Sublingual immunotherapy

Recent claims have been made that sublingual immunotherapy (SLIT) may be a viable alternative to injection immunotherapy (SIT). Animal studies show that when allergens are administered topically, they are handled differently, and IgE responses can be reduced. Most published studies of human SLIT have been small but show fairly consistent benefits on symptom scores, with few systemic side effects. Objective measures of allergen reactivity usually do not change. Relatively few subjects have been treated in SLIT trials compared with the numbers that would be required to validate new drug therapies. On the plus side, SLIT appears to work in adults and in children; it offers some logistic advantages and seems to be safe. Giving allergen by mouth rather than by injection should decrease the costs of immunotherapy, but the cumulative dose of allergen used in SLIT has been between 20 to 375 times the dose given in conventional SIT. Further cost-benefit analysis is needed. On the other hand, standard SIT is effective and is supported by better clinical and experimental evidence. The balance sheet for SLIT is improving, but on the current evidence, SLIT requires further evaluation before it could be recommended for use in routine clinical practice.