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Xolair Side Effects

Xolair, an injectable medication to treat allergic asthma and chronic hives, is linked to several serious, sometimes deadly, side effects. It has a warning for an increased risk of anaphylaxis (a severe, life-threatening allergic reaction). Xolair has also been linked to heart and brain blood-vessel problems, Xolair has been found to increase a patient’s risk of cancer.

Xolair is an injectable treatment for allergy-related illnesses, including allergic asthma and chronic hives that cannot be traced to a known cause. It is given once or twice a month by a physician or other medical professional in a health care setting.

black box warning on the drug’s label warns patients and health care professionals about the possibility of anaphylaxis, a serious allergic reaction that can lead to death very quickly. Additionally, the U.S. Food and Drug Administration evaluated a study that links the drug to heart complications as well as problems with the blood vessels in the brain.

But Xolair is also associated with some lesser known, but still very serious, side effects, including an increased risk of developing malignancies (cancer) affecting various parts of the body.

Use of the asthma medication is also found to cause a condition called vasculitis in some patients, which causes inflammation of blood vessels, blocking normal blood flow. Additionally, Xolair has been linked to an increased risk of parasitic infections and a combination of symptoms involving fever, joint pain and rash.

Malignancy (Cancer) in Xolair-Treated Patients

Malignant neoplasms (abnormal growths) were observed in 0.5 percent of patients treated with Xolair compared to 0.2 percent of untreated participants in a controlled clinical study, according to the drug’s label. The study involved adults and adolescents 12 and older who were diagnosed with asthma and other allergic disorders.

Dangerous Side Effect
The development of at least 10 different cancers have been observed in patients following the use of Xolair.

The malignancies that emerged in the patients taking Xolair varied, with breast, non-melanoma skin, prostate, melanoma and parotid (a major salivary gland located on either side of the mouth and in front of both ears) occurring more than once in observed patients, and five other types of cancer occurring once each.

Most of the patients participating in the study were observed for less than one year. Therefore, the impact of longer exposure to Xolair in treated patients at higher risk for malignancy, such as those who are older, current smokers, or otherwise), is unknown.

In a later observational study, where both Xolair-treated patients and non-Xolair-patients were followed for up to five years, results showed that malignancy outcomes were similar in both groups. However, it is noted that several study limitations prevent a definitive finding, meaning malignancy risk with Xolair cannot be completely ruled out.

Study limitations included:
  • Observational study design
  • Bias introduced by allowing enrollment of patients who had previously been exposed to Xolair (88 percent)
  • Enrollment of 56 percent of patients while a history of cancer or a premalignant condition were study exclusion criteria
  • High study discontinuation rate (44 percent of patients dropped out)

What Is a Malignancy?

A malignancy refers to the “presence of cancerous cells that have the ability to spread to other sites in the body (metastasize) or to invade nearby (locally) and destroy tissues,” as defined by the National Institutes of Health (NIH).

Unlike healthy cells, malignant (cancerous) cells tend to undergo very rapid, uncontrolled growth, and do not die as they should due to changes in their genetic makeup. Damaged and unneeded cells in the body typically die under normal circumstances when they are not considered to be malignant.

All of the extra cells can form a mass called a tumor. Cells from malignant tumors invade nearby tissues and can also break away and spread to other areas of the body. Cancer can affect almost any organ or tissue, such as the lungs, colon, breasts, skin, bones or nerve tissue.

Symptoms of Malignancy

Symptoms of cancer depend on the type of cancer affecting the patient and where it is located. For example, lung cancer can cause coughing, shortness of breath or chest pain, while colon cancer can cause diarrhea, constipation and bloody stools. However, there are some signs and symptoms of cancer that generally affect patients with all types of cancer.

  • Chills
  • Fever
  • Loss of appetite
  • Fatigue; feeling weak or very tired
  • Night sweats
  • Pain
  • Weight loss
  • General feeling of discomfort, uneasiness or illness
Other symptoms that may signal a problem specific to certain types of cancer, include:
  • Skin changes
  • Breast changes
  • Unusual vaginal bleeding
  • Abdominal pain
  • Difficulty urinating or painful urination; blood in urine
  • Hoarseness or cough that doesn’t go away
  • Changes in bowel habits
  • Thickening or lump on or under the skin
  • Difficulty eating; discomfort or trouble swallowing

Many of these symptoms can also be related to conditions that are not cancer. Benign tumors can cause symptoms similar to malignant tumors. However, it is important to note that early cancers usually do not cause pain as an initial sign of disease.

