omalizumab
Omalizumab (Xolair) is a biologic medicine that binds to immunoglobulin E (IgE), the antibody that triggers allergic reactions. It is used as add-on therapy for moderate-to-severe allergic asthma, chronic spontaneous urticaria, chronic rhinosinusitis with nasal polyps, and to reduce allergic reactions from accidental food allergen exposure.
This page is based on EMA and FDA prescribing information for omalizumab, cross-checked with DailyMed labeling and the National Cancer Institute drug dictionary; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
IgE is like a match that lights off allergic reactions when it lands on mast cells. Omalizumab acts like a sponge that soaks up free IgE in the bloodstream before it can reach those cells, so the matches never land and the allergic fire stays out.
In simple terms
Omalizumab is an antibody that binds to free IgE, the type of antibody that drives allergic reactions. By lowering the amount of IgE circulating in the blood, omalizumab prevents IgE from attaching to mast cells and basophils — the cells that release histamine and other chemicals during an allergic response. With less IgE available, these cells become less reactive, which reduces asthma attacks, nasal polyp growth, and the hives and swelling of chronic urticaria. It also raises the threshold for allergic reactions to foods, so accidental exposure is less likely to trigger a severe response.
In depth
Omalizumab is a recombinant DNA-derived humanized IgG1 monoclonal antibody that selectively binds to the C-epsilon 3 domain of free IgE, the same site through which IgE attaches to the high-affinity receptor FcεRI on mast cells and basophils. By binding circulating IgE, omalizumab reduces free serum IgE levels by more than 95% and triggers down-regulation of FcεRI on these effector cells. The resulting decrease in mast cell and basophil reactivity reduces release of histamine, leukotrienes, and other inflammatory mediators that drive allergic asthma, chronic spontaneous urticaria, and nasal polyp inflammation. In IgE-mediated food allergy, omalizumab raises the threshold for mast cell activation, reducing the severity of reactions to accidental allergen exposure.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
IgE is like a match that lights off allergic reactions when it lands on mast cells.
- Omalizumab is an antibody that binds to free IgE, the type of antibody that drives allergic reactions.
- By lowering the amount of IgE circulating in the blood, omalizumab prevents IgE from attaching to mast cells and basophils — the cells that release histamine and other chemicals during an allergic response.
- With less IgE available, these cells become less reactive, which reduces asthma attacks, nasal polyp growth, and the hives and swelling of chronic urticaria.
- It also raises the threshold for allergic reactions to foods, so accidental exposure is less likely to trigger a severe response.
Target: Immunoglobulin E (IgE)
The antibody class responsible for immediate (Type I) allergic reactions; omalizumab binds free IgE in the blood, lowering the amount available to attach to mast cells and basophils and thereby reducing allergic activation.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in European Union
EMA- Add-on therapy to improve asthma control in adults, adolescents, and children (6 to <12 years) with severe persistent allergic asthma who have a positive skin test or in vitro reactivity to a perennial aeroallergen, reduced lung function, frequent daytime symptoms or night-time awakenings, and multiple documented severe exacerbations despite daily high-dose inhaled corticosteroids plus a long-acting inhaled beta2-agonist.
- Add-on therapy with intranasal corticosteroids for the treatment of adults with severe chronic rhinosinusitis with nasal polyps for whom therapy with intranasal corticosteroids does not provide adequate disease control.
- Add-on therapy for the treatment of chronic spontaneous urticaria in adult and adolescent (12 years and above) patients with inadequate response to H1 antihistamine treatment.
Approved uses in United States
FDA- Moderate to severe persistent asthma in adults and pediatric patients 6 years of age and older with a positive skin test or in vitro reactivity to a perennial aeroallergen and symptoms that are inadequately controlled with inhaled corticosteroids.
- Chronic rhinosinusitis with nasal polyps in adult patients 18 years of age and older with inadequate response to nasal corticosteroids, as add-on maintenance treatment.
- IgE-mediated food allergy in adult and pediatric patients aged 1 year and older for the reduction of allergic reactions (Type I), including anaphylaxis, that may occur with accidental exposure to one or more foods, to be used in conjunction with food allergen avoidance.
- Chronic spontaneous urticaria in adults and adolescents 12 years of age and older who remain symptomatic despite H1 antihistamine treatment.
Approved uses in United States
DailyMed- Adults and pediatric patients 6 years of age and older with moderate to severe persistent asthma who have a positive skin test or in vitro reactivity to a perennial aeroallergen and whose symptoms are inadequately controlled with inhaled corticosteroids.
- Add-on maintenance treatment of chronic rhinosinusitis with nasal polyps in adult patients 18 years of age and older with inadequate response to nasal corticosteroids.
- Reduction of allergic reactions (Type I), including anaphylaxis, that may occur with accidental exposure to one or more foods in adult and pediatric patients aged 1 year and older with IgE-mediated food allergy, to be used in conjunction with food allergen avoidance.
- Treatment of adults and adolescents 12 years of age and older with chronic spontaneous urticaria who remain symptomatic despite H1 antihistamine treatment.
Official sources
The statements on this page trace back to these records.
- Xolair (omalizumab) — Summary of product characteristics and package leaflet, English version
European Medicines Agency
- U.S. Food and Drug Administration: omalizumab prescribing information
U.S. Food and Drug Administration
- DailyMed: XOLAIR labeling
DailyMed, U.S. National Library of Medicine
- National Cancer Institute: omalizumab
National Cancer Institute
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.