Sublingual Immunotherapy (SLIT): What it is and How it Works

A useful overview from

Sublingual immunotherapy is a method of treating allergies by desensitizing individuals to allergens over time, in many cases with the goal that they be cured of their allergies. Sublingual immunotherapy (SLIT) is similar to subcutaneous immunotherapy (SCIT), commonly known as allergy shots. In principle, patients are given small doses of allergens in order to train the body not to react to them. Unlike allergy shots, SLIT, is a solution of allergen extracts, often called allergy drops, that is placed under the tongue.

The antigen in the solution interacts with the immune system to decrease the allergic individuals' sensitivity over time. Although the full course of treatment can last years, many patients report improvement in their symptoms after just a few months.

On a more scientific level, SLIT takes advantage of the tolerance of the oral mucosa, the mucous membrane of the mouth, to non-pathogenic antigens. When antigens are placed under the tongue, immune cells, called dendritic cells, move them to lymphoid tissues and an immune response occurs. By creating immune tolerance to these antigens, the process alters the allergic response.

One of the benefits of SLIT is that the sublingual mucosa, the membrane lining under the tongue, where the antigen is placed, has few pro-inflammatory cells, making an allergic reaction far less likely than when the allergen is encountered in the environment or even through injections. Early in treatment, sublingual dendritic cells secrete IL-10, which causes T-cells to inhibit the inflammatory response. Over time, sublingual immunotherapy decreases IgE production and the overall allergic response.

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First published in December 2009

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