Diagnosis and Treatment of Malignancies (Cancer)

Various tests are used to diagnose different types of cancer, but most cancers are diagnosed by biopsy, or the removal of a small piece of tissue that is examined in a lab for the presence of cancerous cells.

Depending on the location of the tumor, a biopsy can be a simple outpatient procedure or a major surgery. Often, a CT scan will be done to determine the location and size of the tumor prior to a biopsy being performed.

Other tests can include blood tests, X-rays, MRI scans and PET scans (a scan that shows how organs and tissues are working).

Doctor holding an x-ray
A CT scan can determine the location and size of a tumor

Once a diagnosis has been made, treatment will vary based on the type of cancer and how advanced it is, or its stage. The stage of cancer depends on how much it has grown and if it has spread.

Treatment plans can include surgery, radiation and/or chemotherapy. Surgery is done to remove the cancer. This is most effective when the cancer has not spread. In cases where the malignancy is widespread throughout the body, or surgery alone cannot remove all of the cancer, radiation, chemotherapy and other treatments, such as immunotherapy and targeted cancer therapies, are also used.

A patient’s outlook is largely dependent on the type and stage of the cancer when diagnosed. Some cancers can be cured, while others can only be treated. Likewise, some patients can live for many years with cancer, while other tumors can lead to death quickly.

Also, malignant cells that are resistant to treatment can sometimes return even after they have all seemingly been removed or destroyed.

Xolair and Inflammation of Blood Vessels (Vasculitis)

Rare instances of serious systemic eosinophilia, sometimes presenting with the clinical features of vasculitis (inflammation in the blood vessels), have been reported in patients taking Xolair, according to its drug label. The severe reaction to the injectable asthma medication is consistent with a condition called Churg-Strauss syndrome and characterized by inflammation of the blood vessels occurring in patients with a history of asthma or allergy.

Eosinophilic disorders result from the build-up of too many eosinophils, a type of white blood cell, in various parts of the body. Eosinophils help to fight off infections and are important in the body’s immune response. When the body wants to attack a foreign substance that invades the body, such as an allergen, eosinophils jump into action by moving into the area of the substance and releasing toxins.

If an aneurysm bursts, it can lead to serious, potentially life-threatening bleeding inside the body.

When the body produces too many of these white blood cells, they can cause chronic inflammation leading to tissue damage. Sometimes, eosinophils can also move outside the bloodstream causing build-up and resulting inflammation in organs as well.

Likewise, vasculitis occurs when the immune system attacks the body’s blood vessels (arteries, veins and capillaries) by mistake. This can happen due to an infection, a medicine, or another disease or condition, according to the National Heart, Lung and Blood Institute.

When a blood vessel becomes inflamed, it can narrow, making blood flow difficult. It can close off completely, preventing blood from getting through altogether, or stretch and weaken resulting in a bulge called an aneurysm. If an aneurysm bursts, it can lead to serious, potentially life-threatening bleeding inside the body.

Symptoms of Vasculitis

Symptoms of vasculitis can vary depending on the organs affected and the severity of the condition. Usually, the most common symptoms include fever, swelling and a general feeling of illness, such as body aches and pains. Vasculitis can also cause fatigue, weakness and weight loss.

Vasculitis affecting the blood vessels in the skin can result in rashes, skin discoloration and ulcers (open sores with dead tissue). Rashes can cover large areas, causing blisters, purple-colored spots and patches on the skin, or hives that last longer than 24 hours. Skin sores mostly surface on the legs, buttocks or trunk of the body.

