Allergen Immunotherapy for Asthma: Shots vs. SLIT Tablets

When your asthma is triggered by pollen, dust mites, or pet dander, pills and inhalers might control symptoms-but they don’t fix the root problem. Allergen immunotherapy (AIT) does. It’s the only treatment that actually reprograms your immune system to stop overreacting to everyday allergens. And for people with allergic asthma, two forms are now widely used: allergy shots (subcutaneous immunotherapy, or SCIT) and SLIT tablets (sublingual immunotherapy). Both work. But which one’s right for you? The answer isn’t just about effectiveness-it’s about your life, your routine, and your long-term health.

How Allergen Immunotherapy Actually Works

Allergen immunotherapy isn’t a quick fix. It’s a multi-year course of controlled exposure. Think of it like training your body to stop seeing harmless things like dust mites as threats. Every dose, whether injected under the skin or held under the tongue, slowly teaches your immune system to tolerate the allergen instead of triggering asthma flare-ups.

This isn’t guesswork. The European Academy of Allergy and Clinical Immunology (EAACI) confirms AIT changes the disease course-not just masks symptoms. Studies show people on AIT use fewer asthma medications long-term, have fewer severe attacks, and even lower their risk of developing asthma if they started with just allergic rhinitis. Nine out of ten studies found kids and adults with allergic rhinitis who got AIT were far less likely to progress to asthma later on.

It only works if you’re allergic to something specific. You need a skin test or blood test to confirm your triggers. Dust mites, grass pollen, tree pollen-these are the best-studied allergens. If your asthma is caused by pollution, stress, or exercise, AIT won’t help. It’s not a cure-all. It’s a targeted tool.

Subcutaneous Immunotherapy: The Classic Shot

Allergy shots have been around since 1911. They’re the original form of immunotherapy. You get a small injection under the skin, usually in the upper arm. The process has two phases: build-up and maintenance.

During build-up, you go to the clinic once a week for 3 to 6 months. Each visit, the dose increases slightly. Then you switch to monthly shots for 3 to 5 years. That’s about 50+ visits total. It’s a big time commitment. You can’t skip a dose without resetting the schedule.

Why do people stick with it? Because for many, the results are worth it. Studies from the late 90s showed SCIT significantly improved both asthma and nasal symptoms. More recent real-world data from 14,614 patients found those on SCIT had fewer asthma attacks and used less medication-even 9 years after starting treatment.

But it’s not without downsides. You need to wait 30 minutes after every shot in case of a reaction. Rarely, people have a whole-body reaction-low blood pressure, trouble breathing. That’s why shots must be given in a medical setting. And if you miss a dose, you risk having to go back to a lower dose or even restarting the build-up phase.

Sublingual Immunotherapy: The Tablet Alternative

SLIT tablets are the newer, more convenient option. Instead of needles, you place a small tablet under your tongue and hold it there for 1 to 2 minutes before swallowing. It’s done at home-after the first dose, which is always supervised in a clinic.

There are FDA-approved tablets for grass pollen and ragweed, and in Europe, ACARIZAX is approved for house dust mite allergy-the most common trigger for year-round asthma. The standard dose is 6 SQ-HDM (Standardized Quality-House Dust Mite). Studies show this dose reduces inhaled steroid use by 42% on average, compared to just 15% with placebo.

SLIT is easier to fit into life. No weekly clinic trips. No needles. Just one tablet a day. Adherence rates are higher-75% to 80% of patients stick with it, compared to 60% to 65% for shots. That matters. Immunotherapy only works if you take it consistently for years.

Side effects? Usually mild. A tingling or itching under the tongue is common in the first few weeks. It fades. Rarely, there’s a systemic reaction-swelling, nausea, dizziness. That’s why the first dose is always given under medical supervision. But overall, SLIT is safer than shots when it comes to severe reactions.

Which One Works Better for Asthma?

Early studies, like the 1999 trial by Mungan, suggested SCIT was better for asthma control. SLIT helped nasal symptoms but didn’t improve asthma scores. That’s no longer the full picture.

