Key takeaways:
Xolair (omalizumab) is an injectable medication used for chronic allergy-related conditions. It has few known drug interactions. But you should still review your full medication list with your prescriber before starting treatment.
Taking Xolair with other immunotherapy medications or immunosuppressants may raise your risk of infections or affect how these treatments work. Your prescriber may want to check you more often for signs or symptoms of an infection.
You can combine Xolair with Dupixent (dupilumab) or other biologics in some cases, but only under medical guidance. Antihistamines are generally safe to take with Xolair.
Save on related medications
Xolair (omalizumab) is an injectable medication that treats chronic allergy-related conditions. It doesn’t have many drug interactions, but there are a few things to be aware of while you’re receiving it.
Knowing which interactions to watch for can help you avoid unwanted side effects. You’ll also be able to make sure your treatment works as well as it should.
Keep in mind that Xolair interactions haven’t been well-studied. Your prescriber can help determine whether these interactions are an issue for you based on your personal history. Be sure to show them a complete list of the medications you’re taking.
1. Other immunotherapy-based treatments
Xolair is a form of immunotherapy. This means it works by affecting your immune system. Xolair decreases a specific type of immune response by blocking an antibody called immunoglobulin E (IgE).
Other immunotherapy medications can work in different ways. For example, some increase immune system activity to target certain cancer cells.
Combining Xolair with other immunotherapy medications that work in a similar way may increase your risk of side effects, such as infection. But if an immunotherapy medication requires IgE to work properly, Xolair could make it less effective. IgE-based treatments aren’t common, but they could be available within the next few years.
Be sure to tell your prescriber that you’re receiving Xolair before starting any new immunotherapy-based medications. They can help determine if there’s any type of interaction that should be addressed.
2. Immunosuppressants
Immunosuppressants can weaken the immune system. They’re different from immunotherapy in that they aren’t a targeted treatment. Instead, they decrease immune system activity more broadly to reduce inflammation and other symptoms. Common examples of immunosuppressants include:
Corticosteroids, such as prednisone
Traditional chemotherapy (not immunotherapy)
Xolair isn’t an immunosuppressant. But it can raise the risk of certain infections. Combining it with an immunosuppressant may further increase your infection risk. This doesn’t mean you can’t take Xolair with an immunosuppressant. But your prescriber may have you keep a closer eye out for signs or symptoms of an infection. Let them know if you develop a fever, a persistent cough, or localized redness and swelling.
Can you take Xolair and Dupixent together?
Combining Xolair with Dupixent (dupilumab) isn’t common. But in some cases your prescriber may recommend it. Dupixent is a biologic that treats inflammatory conditions such as eczema and asthma. It targets proteins called cytokines that lead to inflammation.
Xolair and Dupixent work in different ways. So combining them may help reduce the symptoms of conditions associated with high IgE levels if one medication isn’t effective on its own.
Xolair also seems to be safe to combine with other biologics that treat inflammatory conditions, such as Humira (adalimumab). But you should take Xolair with another biologic medication only if your prescriber recommends it.
Can you take Xolair with antihistamines?
Antihistamines are often used to treat allergy-related symptoms. These include Claritin (loratadine) and Benadryl (diphenhydramine). It’s fine to take an antihistamine if you’re also receiving Xolair — especially if you have an allergic reaction. That’s because Xolair prevents allergic reactions but doesn’t treat them if they occur.
Keep in mind that different types of antihistamines have distinct side effects and other interactions. So ask your prescriber or pharmacist which option is the best for you.
Good to know: If you’re taking a daily antihistamine to help manage a chronic allergic condition, you may be able to reduce your dose or stop taking it after you start Xolair. Your prescriber can tell you how to stop your antihistamine safely if this applies to you.
The bottom line
Xolair (omalizumab) is an injectable medication that treats chronic allergy-related conditions. It has few known drug interactions, but some combinations require caution. Interaction data is limited, so it’s important to share your medication list with your prescriber so they can help you use Xolair safely and effectively.
Combining Xolair with other immunotherapy medications or immunosuppressants may increase your risk of infections or change how well certain treatments work. Your prescriber may recommend closer monitoring for signs or symptoms of infection if you’re taking these medications together.
In some cases, Xolair may be combined with other biologics, such as Dupixent (dupilumab). But this should occur only under medical guidance. Antihistamines are generally safe to take with Xolair, especially to treat active allergy symptoms.
Why trust our experts?
References
Genetech. (2025). Xolair- omalizumab injection, solution [package insert].
Inside Precision Medicine. (2025). IgE antibody therapy offers hope for hard-to-treat breast and ovarian cancers.
Keow, S., et al. (2025). Patient outcomes and safety of combination biologic therapy with dupilumab. Annals of Asthma, Allergy & Immunology.
Kumari, S., et al. (2025). IgE based therapeutics are an emerging modality in cancer treatment. Discover Oncology.
Patel, P., et al. (2024). Immunotherapy. StatPearls.
Rezwan, T., et al. (2025). Correlation between total IgE level and asthma symptom severity in hospitalized children. Journal of Allergy and Clinical Immunology: Global.
Silva, I. C., et al. (2025). Combined use of omalizumab and dupilumab: Safety and efficacy data from a large academic center. Archives of Dermatological Research.
Wollenberg, A., et al. (2021). Targeting immunoglobulin E in atopic dermatitis: A review of the existing evidence. World Allergy Organization Journal.
Yıldırım, S. K., et al. (2023). Omalizumab treatment in combination with any other biologics: Is it really a safe duo? Australasian Journal of Dermatology.
