The Safety of Sublingual Immunotherapy (SLIT) — Including for Children

AllergyRhino
2 days ago
3 min read

Short Answer:

Sublingual immunotherapy (SLIT) is a clinically proven, safe, and well-tolerated treatment for hay fever and environmental allergies. It’s suitable for adults and children aged five and above, with only mild, short-lived side effects like slight mouth itching. Severe allergic reactions are extremely rare.

When people first hear about allergy immunotherapy, one of the most common questions is:

“Is it safe?”

This is especially important for parents thinking about treatment for their child’s hay fever. The reassuring answer is yes — the most widely used form today, sublingual immunotherapy (SLIT), has an excellent safety profile for both adults and children.

From Injections to Tablets: A Century of Progress

Immunotherapy isn’t new. It’s been used for over 100 years. Originally, the allergen (such as pollen extract) was injected under the skin. While effective, those injections could sometimes trigger serious allergic reactions, so they had to be given in hospital or clinic settings.

In the UK, this led to a gradual shift away from injections.

Over the past 20–30 years, treatment has evolved to the much safer sublingual form, taken as a daily tablet or spray under the tongue. The allergen is absorbed safely through the mouth, retraining the immune system without the risks that injections once carried.

Why SLIT Is So Much Safer

SLIT has a dramatically lower risk of severe reaction compared to injection immunotherapy.

The most common side effects are mild and local — such as itchiness, tingling, or slight swelling under the tongue that lasts only a few minutes after taking the dose.

For a small number of people, these effects can feel irritating at first. In those cases, specialists often recommend a short course of antihistamines until the body adjusts. For most patients, the symptoms settle quickly and treatment continues smoothly.

As Professor Adam Fox explains:

“The nice thing about sublingual immunotherapy is it’s dramatically safer, and severe allergic reactions are extremely rare.”

Safe and Effective for Children

One of the most encouraging aspects of SLIT is that it’s licensed for use in children from age five.

For families, this means a safe, non-invasive treatment option that can significantly reduce hay fever symptoms and improve quality of life.

Hay fever in children can cause poor sleep, loss of concentration, and reduced school performance, especially during exam season. With SLIT, parents can be confident that they’re choosing a clinically proven, long-term solution that helps their child feel and function better.

Many AllergyRhino families tell us that treatment has not only reduced sneezing and eye-watering but also helped their child “finally sleep through the night” during pollen season.

The Bottom Line

Sublingual immunotherapy is one of the safest, most effective long-term treatments for hay fever and other environmental allergies.

Severe allergic reactions: extremely rare
Typical side effects: mild, short-lived mouth itch or tingling
Suitable for: adults and children aged 5+

For most people, SLIT offers a well-tolerated and proven way to tackle the root cause of allergy — without the risks once linked to injection immunotherapy.