Canadian FAIT ResearchWhat is SLIT?
Sublingual immunotherapy, usually shortened to SLIT, is a food allergy treatment where a small, carefully measured liquid dose of an allergen is placed under the tongue, held there for one to two minutes, and then swallowed or spit out, depending on the protocol an allergist prescribes. It's given daily, at home, after the starting dose has been introduced and observed in a clinical setting.
The idea behind SLIT is exposure therapy: repeated, tiny doses of the allergen are believed to interact with immune cells in the lining of the mouth in a way that can help the immune system become less reactive to that food over time. This is sometimes called building tolerance or raising the reaction threshold — it is different from a cure, and different from being able to eat the food freely without any risk.
SLIT has been studied for a number of common food allergens, including peanut, tree nuts, cow's milk, and egg, and researchers continue to study its safety and effectiveness in clinical trials and hospital-based allergy programs.
How it works, step by step
- Allergy testing and evaluation. Your allergist confirms the specific allergy and discusses whether SLIT is a reasonable option for your child's situation.
- First dose, in clinic. The very first, smallest dose is given under medical supervision so your care team can watch for any reaction.
- Build-up (escalation) phase. Over a period of weeks to months, the dose is gradually and carefully increased under your allergist's direction, with regular check-ins.
- Maintenance phase. Once a steady daily dose is reached, it's continued at home, typically for as long as your allergist recommends.
- Ongoing monitoring. Regular follow-up appointments track how your child is responding and whether the plan needs adjusting.
Because doses are small, SLIT is generally associated with mild, local reactions — such as itching or tingling in the mouth — more often than the whole-body reactions sometimes seen with other approaches. That said, any allergen immunotherapy carries some risk of reaction, which is why it's only started and adjusted under an allergist's care.
Who may benefit
SLIT isn't the right fit for every child or every allergy, and only your allergist can assess your child's specific case. In general, families and clinicians sometimes discuss SLIT for children who:
- Have a confirmed IgE-mediated food allergy that's been evaluated by a specialist
- Are looking for a gentler starting point, sometimes because a higher-risk food or a more reactive history makes oral immunotherapy feel like a bigger first step
- Want to explore treatment gradually, with smaller doses than oral immunotherapy typically uses
- Are able to attend regular follow-up appointments and do consistent at-home dosing
Some allergy programs also use a short course of SLIT as a bridge before moving into oral immunotherapy for higher-risk allergies — another reason this is a conversation to have directly with your child's allergist, not a decision to make from a website.
Questions to bring to your allergist
- Is SLIT a reasonable option for my child's specific allergy and history?
- What would the build-up schedule and appointment commitment look like for us?
- What reactions should we watch for at home, and what's our emergency plan?
- How long would maintenance dosing likely continue?
- How does SLIT compare to oral immunotherapy for our child's situation?
- Is this treatment currently available to us here in BC, and through which allergy clinic or program?
Related reading: Oral Immunotherapy (OIT), Future Research, and our FAQ.