Allergy immunotherapy: the evidence, and what the guidelines actually say

Not for the off-label liquid form. The 2017 joint AAAAI/ACAAI focused practice parameter on sublingual immunotherapy did not endorse off-label use of aqueous SLIT drops, on the basis that no aqueous sublingual formulations are FDA-approved and there are no direct comparisons between a tablet and an aqueous extract of the same allergen. The parameter does support allergen immunotherapy as a treatment class, including the FDA-approved sublingual tablets. Anyone reading about allergy drops should know this position exists rather than hear only the favourable half.

Four tablets, all for allergic rhinitis: Oralair (a five-grass mixture), Grastek (Timothy grass), Ragwitek (ragweed), and Odactra (house dust mite). Each treats a single allergen source — or, in Oralair’s case, one defined grass mixture. There is no FDA-approved liquid or multi-allergen sublingual product, which is why customized drops are prescribed off-label.

No, but it does mean something specific. Off-label prescribing is legal and routine in US medicine, and the allergen extracts used are FDA-regulated. What it means here is that the FDA has not evaluated that particular customized mixture, and that professional guidelines have not endorsed the aqueous format. Both things are true at once, and an honest answer states both.

A Cochrane review of 60 randomized, placebo-controlled trials found sublingual immunotherapy reduced allergic-rhinitis symptoms and medication use compared with placebo. That body of evidence is why the treatment class is accepted. It does not resolve the separate question of dosing equivalence between tablets and customized liquid extracts, which remains unsettled.

The most relevant addition is real-world outcome data on the aqueous, telemedicine-delivered route the 2017 parameter had little evidence about. A 2026 retrospective cohort of 2,897 patients reported clinically meaningful improvement rising from 28% at 12 months to 45% at 24 months, adherence above 90%, and no cases of anaphylaxis. It is observational — it describes what happened to those patients and does not establish equivalence with tablets or superiority over in-person care.

If your allergy is to a single source covered by an approved tablet, the FDA-approved route exists and is worth discussing with a clinician. If you are sensitized to several allergens, no approved tablet covers that combination, and the practical choice is between in-clinic injections and off-label customized drops — with the guideline position and the real-world data both on the table. Anyone with a history of anaphylaxis, poorly controlled or severe asthma, or suspected food or drug allergy should be evaluated in person regardless.