Sublingual Immunotherapy is method of allergy treatment that uses an allergen solution given under the tongue, which over the course of treatment, reduces sensitivity to allergens. Sublingual immunotherapy, or SLIT, has a very good safety profile and is given at home in adults and children.

As more patients are treated with SLIT, additional side effects are being studied. A serious anaphylactic reaction occurred in a patient being treated with multiple allergens prepared from commercially available US extracts.

The basis of sublingual immunotherapy is treatment of the underlying allergic sensitivity. Allergic symptoms improve as the allergic sensitivity improves. As a safe and effective method of treating the underlying disease, sublingual immunotherapy is capable of modifying the natural progression of allergic disease which can begin with allergic food sensitivities and eczema in young children and progress through allergic rhinitis and asthma in older children and adults.Fact: date=January 2007

A recent study, published in Allergy 2007: 62: 943–948, showed that a 3-year course of Sub-cutaneous immunotherapy had long-term clinical effects, by significantly reducing the development of asthma in children with allergic rhinoconjunctivitis up to 7 years after treatment. In a recent review of ALL studies on SLIT by the American Academy of Allergy, Asthma and Immunology published in Journal of Allergy and Clinical Immunology, 2007: 6: 1466-1468, 35% of studies resulted in significant reductions in medications and symptom scores but 38% of studies found no significant benefit from SLIT. When SLIT did work, it was typically less effective than with conventional subcutaneous injection immunotherapy and sometimes SLIT took two years to show significant clinical benefit.

Mechanism

Sublingual immunotherapy is taken as drops 3 times/day or tablets, placed under the tongue, containing a specific allergen which interacts with the immune system to decrease allergic sensitivity. Commonly the medication is taken once a day. The antigen persists on the mucosal surface and is taken up by dendritic cells which interact with T lymphocytes (T-cells).

Sublingual immunotherapy takes advantage of immunologic tolerance of the oral mucosa to non-pathogenic antigens such as foods and resident bacteria. Consider the vast number of antigens we are exposed to every day which do not elicit an allergic response. Dendritic cells in the oral mucosa act as antigen presenting cells (APC) to T-cells in the cervical lymph nodes. This system modulates the allergic response by creating immune tolerance to antigens. The sublingual mucosa has few pro-inflammatory cells, such as mast cells, which would provoke an allergic reaction. This explains in part the safety margin of sublingual therapy.

Early in treatment, sublingual dendritic cells secrete interleukin 10 (IL-10) which induces regulatory T cells to inhibit the inflammatory response. Long term changes that occur with immunotherapy include a decrease in mast cell sensitivity and a decrease in IgE production by B-cells. With sublingual immunotherapy there is a decrease in the IgE/IgG4 and a decrease in the TH1/TH2 ratio.