A new class of medications called Immunoglobulin E (IgE) inhibitors is available to treat allergy-related asthma. Omalizumab (Xolair) was the first approved therapy to target the IgE molecule.

It is normal for your airways to tighten and become inflamed if you inhale a dangerous substance. This reaction is an attempt by your body to prevent the threat from traveling too far into your lungs. The airways open up again when the threat has passed.

If you have allergy-induced asthma, however, your airways are overly responsive to mild substances called allergens. Your body's response to these triggers leads to blocked airways and the symptoms of asthma.

Most asthma drugs relieve symptoms by simply "blunting" the response to an asthma trigger. In contrast, IgE blockers actually prevent the response from occurring in the first place.

To understand this more fully, it helps to know what makes something an asthma trigger. If you have an allergy to a substance like pollen, mold, or dust mites (all called allergens), your body makes too many IgE antibodies to that substance. These antibodies recognize and fight against the individual allergens. But, having too many of the IgE antibodies can make the body too responsive to these allergens, and lead to an allergic reaction like asthma.

Xolair binds to excess IgE antibodies in your bloodstream. This stops the IgE antibodies from recognizing the asthma-provoking allergens. In other words, omalizumab stops the body from overreacting to asthma triggers by making the IgE antibodies ineffective. This interrupts the excessive inflammatory response even before it starts. Xolair is given by injection every 2 - 4 weeks to prevent asthma flare-ups. Xolair was approved by the FDA in 2003 for patients ages 12 and older with moderate-or severe persistent asthma. The most common side effect is an injection-site rash.

IgE inhibitors also holds promise for the treatment of other forms of allergic disease.

Note: In February 2007, the Food and Drug Administration requested the manufacturers of omalizumab (Xolair) to include a “boxed warning” emphasizing that this medicine may cause a severe and life-threatening allergic reaction (anaphylaxis). Omalizumab is approved for patients who have moderate-to-severe asthma related to allergies and whose symptoms are not controlled by inhaled corticosteroids. It is given by injection in a doctor’s office every 2 - 4 weeks.

The warning indicates that patients may develop anaphylaxis after any dose of omalizumab, even if they had no reaction to the initial shot. Health care providers need to observe patients carefully for 2 hours after they receive an omalizumab injection. However, because an allergic reaction can occur up to 24 hours after the injection, patients need to know the signs and symptoms of anaphylaxis and how to self-administer emergency treatment. Symptoms may include:

• Trouble breathing
• Chest tightness
• Dizziness
• Fainting
• Itching and hives
• Swelling of the mouth and throat