Allergy shots can reduce symptoms of asthma, use of inhaled medications, and allergy-related asthma attacks, according to a review of studies published in The Cochrane Library. The reviewers, however, warn that the treatment can also cause systematic side effects that range from a stuffy nose to fatal anaphylactic shock.
The review found that about 30% of asthma patients experience improved breathing after receiving a series of injections—known as allergen immunotherapy—that desensitize their immune systems to specific irritants. The number of patients experiencing systematic reactions of any severity nears 20%, although the reviewers note that more than 8% of patients receiving placebo experience similar reactions. Fatalities remain rare at one death per 2.5 million injections.
Immunotherapy is most risky for patients with poorly controlled asthma. Allergists should review each patient’s symptoms before every injection, according to Harold Nelson, MD, of National Jewish Health in Denver. “Patients shouldn’t be actively wheezing, they shouldn’t be waking up at night due to asthma symptoms and their pulmonary function should be relatively normal,” said Nelson. If symptoms are flaring up, doctors should postpone the injection.
The review encompasses 88 studies, with 13 published since 2001, and about 3,800 participants. All the studies were randomized controlled trials. Most of the studies focused on house mite or pollen allergies, while a few looked at animal dander, mold, latex, or a combination of allergens.
“Among allergists there’s no question that asthma caused by allergies is responsive to immunotherapy,” said Nelson. “The advantage of immunotherapy is that it causes long-lasting, if not permanent, improvement.”
Furthermore, most people who have allergy-induced asthma also have nasal symptoms, added Nelson. “They have to inhale steroids into their lungs and spray them into their nose, and a lot of people don’t like to do that forever. Immunotherapy treats both the nasal and chest symptoms.”