Sublingual immunotherapy (SLIT) is a common treatment for allergic rhinitis in Europe, and allergists in the United States are becoming increasingly interested in this form of therapy.
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August 2006However, several challenges need to be addressed before SLIT is readily available to the public, according to experts interviewed for this article.
For example, efficacy compared to subcutaneous immunotherapy (SCIT) and appropriate dosing need to be established, and a sublingual extract has yet to be approved by the Food and Drug Administration (FDA).
Despite these roadblocks, SLIT has the potential to help a number of patients with allergic rhinitis, including children and individuals who don’t want to undergo SCIT, according to experts.
“I think sublingual immunotherapy is going to fill an unmet need,” said Linda Cox, MD, an allergist in private practice at the Allergy and Asthma Center Ft. Lauderdale, Fla. and Chair of the American Academy of Allergy, Asthma and Immunology’s (AAAAI) Immunotherapy and Allergy Diagnostics Committee and the American College of Allergy, Asthma, and Immunology’s (ACAAI) Immunotherapy and Diagnostics Committee. She is also one of the authors of an AAAAI/ACAAI task-force report on the topic J Allergy Clin Immunol. 2006;117:1021–1035).
Investigating the Efficacy of SLIT
To help determine whether SLIT is a viable option for patients, the AAAAI/ACAAI task force conducted a meta-analysis of 47 SLIT studies.
“Every one isn’t positive, but it’s very clear that in majority of cases there is a clinical benefit,” said one of the analysis authors Harold Nelson, MD, Professor of Medicine at the National Jewish Medical and Research Center in Denver, Colo.
SLIT may be effective in patients because the oral cavity is an immunologically privileged site, said Samuele E. Burastero, MD, of the San Raffaele Scientific Institute in Milan, Italy, and author of a SLIT data review that found the therapy to be highly efficacious (Curr Opin Otolaryngol Head Neck Surg. 2006;14:197–201).
Data indicate dendritic cells in the oral mucosa, encountering antigen in the absence of “danger” signals, activate a prevalently regulatory, rather than Th2 (pro-allergic) immune response, explained Dr. Burastero. Recirculation of allergen-specific T regulatory lymphocytes to target organs of allergic inflammation can explain the clinically significant improvement of allergies affecting the upper respiratory tract, he said.
Side Effects
SLIT is not without side effects, said Dr. Nelson. They generally include local itching and swelling under the tongue and on the lips. Occasional gastrointestinal side effects will occur, but not with any great regularity, he said. There have been a few reports of wheezing or breaking out in hives, but no anaphylactic reactions or near fatal reactions have been reported.