Some people using omalizumab have had a severe, life-threatening allergic reaction either right after the injection or hours later. Allergic reaction may occur even after using the medication regularly for a year or longer.
You will be watched closely for a short time after each injection, to make sure you do not have an allergic reaction to omalizumab.
Get emergency medical help if you have signs of an allergic reaction:
hives, itching;
anxiety or fear, feeling like you might pass out;
flushing (warmth, redness, or tingly feeling);
chest tightness, wheezing, cough, feeling short of breath, difficult breathing;
fast or weak heartbeats; or
swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
ongoing nausea or vomiting, severe or watery diarrhea;
trouble breathing;
numbness or tingling in your arms or legs;
fever, muscle pain, and rash within a few days after receiving an injection;
signs of an ear infection--fever, ear pain or full feeling, trouble hearing, drainage from the ear, fussiness in a child;
heart attack symptoms--chest pain or pressure, pain spreading to your jaw or shoulder; or
signs of a blood clot--sudden numbness or weakness, problems with vision or speech, coughing up blood, swelling or redness in an arm or leg.
Common side effects may include:
rash;
fever;
nosebleeds;
joint pain, bone fractures;
arm or leg pain;
nausea, vomiting, diarrhea, stomach pain;
headache;
dizziness, feeling tired;
ear pain, ear infection;
pain, bruising, swelling, or irritation where the medicine was injected; or
cold symptoms such as stuffy nose, sneezing, sinus pain, cough, sore throat.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Omalizumab side effects (more detail)