Other areas affected with accompanying symptoms include:
Muscle pain
Shortness of breath and cough
Congestive heart failure
Headaches, confusion, seizures, stroke, paralysis, numbness and lightheadedness
Kidney failure

Diagnosis and Treatment of Vasculitis

Blood tests or lab tests of other body fluids obtained from a patient with vasculitis generally indicates inflammation present in the body. Organ function tests can also be done depending on whether vasculitis is affecting a patient’s organs. A biopsy of affected tissue can provide a definitive diagnosis of the condition, while an angiogram, which is an X-ray of the blood vessels, can show a pattern of inflammation in the affected structures.

The primary goal of treatment is to stop the inflammation as well as suppress the immune system, the main catalyst of the disorder. Steroids or cortisone-related medicines, such as prednisone, are often used to reduce swelling, but aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) can also be prescribed.

When certain organs, such as the heart or lungs, are affected, other medical treatments may be needed to prevent further serious complications.

Treatment started early is often most effective. Remission (meaning the condition isn’t active) is possible with vasculitis, but it can also come back at any time. While rare, sometimes vasculitis does not respond to treatment, leading to permanent disability and even death.

A patient’s overall outlook depends on several factors, including:
  • Type of vasculitis
  • Organs affected
  • Progression of the disorder
  • Severity of the condition

Xolair’s Other Serious Side Effects and Complications

Xolair is linked to several other serious side effects including anaphylaxis, a severe, potentially life-threatening allergic reaction with a rapid onset, a combination of fever, joint pain and inflammation, and rash, parasitic infections, and elevated immunoglobulin E.

One study also found that Xolair may be associated with an increased risk of heart problems as well as complications involving the blood vessels in the brain. These problems and complications can include heart attacks, strokes, blood clots and a type of high blood pressure affecting the lungs’ arteries called pulmonary hypertension.

Fever, Joint Pain and Rash

Patients using Xolair post-FDA-approval, reported experiencing a combination of signs and symptoms including arthritis and joint pain, rash, fever and swollen lymph nodes. The symptoms typically appeared within one to five days after the first or subsequent injections of the medication. Some patients experienced a recurrence of symptoms after additional doses of the allergic asthma drug.

The drug’s label compared signs and symptoms of the condition to those seen in patients with serum sickness, a reaction to proteins in antiserum derived from a non-human animal source.

Parasitic (Helminth) Infections

In a one-year clinical trial that took place in Brazil, involving patients in the adult and adolescent populations at high risk for geohelminthic infections, such as roundworm, hookworm, whipworm and threadworm, over half (53 percent) of the patients taking Xolair experienced an infection compared to less than half (42 percent) of those taking a placebo (dummy pill). A standard stool examination was used to diagnose the presence of a parasitic infection.

The study’s findings indicated that a patient who had an infection was anywhere from .88 to 4.36 times more likely to have taken Xolair.

Please seek the advice of a medical professional before making health care decisions.

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Kristin Compton's background is in legal studies. She worked as a paralegal before joining Drugwatch as a writer and researcher. She was also a member of the National Association of Legal Assistants. A mother and longtime patient, she has firsthand experience of the harmful effects prescription drugs can have on women and their children. Some of her qualifications include:

  • Bachelor of Arts in Legal Studies | Pre-Law from University of West Florida
  • Past employment with The Health Law Firm and Kerrigan, Estess, Rankin, McLeod & Thompson LLC
  • Personal experience battling severe food allergies, asthma and high-risk pregnancies
Edited By

11 Cited Research Articles

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  2. DailyMed, NIH. (2017, June 15). Label: Xolair – omalizumab injection, solution. Retrieved from:
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  4. MedlinePlus, NIH. (2016, August 22). Malignancy. Retrieved from:
  5. MedlinePlus, NIH. (2017, February 13). Cancer. Retrieved from:
  6. MedlinePlus, NIH. (2017, March 29). Eosinophilic Disorders. Retrieved from:
  7. MedlinePlus, NIH. (2017, May 18). Cancer. Retrieved from:
  8. MedlinePlus, NIH. (2017, June 29). Vasculitis. Retrieved from:
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  10. National Heart, Lung, and Blood Institute, NIH. (2014, September 23). What Is Vasculitis? Retrieved from:
  11. Shiel, Jr., W. (2016, August 11). Vasculitis (Arteritis, Angiitis). Retrieved from:
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