How Long Does Xolair Take to Work? Plus, 8 Other FAQs

Xolair (omalizumab) is an injectable medication that can offer relief from chronic allergy-related conditions when other treatments haven’t worked. If you’re prescribed Xolair for allergic asthma, chronic hives, or another allergy-related condition, your healthcare team will likely walk you through the basics. This includes guidance on how to inject Xolair and what side effects to expect.

But it’s common to have other questions, such as how long does Xolair take to work? And does it suppress the immune system? Here, we’ll answer nine frequently asked questions about Xolair to help you get the most from this medication.

1. How long does Xolair take to work?

Based on studies, Xolair can start working as soon as 4 weeks (1 month) after starting treatment — and possibly even sooner. But it may take as long as 16 weeks (4 months) to feel its full effects.

Here’s how long it usually takes for Xolair to start working for different health conditions based on clinical studies:

• Allergic asthma: 4 to 16 weeks

• Chronic rhinosinusitis with nasal polyps (CRSwNP): 4 to 16 weeks

• Chronic hives of unknown cause: 4 (or less) to 12 weeks

• To reduce the risk of food allergies: 16 weeks

Your prescriber can talk to you about when you should expect to see benefits from Xolair. In addition to a timeline, they can also let you know what to look for to help you determine if Xolair is effective for you.

If you’re not feeling any benefits after several months of Xolair treatment, your prescriber can determine if you should continue using it or switch to a different medication.

2. How does Xolair work?

Xolair works by blocking an antibody called immunoglobulin E (IgE). IgE is a key driver of allergic reactions in the body. It activates mast cells and other immune system pathways, leading to a release of histamine and other substances that trigger inflammation and other allergy-related symptoms.

Xolair blocks IgE from activating immune cells, which helps prevent allergic reactions and reduces allergy-related symptoms.

3. Can you inject Xolair at home?

Yes, you may be able to administer Xolair injections at home. But you’ll receive at least 3 doses in a healthcare setting first. This is because in rare cases, Xolair can cause a severe allergic reaction called anaphylaxis. This type of reaction usually happens within 1 to 2 hours of receiving your first few doses of Xolair. Receiving them in a healthcare setting helps ensure you can receive treatment right away if anaphylaxis occurs.

Keep in mind that it’s still possible to have a reaction to Xolair after your first few doses. So your prescriber will also make sure you know the signs and symptoms of anaphylaxis and what steps to take if it occurs before you begin giving yourself Xolair injections at home.

Xolair comes in a prefilled syringe and autoinjector. But the autoinjector is only FDA approved for adults and children ages 12 and older. You can inject either form of Xolair subcutaneously (under the skin) into your thigh or stomach. The upper arm is also an option if someone else is giving you the injection.

EXPERT PICKS: WHAT TO READ NEXT

• Xolair for food allergies: People with food allergies may accidentally be exposed to allergens. Learn how Xolair (omalizumab) can help lower the risk of having a serious allergic reaction to foods.

• Xolair side effects: Do you experience pain and redness after injecting Xolair? Here are common and rare Xolair side effects and how to manage them.

• How to inject Xolair: Pharmacists break down how to inject Xolair and other tips for using it.

4. Can Xolair make hives worse?

Xolair is approved to treat chronic hives, so it’s unlikely that it will make hives worse. Typical Xolair side effects include injection site reactions and headache. These are typically mild and resolve on their own.

That being said, some people have reported a worsening of hives after starting treatment with Xolair. But it’s not clear if Xolair alone was the cause. One of the inactive ingredients in Xolair, namely polysorbate, may be to blame. But if you develop new or worsening hives after receiving Xolair, it’s best to seek medical care right away. It could be a sign of an allergic reaction that requires prompt care.

5. Is Xolair a steroid?

No, Xolair isn’t a steroid.