Recent data from 2024 shows SLIT tablets for dust mites significantly reduce asthma exacerbations and corticosteroid use. In a real-world study of 2,688 patients, those on AIT had 20% fewer lower respiratory infections needing antibiotics after treatment ended. That’s a direct link between immunotherapy and fewer asthma-related hospital visits.

So which is more effective? The gap has narrowed. SCIT may still have a slight edge in symptom reduction for some. But SLIT matches it in preventing attacks and reducing medication use-with far fewer visits and a better safety profile.

Here’s the key: both work best for mild-to-moderate allergic asthma. If you’re on GINA Step 4 or 5 treatment (high-dose inhalers, oral steroids), AIT isn’t recommended yet. You need to stabilize your asthma first. AIT isn’t a rescue tool. It’s a long-term strategy.

Practical Differences: Time, Cost, and Lifestyle

Let’s compare what this looks like in real life.

• Time commitment: SCIT = 50+ clinic visits over 3 years. SLIT = 1 daily dose at home, plus one initial clinic visit.
• Convenience: SLIT wins. No scheduling conflicts, no travel, no needles.
• Cost: Shots may cost more upfront due to clinic visits, insurance copays, and time off work. SLIT tablets are expensive per dose, but no travel or time costs. Over 3 years, total costs can be similar.
• Adherence: SLIT has higher adherence. People are more likely to stick with something they do in their pajamas than drive across town every week.

One patient in Cardiff told me: "I used to cancel my shot appointments because of work. With the tablet, I forgot it once-and felt guilty for days. I didn’t want to risk losing progress." That’s the psychology of convenience.

Who Should Choose What?

There’s no one-size-fits-all. Here’s a simple guide:

• Choose SCIT if: You have multiple allergens (not just dust mites), live near an allergy clinic, prefer supervised dosing, or your doctor recommends it based on your specific test results. It’s also the only option in the U.S. for many allergens, since SLIT tablets are limited.
• Choose SLIT if: You’re allergic to dust mites or grass pollen, want to avoid needles, have a busy schedule, and can commit to daily dosing. It’s ideal for people who’ve struggled with adherence to daily inhalers.

Both require a confirmed allergy diagnosis. Neither works if your asthma is poorly controlled. And both need patience. You won’t feel better in weeks. It takes 6 to 12 months to notice changes. Full benefit? That’s after 2 to 3 years.

What Happens After Treatment Ends?

This is the biggest advantage of AIT over meds. When you stop shots or tablets after 3-5 years, the benefits often last. Many people stay symptom-free for years. Some never need to go back on inhalers.

A study tracking patients 9 years after starting AIT found reduced asthma medication use and fewer severe attacks-long after treatment ended. That’s disease modification. That’s the difference between managing asthma and changing its course.

That’s why experts call AIT the only treatment that can truly alter the natural history of allergic asthma. Other drugs keep you breathing. AIT helps you breathe easier-without them.

Barriers and Real-World Challenges

It’s not perfect. In the U.S., SLIT tablets for dust mites aren’t approved. You can get them via special import programs, but insurance rarely covers them. In Europe, they’re standard. That’s why adoption is higher there-60-70% of allergists offer SLIT, compared to 10-15% in the U.S.

Another hurdle: cost. AIT isn’t cheap. A year of SLIT can cost $1,000-$2,000 out-of-pocket. But when you factor in fewer ER visits, less steroid use, and fewer sick days, it pays for itself.

And then there’s the time. Three to five years is a long commitment. People quit. That’s why patient education matters. You need to know what to expect, why it takes so long, and how to track progress. Some clinics use apps to remind patients to take their tablet or log symptoms. Simple tools make a big difference.

What’s Next for Allergen Immunotherapy?

The field is evolving. Researchers are testing new formulations-adjuvants that boost immune tolerance faster, maybe cutting treatment time to 1-2 years. There’s also work on multi-allergen tablets, so one pill could cover dust mites, grass, and tree pollen.

Guidelines are catching up. EAACI is pushing for global standardization. The goal? Make AIT as routine as prescribing an inhaler. For mild-to-moderate allergic asthma, it should be the next step after inhalers fail-not the last resort.

One thing’s clear: the future of asthma care isn’t just more inhalers. It’s fixing the root cause. And for millions, that means choosing between a shot and a tablet.