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What is omalizumab's mechanism of action?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on June 3, 2022.

Official answer


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.

When IgE binds to the IgE receptor, mast cells release the chemical histamine and can cause inflammatory reactions and allergic reactions. Histamine can cause blood vessels to expand and lead to itching and swollen skin. It can also cause the breathing tubes to narrow and create a build-up of mucus.

Asthma and wheezing symptoms, runny nose, watery eyes, skin swelling, itching or redness, and hives can occur. Histamine can also cause anaphylaxis, a severe and potentially life-threatening allergic reaction.

Higher amounts of IgE antibody in your blood can mean that you might overreact to allergens or histamine. Your doctor may test your blood for levels of IgE before you start treatment with omalizumab. By blocking IgE binding, your allergic symptoms can improve.

How does omalizumab work in allergies?

Omalizumab (brand name: Xolair) is approved by the FDA to treat asthma, nasal polyps and chronic hives (also called chronic spontaneous urticaria).

  • Omalizumab is given as a subcutaneous (under the skin) injection and is used when other treatments have not been effective to control your symptoms.
  • Xolair is given in 1 or more injections under the skin (subcutaneous), 1 time every 2 or 4 weeks. Your doctor will determine your dose. Your doctor will administer your first few doses, and then, if approved by your doctor, you or your caregiver can be trained to give the Xolair dose at home using a prefilled syringe.
  • It is not used to treat other allergic conditions, other forms of hives, or sudden breathing problems.

Allergic Asthma

Reactions to an airborne allergen like pet dander, dust mites or cockroach debris can occur in allergic asthma, leading to release of IgE. In allergic asthma, even small amounts of IgE can lead to an inflammatory and allergic response.

Omalizumab is approved to treat moderate-to-severe asthma that is caused by allergies in adults and children 6 years of age and older. Your doctor will give you an IgE blood test or a skin test to see if you have year-round allergies and to determine your dose.

Omalizumab is not typically used as your first medicine if you have asthma. It is used when your asthma symptoms are not controlled by an inhaled corticosteroid (“steroid”).

Omalizumab is not used as a rescue medicine for sudden breathing problems in asthma.

Nasal Polyps

Nasal polyps are benign growths (not caused by cancer) located in the inside of your nose. The polyps are caused by long-term swelling in your nasal passages, possibly due to allergies. Omalizumab treatment can help to decrease the size of the polyps and nose congestion.

Omalizumab is approved to treat nasal polyps in people 18 years of age and older when nasal corticosteroids have not been effective. Your doctor will give you an IgE blood test to see if you have year-round allergies.

Chronic Hives

Chronic spontaneous urticaria (formerly known as chronic idiopathic urticaria) is chronic hives that last 6 weeks or longer and has no known cause. You do not need an IgE blood test to determine your dose if you have chronic hives.

Omalizumab is used to treat chronic spontaneous urticaria (chronic hives) in people 12 years of age and older who continue to have hives that are not controlled with H1 antihistamine treatments.

This is not all the information you need to know about omalizumab (brand name: Xolair) for safe and effective use and does not take the place of your doctor’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.


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