It is expected that allergen preparations for sublingual immunotherapy (SLIT) will be approved in the United States shortly. Researchers examined SLIT experience in the United States, focusing on large, multicenter studies that will offer the proof of safety and efficacy required for approval. Large multicenter studies with both grass and short ragweed have been undertaken. The aggregate symptom medication score was improved 20–28% compared to placebo-treated persons in five single-season studies using sublingual grass pills, generally beginning 4 months before and continuing through the pollen season. Short ragweed pills, taken 4 months before and during the pollen season, lowered symptom/medication ratings by 24–26%. Short ragweed aqueous extract applied sublingually yielded similar effects. There has only been one tiny investigation with home dust mite and cat allergen extracts thus far. All of these investigations used a single allergen. One short trial comparing timothy alone versus timothy coupled with nine different pollen extracts raises unresolved issues about the efficiency of SLIT with diverse allergen mixtures.

SLIT is making its way to the United States. There will be allergy formulations that have been licensed and for which the optimal dose for effectiveness and safety has been determined. It would be improper to utilize the results from these major trials to support off-label usage of allergen extracts licensed for injectable or sublingual delivery of multiple allergen preparations.