By Darin Ingels, ND

People who suffer from allergies and asthma now have a viable alternative to conventional injection immunotherapy in treating their symptoms. Although injection immunotherapy has been the gold standard for allergy desensitization for almost 100 years, over 300 published studies shows that sublingual immunotherapy (SLIT) is equally or more effective than allergy shots in reducing allergy and asthma symptoms. The allergy extracts used in SLIT are identical to those used in injection immunotherapy, but rather than receiving a shot on a weekly or monthly basis, oral drops are administered under the tongue, often on a daily basis.

Recent research shows that during SLIT, the allergen is absorbed into the oral mucosa. The underlying dendritic cells, which express high-affinity IgE receptors, produce IL-10 and TGF- β and upregulate indoleamine dioxygenase, a cytosolic enzyme that suppresses T-helper cell responses. This leads to a decrease in immunoglobulin E (IgE) and a reduction in recruitment and activation of proinflammatory cells in the target tissue. This mechanism of action is similar to that observed in conventional immunotherapy.

Although SLIT seems relatively new in the United States, it has been used clinically for more than three decades. Its use has increased steadily in the past 15 years, but mostly in other countries, especially those in Europe. Some critics of SLIT have argued that there is a lack of research documenting its efficacy. However, two recent meta-analyses showed that SLIT significantly reduced symptoms of allergic rhinitis and asthma, as well as decreased use of rescue medication. Studies show SLIT effectively treats allergies to pollen, mold, dust mites, animal dander, foods and latex. A 3-year study found SLIT plus allergy medication led to significant reductions in allergy symptom scores and airway hyperreactivity by 73% and 61%, respectively, while no improvement was observed in the group taking allergy medications only. Other shorter studies suggest SLIT can start to reduce allergy symptoms and asthma within weeks to months.

There are many advantages to SLIT over injection immunotherapy. SLIT may be used in
patients who failed to respond to injection immunotherapy or had an anaphylactic reaction to their injection. There are no reports of SLIT causing anaphylaxis, making it a safer alternative to injections. SLIT is more convenient than injection immunotherapy, since the drops are administered at home by the patient, meaning fewer office visits and no needles. This is ideal for children and others who may have a fear of needles. There are no significant medical disadvantages of SLIT treatment; however, many insurance companies in the United States do not reimburse for SLIT, which may be financially limiting for some individuals.

Myself and other physicians have successfully treated thousands of patients with allergies and asthma with SLIT and have not observed any significant side effects or severe reactions to the treatment. Although injection immunotherapy can take a year or longer to begin controlling allergies or asthma, SLIT will often diminish symptoms within weeks. Like any treatment, not everyone responds to SLIT and some patients do feel better with allergy injections. Nonetheless,
SLIT is a safe, effective treatment that should be considered as a first line therapy for the treatment of allergies and asthma.