The extracts used in SLIT are the same FDA approved, standardized, extracts used in injection immunotherapy. However, because the FDA has not yet approved these allergy extracts for sublingual administration, they are classified as “off-label”. Off-label use of an FDA approved product is extremely common in the United States, and is often utilized by physicians. The classic example is the off-label use of aspirin to help prevent heart attacks, which occurred for years when the FDA had not yet approved this use, even though it was widely known that aspirin treatment was safe and effective.

There is frequently a very long lag time between when a medical treatment is proven to be effective and when the FDA approves it to treat a specific medical condition.  However, because of this, insurances usually will not cover sublingual immunotherapy.