SAFETY GUIDE
Is sublingual immunotherapy safe?
Side effects are common, but almost all are mild. Serious reactions can happen but are rare. No treatment for food allergy is risk-free, and neither is avoidance.
Mostly mouth itch
Rare serious reactions
Fewer reactions than OIT
Reviewed by Hunter Smith, MD · Last reviewed October 2026
0
epinephrine doses needed
for doses at home or in clinic, across 75,366 doses in the largest long-term peanut study (Kim 2019)
11×
fewer whole-body reactions
with SLIT than OIT in a head-to-head milk study (Keet 2012)
9 vs 43
doses in 100 cause a reaction
SLIT compared with OIT in a peanut study (Narisety 2015)
80 vs 28
children in 100 had mouth itching
on treatment compared with placebo, ages one to four (Kim 2024)
What usually happens
Mouth and throat first. Itching, tingling, sometimes mild swelling of the lips. Symptoms usually start within seconds of a dose and settle on their own in a few minutes.
Usually settles over the first weeks. Most families find the symptoms fade into something they stop noticing. Expect some, as a sign the immune system is recognizing the treatment.
Most patients have some. In one study, 45 of the 48 children had a symptom at some point. In a randomized trial of one- to four-year-olds, 80 in 100 on treatment had mouth itching, compared with 28 in 100 on placebo.
100 DOSES OF SLIT
About 5 in 100 doses caused a symptom, in the long-term study (Kim 2019)
What the serious risks are
Whole-body allergic reactions
Uncommon
Anaphylaxis is uncommon with SLIT. Across 75,366 doses taken at home and in clinic in the long-term peanut study, no one needed epinephrine. In a real-world group of 188 patients including higher-risk individuals, about 2 in 100 needed epinephrine at some point, and there were no life-threatening reactions.
Breathing in the liquid
Specific to liquid SLIT
In one study, two children breathed in the liquid instead of holding it under the tongue, and both needed epinephrine. Ask your allergist to show you exactly how to give a dose, and what to do if a child coughs or splutters during dosing.
Eosinophilic esophagitis
Watch for swallowing problems
The esophagus becomes inflamed, causing trouble swallowing, food getting stuck, or ongoing stomach pain. Reported with oral immunotherapy in about 3% of patients; much less common with SLIT, though SLIT studies are smaller. It can mean stopping treatment. Tell your allergist about any new swallowing problems.
How SLIT compares with oral immunotherapy
Far fewer serious reactions. In the milk study, whole-body reactions were about 11 times more common with OIT, breathing-related reactions about 9 times more common, and rescue medicine needed about 8 times more often.
But reactions of any kind are about the same. Roughly 29 in 100 SLIT doses and 23 in 100 OIT doses caused some symptom, including mild ones.
Epinephrine use is rare in SLIT. Multiple studies of peanut SLIT reported none used across all doses.
DOSES THAT CAUSED A REACTION, PEANUT STUDY (per 100 doses)
OIT43
SLIT9
Narisety 2015. Any reaction, including mild itch.
Who should be careful
Any form of immunotherapy can be riskier for some patients.
Poorly controlled asthma raises the risk of a serious reaction with any food immunotherapy.
A history of severe anaphylaxis is a common exclusion in food allergy trials, so there is less evidence about how safe immunotherapy is for this group.
Existing eosinophilic esophagitis may require extra caution, even with SLIT.
Everyone on food immunotherapy should continue to carry their epinephrine two-pack.
When to call your allergist
Symptoms that go beyond the mouth: hives elsewhere, stomach pain, vomiting, coughing, or trouble breathing.
Mouth symptoms that are getting worse rather than settling.
Ongoing trouble swallowing or food getting stuck.
Any reaction that needs epinephrine: use it first, get emergency help, then call your allergist later.
If your asthma is getting worse or you need your rescue inhaler often.
Missed doses, before deciding on your own whether to restart.
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