Some people using omalizumab have had a severe, life-threatening allergic reaction either right after the injection or hours later. An allergic reaction may occur even after using omalizumab regularly for a year or longer.
Get emergency medical help if you have signs of an allergic reaction: hives, itching; anxiety or fear; flushing (warmth, redness, or tingly feeling); feeling like you might pass out; chest tightness, wheezing, cough, feeling short of breath, difficult breathing; fast or weak heartbeats; swelling of your face, lips, tongue, or throat.
Before taking this medicine
You should not use omalizumab if you are allergic to it.
Tell your doctor if you have any signs of infection (fever, swollen glands, general ill feeling), or if you have ever had:
any other allergies (foods, pollens, etc);
allergy shots;
a severe allergic reaction (anaphylaxis);
an infection caused by parasites (such as giardia, malaria, leishmaniasis, hookworm, pinworm, toxoplasmosis, and many others);
a heart attack or stroke;
cancer; or
a latex allergy.
Using  omalizumab may increase your risk of certain types of cancers of the breast, skin, prostate, or salivary gland. Talk to your doctor about your individual risk.
While you are using omalizumab, you may also have an increased risk of becoming infected with parasites (worms) if you live in or travel to areas where such infections are common. Talk with your doctor about what to look for and how to treat this condition.
Some babies born to mothers using omalizumab during pregnancy had low birth weight. However, it is not known whether this was due to omalizumab use or to severe asthma in the mothers. The benefit of treating asthma may outweigh any risks to the baby. Tell your doctor if you are pregnant.
If you are pregnant, your name may be listed on a pregnancy registry to track the effects of omalizumab on the baby.
It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.
