THE RESEARCH

What the research shows about sublingual immunotherapy for food allergy

About twenty years of studies

Mostly peanut

Not FDA-approved

Reviewed by Hunter Smith, MD · Last reviewed October 2026

Illustration of a woman placing a dose of sublingual immunotherapy liquid under her tongue at home

IN SHORT

Sublingual immunotherapy is often called SLIT. It means putting a small, measured amount of a food protein under the tongue every day.

Studies going back about twenty years show it can raise how much of a food a person with a food allergy can be exposed to before they react.

For most people it does not make the food allergy go away. Most people keep avoiding the food. What changes is how much of an accidental exposure it takes to cause a reaction.

Side effects are usually mild. The most common one is itching in the mouth or throat.

Most of the research is on peanut. There is much less on milk, egg, hazelnut and peach, and almost none on other foods.

SLIT is not approved by the FDA for food allergy. Allergists who offer it are prescribing it off-label.

It works less well than oral immunotherapy (OIT) at building up tolerance to a full serving. It causes fewer whole-body reactions.

Words you will see in these studies

Food allergy studies measure a few specific things. Knowing what they mean makes the studies easier to read.

Desensitized

you can be exposed to more of the food without reacting, as long as you keep taking the daily dose. The protection depends on staying on treatment.

Remission

protection that lasts after treatment stops. It is tested by pausing the dose for a set time and then doing a supervised challenge.

Oral food challenge

a supervised test in a clinic where you eat increasing amounts of the food while a medical team stands by. This is how studies measure whether treatment worked.

Milligrams (mg) of protein

doses are measured in milligrams (mg) of the food's protein, not in grams (weight) of food. One average peanut contains roughly 250 mg of peanut protein, so 750 mg is about three peanuts.

Intention-to-treat vs Per-Protocol

some study results count everyone who started the study whether they finished the study or not. This is called intention-to-treat. Other results only count the people who followed the study protocol without major deviations. This is called per-protocol. Both are given when studies report both.

HOW BIG IS A MILLIGRAM DOSE?

Chart comparing peanut protein amounts: 4 milligrams is the top sublingual immunotherapy dose, 300 milligrams equals one peanut, and 5,000 milligrams equals one full serving

What SLIT can do, depending on what you want from it

People choose SLIT to treat food allergy with different goals. The evidence is stronger for some goals than others. It is worth being clear about your goals before you start.

GOAL 1

Protection against an accidental exposure

67 in 100

This is what SLIT does best, and it is what most of the research measures. In the longest study, 67 out of 100 children could eat at least 750 mg of peanut protein (about three peanuts) after three to five years of daily dosing. That is not enough to eat peanut freely. It is usually enough that a bite of the wrong cookie is no longer an emergency.

GOAL 2

A gentler way to start treatment, or something to do while you wait

35 of 50

Some people use SLIT as a first step before oral immunotherapy. In one study of 188 patients, a small group went on to a low-dose challenge, and 35 of 50 of those challenged passed cleanly enough to start OIT at a 300 mg dose without the usual slow build-up. Note: That study followed patients up to the point of starting OIT. It did not report how they did afterward.

The wait lists for OIT can be long, buildup can take many in-clinic appointments, and a number of studies show that the younger a person begins treatment, the better their outcomes. SLIT may be something you can begin now because the observed visits are much shorter and the risk of severe reactions is very low.

GOAL 3

Lasting protection in very young children

48 in 100

In a randomized, placebo-controlled trial of 50 children aged 1 to 4, 48 out of 100 were still protected three months after stopping treatment, a state doctors call remission. None of the children on placebo reached remission. Results were best in the youngest children, aged one and two.

Three months is as long as anyone has tested, so nobody knows whether this protection lasts for years. A separate study that followed older children after stopping found that about half had lost their protection by around 22 weeks (about 6 months). Desensitization, and even remission, is not the same thing as a cure.

The studies on SLIT for food allergy

A plain-language summary of what each study found. The exact figures and journal citations are in the full data table further down.

Kim 2024

50 people

Peanut, ages 1–4

60 in 100 could eat about 4,400 mg of peanut protein after 3 years of SLIT, compared with none of the children on placebo. 48 in 100 were still protected 3 months after stopping.

What to know: Randomized and placebo-controlled. No child in either group needed epinephrine.

Kim 2023

54 people

Peanut, ages 1–11

About 70 in 100 who completed treatment could eat at least 800 mg. 36 in 100 passed a 5,000 mg challenge.

What to know: Open-label, no control group. Protection faded after stopping: half had lost it by about 22 weeks.

Kim 2019

48 people

Peanut, ages 1–11

67 in 100 could eat at least 750 mg — about 3 peanuts. 25 in 100 passed a 5,000 mg challenge.

What to know: 3 to 5 years of daily dosing. Just under a quarter of families stopped before the end.

Fleischer 2013

40 people

Peanut, ages 12–37

The average person who responded could eat about 496 mg — roughly 2 peanuts. No one could eat a full 5,000 mg serving.

What to know: The authors describe the effect as modest. One person had a reaction at home that needed epinephrine.

Narisety 2015

21 people

Peanut, ages 7–13

SLIT and OIT both raised thresholds, but OIT raised them far more — about 22× versus 141×.

What to know: 9% of SLIT doses caused any reaction, compared with 43% of OIT doses. No one on SLIT needed epinephrine.

Keet 2012

30 people

Milk, ages 6–17

1 of 10 who stayed on SLIT passed a full 8 g milk challenge, compared with 14 of 20 who moved on to OIT.

What to know: OIT caused about 11× more whole-body reactions. Two children needed epinephrine after breathing in the liquid.

Soller 2024

188 people

Several foods, ages 4–18

Among a small group who reached a test challenge, 35 of 50 passed the challenge and transitioned into a low OIT dose.

What to know: Over 19,000 doses, only one serious reaction during buildup. None during maintenance.

Williams 2025

305 people

Several foods

40 of 57 test challenges passed into a low OIT dose.

What to know: About 2 in 100 had a moderate reaction during buildup. No severe reactions.

Safety of SLIT

Safety is one of the biggest concerns about immunotherapy. This is what the research does and does not show.

Illustration of a patient describing mouth discomfort to an allergist, with a dropper bottle and syringe on the table

45 of 48

children had mild symptoms at some point, on about 5 in 100 doses (Kim 2019)

epinephrine for a home dose, across 75,366 doses (Kim 2019)

80 vs 28

in 100 children had mouth itching, on treatment versus placebo (Kim 2024)

Most reactions to SLIT for food allergy are mild and are limited to itching or tingling in the mouth and throat. Mouth itch is quite common. In one long study, 45 of 48 children had mild symptoms at some point, on about 5 in 100 doses.

Kim 2019

SLIT builds less tolerance than OIT.

Every study that compares SLIT with OIT has the same finding. If your goal is eating a full serving of the food, OIT is more likely to get you there.

Almost all the evidence is about peanut.

Milk and egg have essentially no published SLIT trials. The hazelnut evidence rests on 23 adults. Talk to your allergist about their internal data on SLIT for other foods.