.

What is omalizumab?

Omalizumab is an antibody that helps decrease allergic responses in the body.

Omalizumab is used to treat moderate to severe asthma that is caused by allergies in adults and children who are at least 6 years old. It is used when asthma symptoms are not controlled by asthma inhaled steroid medicine. Omalizumab is not a rescue medicine for treating an asthma attack.

Omalizumab is used to treat chronic hives (idiopathic urticaria) in adults and children who are at least 12 years old, after antihistamines have been tried without success.

Omalizumab is also used to treat nasal polyps in people 18 years of age and older when lled nasal corticosteroid medicines have not worked well.

Omalizumab is not for use in treating other allergies, rashes, or attacks of bronchospasm.


Some people using this medicine have had a severe, life-threatening allergic reaction either right after the injection or hours later. Allergic reaction may occur even after using omalizumab regularly for a year or longer.

Get emergency medical help if you have any signs of an allergic reaction to omalizumab: hives, rash; anxiety or fear; flushing (warmth, redness, or tingly feeling); feeling like you might pass out; chest tightness, wheezing, feeling short of breath, difficult breathing; fast or weak heartbeats; swelling of your face, lips, tongue, or throat.

Asthma is often treated with a combination of different drugs. Use all medications as directed by your doctor. Read the medication guide or patient instructions provided with each medication. Do not change your doses or medication schedule without your doctor's advice.

If you also use an oral steroid medication, do not stop using the steroid suddenly or you may have unpleasant withdrawal symptoms. Talk with your doctor if any of your asthma medications do not seem to work as well in treating or preventing attacks. Your symptoms may not improve right away once you start receiving omalizumab. For best results, keep receiving omalizumab as directed. Talk with your doctor if your symptoms do not improve after a few weeks of treatment.

Use omalizumab regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.

Before taking this medicine

You should not use omalizumab if you are allergic to it.

Tell your doctor if you have any signs of infection (fever, swollen glands, general ill feeling), or if you have ever had:

Using omalizumab may increase your risk of certain types of cancers of the breast, skin, prostate, or salivary gland. Talk to your doctor about your individual risk.

While you are using omalizumab, you may also have an increased risk of becoming infected with parasites (worms) if you live in or travel to areas where such infections are common. Talk with your doctor about what to look for and how to treat this condition.

Some babies born to mothers using omalizumab during pregnancy had low birth weight. However, it is not known whether this was due to use of this medicine or to severe asthma in the mothers. The benefit of treating asthma may outweigh any risks to the baby. Tell your doctor if you are pregnant.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of omalizumab on the baby.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

How is omalizumab given?

Omalizumab is injected under the skin. A healthcare provider will give you this injection every 2 or 4 weeks.

Your doctor may perform an allergy skin test or blood test to make sure this medicine is right for you.

Your condition may not improve right away. For best results, keep receiving omalizumab as directed. Talk with your doctor if your symptoms do not improve after a few weeks of treatment.

Omalizumab doses are based on weight. Your dose needs may change if you gain or lose weight.

If you also use a steroid medication, you should not stop using it suddenly. Follow your doctor's instructions about tapering your dose.

Seek medical attention if your breathing problems get worse quickly, or if you think your asthma medications are not working as well.

You may need frequent medical tests, such as allergy tests and lung function tests. Your stools may also need to be checked for parasites, especially if you travel.

What happens if I miss a dose?

Call your doctor for instructions if you miss an appointment for your omalizumab injection.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using omalizumab?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Omalizumab side effects

Some people using this medicine have had a severe, life-threatening allergic reaction to omalizumab, either right after the injection or hours later. Allergic reaction may occur even after using the medication regularly for a year or longer.

You will be watched closely for a short time after each injection, to make sure you do not have an allergic reaction to omalizumab.

Get emergency medical help if you have signs of an allergic reaction to omalizumab:

Call your doctor at once if you have:

Common omalizumab side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect omalizumab?

Other drugs may interact with omalizumab, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Popular FAQ

Xolair does act on the body’s immune system to prevent an allergic response, but because it only acts on the allergic arm of the immune system, it does not appear to compromise the immune system as other immunosuppressants do. Xolair is not like traditional immunosuppressants, such as prednisone or cyclosporine because it does not increase the risk of infection nor the risk of COVID-19. Continue reading

Free serum IgE levels are decreased within an hour of Xolair administration. However it may take several months for the full effects of Xolair to be seen, although some symptom improvement may be noted after a few weeks. Significant improvements were noted after 4 months in those with allergic asthma, after 3 months in those with chronic urticaria, and after 16 to 20 weeks in those with Ig-E-mediated food allergies.  Continue reading

Xolair works by preventing IgE from binding to IgE receptors on mast cells and basophils. This prevents mast cells and basophils from releasing histamine and heparin. Histamine narrows smooth muscle in the airways making it harder to breathe and also causes tissue swelling, itchy skin, hives, and other allergic-type symptoms. Heparin makes it harder for blood to clot. Continue reading

There were no reports of weight gain or weight loss in clinical trials with Xolair. Weight gain is more likely to be caused by corticosteroids, hydroxyzine, or antihistamines that may also be used to treat allergic asthma or hives. Continue reading

The omalizumab mechanism of action is designed to target IgE (immunoglobulin E), an antibody produced by the immune system. It works by inhibiting the binding of the IgE antibody to IgE receptors on cells that can lead to inflammation and worsened allergic symptoms. Continue reading

If you are being treated with omalizumab, you can be vaccinated with the COVID-19 vaccination at any time, but the ACAAI (American College of Allergy, Asthma, and Immunology) recommends that the COVID-19 vaccine and omalizumab not be given on the same day since, if a reaction or a side effect occurs, it may be challenging to work out which injection was to blame. The ACAAI suggests separating the COVID-19 vaccination and omalizumab by at least 24 hours. There is no reason to stop omalizumab until you complete the course of the COVID-19 vaccinations. Continue reading

Yes, you or your caregiver can learn how to give Xolair at home if you and your doctor agree that self-injection is appropriate. For children 12 years of age and older, the Xolair prefilled syringe or autoinjector may be self-injected under adult supervision. For children 1 to 11 years of age, only the Xolair prefilled syringe should be used and injected by a caregiver, as the autoinjector is not intended for this age group. Continue reading

Xolair (generic name: omalizumab) is approved to treat asthma triggered by allergies, sinus inflammation with nasal polyps, chronic hives and to help reduce allergic reactions due to accidental exposure to certain foods (along with avoiding foods to which you are allergic). It is not used for the emergency treatment of allergic reactions, including anaphylaxis. Continue reading

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Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use omalizumab only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.