What is omalizumab and what is it used for?

Omalizumab is an injectable medication used for the treatment of severe allergic asthma. Omalizumab is a man-made protein that is similar to natural proteins produced by the body and it belongs to a class of medicines called monoclonal antibodies. The main ingredient in Xolair is called omalizumab.

How omalizumab works

When you have severe allergic asthma, inflammation occurs due to your body’s natural immune system overreacting to triggers such as animal hair, mould spores or dust mites. Omalizumab works by blocking immunoglobulin E (IgE) which is a molecule produced by the body. IgE plays a key role in causing allergic asthma.

For more information about how omalizumab works, please click below.

Download guide

What to expect from omalizumab

Although responses to omalizumab can vary, studies of people using omalizumab have demonstrated:

  • Reductions in asthma attacks and hospitalisations,
  • Improvements in asthma symptoms and asthma-related quality of life.

Omalizumab will only ever be prescribed for the treatment of severe allergic asthma. Omalizumab SHOULD NOT BE USED to treat any other types of asthma.

We recommend keeping track of your severe allergic asthma-related symptoms and any impact they are having on your day-to-day life. This will allow your doctor to see the effect omalizumab is having and then act accordingly.

Click below to download the asthma symptom tracker questionnaire.

Download Questionnaire

How to take omalizumab

Omalizumab comes in a pre-filled syringe that will initially be administered by your doctor or nurse. If possible, your doctor, nurse or pharmacist will train you on how to administer omalizumab independently.


Icon of a targetThe injection site is the place on the body where you are going to use the syringe.

The injection site should be clean and sterile. It is recommended to use an alcohol wipe before injecting.

The recommended site is the front of the thighs. You can also use the lower abdomen, but not within 5 centimetres of your navel (belly button).

If you need to give more than one injection for the full dose, choose a different injection site each time you inject.

Do not inject into areas where the skin is tender, bruised, red or hard. Avoid areas with scars or sketch marks.

If a caregiver is administering the injection, the outer upper arm may also be used as an injection site.

There are several possible injection sites that you can use for your injections. Choose the sites that are the most comfortable for you.

Your omalizumab dose is tailored specifically for you and is calculated using your body weight and the level of IgE in your blood. If your weight changes significantly you should speak to your doctor or nurse as they may need to recalculate your dose.

Icon of an egg timer

  1. Take the box containing the syringe out of the refrigerator and leave it unopened for about 20 minutes so that it reaches room temperature (leave the syringe in the box to protect it from light).
  2. When you are ready to use the syringe, wash your hands thoroughly with soap and water.
  3. Clean the injection site with an alcohol swab.
  4. Remove the plastic tray from the box and peel back the paper cover. Gripping the middle of the purple or blue syringe guard, lift the syringe out of the tray. Be careful not to touch the syringe guard wings, as this may activate the syringe guard too early.
  5. Inspect the syringe. The liquid should be clear to slightly cloudy. Its colour may vary from colourless to pale brownish yellow. You may see an air bubble, which is normal. DO NOT USE if the syringe is broken or if the liquid looks cloudy or distinctly brown or contains particles. In all these cases, return the entire pack to the pharmacy.
  6. Holding the syringe horizontally, look into the viewing window to check the expiry date printed on the label. Be careful not to touch the syringe guard wings. Note: It is possible to rotate the inner part of the syringe assembly so that the label can be read in the viewing window. DO NOT USE if the product has expired. In this case, return the entire pack to the pharmacy.

Icon of a syringe

  1. Carefully remove the needle cap from the syringe. Discard the needle cap. You may see a drop of liquid at the end of the needle. This is normal.
  2. With one hand, gently pinch the skin at the injection site and insert the needle. Push the needle all the way in to ensure that the medicine can be fully administered. When you insert the needle, ensure the bevel (the hole in the needle) is facing upwards.
  3. Hold the syringe by the finger grips with your thumb on the plunger. Slowly depress the plunger as far as it will go so that the plunger head is completely between the syringe guard wings.
  4. Keep the plunger fully depressed, while you carefully lift the needle straight out from the injection site.
  5. Slowly release the plunger and allow the syringe guard to automatically cover the exposed needle.


There may be a small amount of blood at the injection site. You can press a cotton ball or gauze over the injection site and hold it for 30 seconds. Do not rub the injection site. You may cover the injection site with a small adhesive dressing, if needed.

Icon of a disposal bin

  1. Dispose of the used syringe immediately in a sharps container (closable, puncture-resistant container). For the safety and health of you and others, needles and used syringes must never be reused. Any unused medicinal product or waste material should be disposed of in accordance with local requirements.

For more information about how to self-inject Omalizumab, please click below. 

Download guide

Warnings and precautions

Talk to your doctor before using omalizumab:

  • If you have kidney or liver problems.
  • If you have a disorder where your own immune system attacks parts of your own body (autoimmune disease).
  • If you are travelling to a region where infections caused by parasites are common.
  • Omalizumab may weaken your resistance to such infections.
  • If you have had a previous severe allergic reaction (anaphylaxis), for example resulting from a medicine, an insect bite or food.
  • If you have ever had an allergic reaction to latex. The needle cap of the syringe may contain dry rubber (latex).
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UK | February 2022 | 171377

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Reporting of side effects
If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet. You should also report side effects directly via the Yellow Card Scheme at yellowcard.mhra.gov.uk.
By reporting side effects you can help provide more information on the safety of this medicine.