Sublingual immunotherapy (SLIT) is an alternative way to treat allergies without injections (subcutaneous immunotherapy, SCIT). Small doses of the allergens are placed under the tongue and gradually the dosages are increased until a patient develops tolerance. Currently the only forms of SLIT that are FDA approved in the United States are Grass Pollen and Ragweed that are available. Dust Mite tablets should be available soon.
Although allergists are able to prescribe sublingual immunotherapy for patients as an off label indication for those patients who do not want to do allergy shots. An important question for those who do sublingual immunotherapy is, what is the minimal effective duration of treatment? Currently for SCIT, it is recommended that patients undergo treatment for 3-5 years. For SCIT, a previous study showed that three years of SLIT induces sustained tolerance for at least 2 years after treatment has stopped. A recent study published in JAMA, tested the efficacy of 2 years of daily SLIT with grass pollen allergen compared to 34 subjects who received placebo. Additionally, 36 subjects received monthly subcutaneous immunotherapy without sublingual immunotherapy. One year after stopping treatment, efficacy was tested by using the Total Nasal Symptom Score at 0 to 10 hours after a nasal allergen challenge. Both treatments were effective compared to placebo at year 2, there was not a statistically significant improvement in total nasal symptom scores in patients treated with SLIT compared to placebo at year 3. Similarly, SCIT did not show efficacy compared to placebo at year 3 after stopping treatment for 1 year. These results show that 2 years of SLIT duration is not enough for long term clinical benefit and support the practice of clinical practice of maintaing SLIT for a longer period of time.
Overall. both SCIT and SLIT were effective, but two years treatment was insufficient for long-term tolerance.