Steroids, or corticosteroids, are a broad class of medications that treat different health conditions involving inflammation. Steroids can come in the form of oral pills, nasal sprays, and inhalers, among others. They’re often used for health conditions that are also treated by Xolair, such as asthma and CRSwNP. 

Steroids work by mimicking hormones in the body that reduce inflammation. They have a broad effect on the immune system and other pathways in the body related to inflammation. Because of this, many steroids have significant long-term side effects to consider when using them for extended periods of time.

As mentioned, Xolair targets IgE, a specific antibody involved in allergic responses. Since Xolair affects your immune system in a more targeted way than steroids do, it avoids most of these long-term risks.

6. Does Xolair suppress the immune system?

Xolair doesn’t appear to meaningfully suppress or weaken your immune system. Xolair targets IgE antibodies, which don’t seem to play a big role in fighting infections. IgE is mainly released in response to allergens, such as pollen or certain foods. IgE is also known to worsen conditions such as asthma, hives, and chronic sinus inflammation. This is why Xolair can help with these allergic conditions.

However, IgE may also play a role in helping the body fight off parasitic infections, such as roundworm and hookworm. Some people have reported  parasitic infections while using Xolair. But these individuals were already at a higher risk for these infections. So it isn’t clear whether or not Xolair carries this risk on its own.

If you’re concerned about Xolair’s effects on the immune system, talk with your prescriber. They can help you better understand your specific risks with Xolair and how to safely use the medication.

7. Does Xolair interact with other medications?

We don’t have a lot of information on Xolair interactions at this time. But because of its targeted effects, drug interactions aren’t common.

Still, it’s best to review your current medication list with your prescriber and pharmacist before starting Xolair. They can look for any potentially harmful interactions. It’s also best to check in with your healthcare team before starting any new medications or supplements while you’re receiving Xolair. This helps ensure your treatment plan is safe and effective.

8. Is Xolair a biologic?

Yes, Xolair is a biologic medication. Biologics are complex medications made from living sources. They often come as injections or infusions.

Xolair is one of several biologics for asthma and other allergy-related conditions. These biologics are typically only used when other treatments haven’t been effective. They also tend to cost more than other treatment options and have to be filled at specialty pharmacies (as we will discuss below).

Biologics also don’t have generic versions like traditional medications. Instead, they have biosimilars — medications that are highly similar to the original FDA-approved biologic (known as the reference product). Biosimilars provide the same clinical benefits, but they’re usually a bit more affordable than the reference product. Xolair has an approved biosimilar called Omlyclo (omalizumab-igec). But it likely won’t be commercially available until late 2026 at the earliest.

9. Is Xolair a specialty medication?

Yes, Xolair is considered a specialty medication. This means it’s only available through specialty pharmacies. 

Specialty pharmacies are unique because they manage medications that require highly specific handling, storage, and administration. Specialty medications are usually expensive and require extra steps, such as a prior authorization, for insurance coverage. They’re often shipped or delivered to your home rather than picked up in person.

If you’re prescribed Xolair, your healthcare team will help connect you with a specialty pharmacy that can help with insurance coverage as well as fill and deliver your medication. 

How to save on Xolair

There are ways to save on Xolair, which is available only as a reference (brand name) medication. GoodRx can help you navigate between copay savings cards and patient assistance programs to save money on your prescription. The following options can help you save on Xolair:

• Save with a copay savings card: If you have commercial insurance, you may be eligible to pay as little as $0 for Xolair using a savings card from the manufacturer.

• Save with patient assistance programs: If you’re uninsured or underinsured, you may be eligible for Xolair’s patient assistance program, which offers the medication free of charge.

• Save with biosimilars: In March 2025, the FDA approved Omlyclo, the first Xolair biosimilar. But it likely won’t be available in the U.S. until at least September 2026.

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Written by:

Austin Ulrich, PharmD, BCACP

​​Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. Ulrich’s experience includes direct patient care in hospital and community pharmacies.

Edited by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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