Sublingual Immunotherapy (SLIT)

What is this sublingual immunotherapy?

Sublingual immunotherapy (SLIT) is an allergy treatment that works by dissolving tablets or liquid under your tongue every day. It exposes you to small amounts of your allergen in a controlled way until you don’t have an allergic reaction to it anymore (or you have fewer symptoms of an allergic reaction).

When the tablet or liquid dissolves under your tongue, the allergen enters your bloodstream through mucous membranes in your mouth. Once in your blood, special immune cells (T-cells) recognize it. Over time, instead of triggering an immune reaction, the T-cells send signals to your immune system that calm it down. With regular treatment, this helps prevent you from getting symptoms like sneezing, itchy eyes and a runny nose.

Healthcare providers most commonly use SLIT to treat people who have allergic reactions to pollen and other airborne particles (“hay fever” or allergic rhinitis). This might include grasses, weeds and dust mites. But they’re also starting to use it to treat food allergies, like peanuts.

How does sublingual immunotherapy work?

When you start sublingual immunotherapy, your healthcare provider (usually an allergist) will give you your first dose at their office. There, they can monitor you for reactions and show you how to take SLIT at home. Your provider will give you tablets (or liquid) to use at home and instructions on how to use them. They’ll also prescribe a self-injectable epinephrine device (like Epipen® or Auvi-Q®) in case you have an allergic reaction (this is rare).

For some allergens, you might have a period of dose escalation, or updosing. This means you get a little more allergen per dose over time (a few weeks to a few months) until you reach full strength. You might have to go to your provider’s office for each dose escalation.

You’ll have to take SLIT at home every day. Follow your provider’s instructions exactly. An example of how they might direct you to take your dose might be:

• Put the tablet or a specific number of drops under your tongue. Let the tablet dissolve.
• Wait one to two minutes before swallowing.
• Wait five to 15 minutes (sometimes longer) before eating or drinking.

Who can use sublingual immunotherapy?

Sublingual immunotherapy tablets are usually best for people who have one allergen that causes most of their symptoms. You need to be able to stick to a schedule of taking them as directed, every day.

SLIT isn’t recommended if you have:

• Severe or hard-to-manage asthma.
• Eosinophilic esophagitis.
• A sensitivity or allergy to the inactive ingredients (ingredients that aren’t the allergy you’re treating).
• A history of severe reactions to SLIT.

Your provider will perform allergy skin tests or blood tests before starting SLIT.

What are the advantages of sublingual immunotherapy?

Advantages of SLIT include:

• Effectiveness (compared to over-the-counter treatments). Studies suggest SLIT works as well or better than at-home and over-the-counter allergy treatments, like antihistamines or nasal sprays. If taken regularly for several years, they can provide symptom relief for a few years after stopping treatment.
• Comfort. SLIT provides an alternative to allergy injections for people who don’t like shots.
• Convenience. You can use SLIT at home most of the time without having to go into your provider’s office for every treatment.
• Safety. SLIT is less likely to cause severe reactions than allergy shots.
• Reduction of asthma symptoms. Studies suggest SLIT can reduce asthma symptoms in some people.

What are the risks of SLIT?

There are some drawbacks to SLIT, including:

• Effectiveness (compared to shots). SLIT might be slightly less effective than allergy shots.
• Consistency. You need to take your tablets or drops consistently every day for SLIT to work.
• Limitations on tablets. In the U.S., the Food and Drug Administration (FDA) has only approved tablets for a few allergens. You can also only treat one allergy at a time with tablets.
• Side effects. SLIT can cause mild side effects or, rarely, severe complications.

Side effects and complications

Side effects and complications of SLIT include:

• Itchy mouth, throat or ears. This is the most common side effect. It usually goes away shortly after taking your dose of SLIT.
• Swelling in your mouth or throat.
• Anaphylaxis, a severe allergic reaction. This is rare.
• Eosinophilic esophagitis. This is inflammation of your esophagus that can develop over time. It’s a rare complication of SLIT.

How long does sublingual immunotherapy take to work?

Sublingual immunotherapy doesn’t work right away. It can take a few months to build a tolerance to airborne allergens. You may need to take SLIT daily for years to get the full benefit.

Ideally, you’ll start taking SLIT for seasonal allergies (like grass and ragweed) 12 weeks before the allergy season starts. You’ll continue SLIT through your allergy season to prevent symptoms, the same way you’d take daily allergy medicines. You usually have to take SLIT for dust mite allergies year-round.

Some studies show that if you take SLIT daily for three years or more without breaks, it’ll keep working to reduce your allergy symptoms for at least two years after you stop taking it.

How well does sublingual immunotherapy work for allergies?

Depending on what kind of allergies you’re treating, studies suggest that SLIT can reduce your symptoms by at least 40% compared to over-the-counter allergy treatments.

When should I call my healthcare provider?

Contact your provider if you have any questions about how to take SLIT or what kinds of reactions to look out for. Helpful questions to ask include:

• How do I take it?
• When do I take it?
• What should I do if I miss a dose?
• What kinds of reactions should I look out for?
• What should I do if I have a serious reaction?
• Are there any activities or medications I should avoid while taking SLIT?
• When should I follow up with you?

Which is better, allergy shots or sublingual immunotherapy?

Some people prefer SLIT to allergy shots (and vice versa) for many reasons. Your provider can give you guidance on which they think would be better for your specific situation. Which treatment they recommend could depend on:

• Whether you want to — and are able to — do daily treatments at home (SLIT) or less frequent shots (usually weekly or every other week) at your provider’s office.
• What kind of allergies you have.
• If you need to treat multiple allergies at once.

Is sublingual immunotherapy FDA-approved?

Yes, the U.S. Food and Drug Administration (FDA) has approved certain SLIT tablets. Extracts for many more allergens are FDA-approved for use in allergy shots.

Approved SLIT tablets

FDA-approved SLIT tablets include those for treating:

• Dust mites.
• Some grasses, including Timothy.
• Ragweed.

In other parts of the world, like Canada and Europe, tablets for certain tree allergens are approved.