Allergen Immunotherapy for Asthma: Shots vs. SLIT Tablets Explained

What Is Allergen Immunotherapy for Asthma?

Most asthma treatments-like inhalers and steroids-just calm down symptoms. But if your asthma is triggered by allergens like dust mites or pollen, there’s a treatment that actually changes how your body reacts to them. It’s called allergen immunotherapy (AIT). Unlike pills or sprays that mask symptoms, AIT trains your immune system to stop overreacting to things like dust, pollen, or pet dander. Over time, this can reduce how often you wheeze, cough, or need your rescue inhaler.

There are two main ways to do this: allergy shots (subcutaneous immunotherapy, or SCIT) and SLIT tablets (sublingual immunotherapy). Both work by slowly exposing you to tiny, controlled amounts of the allergen you’re sensitive to. The goal? To build tolerance so your body no longer sees it as a threat.

It’s not a quick fix. You need to stick with it for 3 to 5 years. But for many people, the payoff is real: fewer flare-ups, less medication, and sometimes even stopping asthma from getting worse.

How Allergy Shots (SCIT) Work

Allergy shots have been around since 1911. They’re injections given under the skin, usually in the upper arm. The process has two phases.

First, the build-up phase: you get a shot once a week for about 3 to 6 months. Each shot has a slightly higher dose of the allergen. This part requires frequent visits to your allergist’s office.

Then comes the maintenance phase: you switch to one shot every 4 to 6 weeks. You’ll keep this up for 3 to 5 years. Most people need around 50 visits total over that time.

Why go through all this? Because studies show SCIT works well for asthma triggered by dust mites, grass, or tree pollen. One 1999 study found it significantly improved both nasal and asthma symptoms in people sensitive to house dust mites. More recent real-world data from 2024 confirms it reduces asthma exacerbations and cuts down on steroid use over the long term.

But it’s not perfect. You have to show up. Miss a few appointments, and the treatment loses momentum. And while most reactions are mild-redness or swelling at the injection site-there’s a small risk of a serious allergic reaction. That’s why you’re asked to wait 30 minutes after each shot.

How SLIT Tablets Work

SLIT tablets are a newer option. Instead of needles, you place a small tablet under your tongue and hold it there for about 2 minutes before swallowing. It’s painless. No needles. No clinic visits after the first dose.

The first dose is always given in a doctor’s office because there’s a small chance of a reaction. After that, you take it daily at home. That’s the big advantage: you don’t need to rearrange your life for weekly shots.

The most common SLIT tablet for asthma is ACARIZAX, which targets house dust mites. It’s standardized to 6 SQ-HDM units. In a 2024 study, people using this tablet reduced their daily inhaled steroid dose by an average of 42%-compared to just 15% in the placebo group. That’s not just a symptom change. It’s a medication reduction.

SLIT also cuts down on infections. One study of nearly 2,700 patients showed a 20% drop in lower respiratory infections needing antibiotics after treatment. That’s huge for people who get sick every time their asthma flares.

Side effects? Usually mild: an itchy mouth or throat. That fades after a few weeks. Systemic reactions are rare-much rarer than with shots.

Shots vs. Tablets: Which Is More Effective?

For decades, allergy shots were the gold standard. But newer studies are changing that.

Early research, like the 1999 Mungan study, showed SCIT improved asthma symptoms while SLIT mainly helped with nasal stuffiness. That made shots seem better for asthma.

But those studies were small and short. Today’s evidence tells a different story.

A 2024 analysis of over 14,600 patients found that both SCIT and SLIT led to big, lasting drops in asthma and allergy medication use. Over 9 years, people on either treatment needed fewer inhalers, fewer oral steroids, and had fewer emergency visits.

For dust mite asthma specifically, SLIT tablets now match or even beat shots in reducing steroid use. And because people stick with SLIT more often-75% to 80% adherence versus 60% to 65% for shots-the real-world results are often better.

So, is one more effective? Not clearly. Both work. But SLIT might give you better results simply because more people actually take it.

Convenience, Safety, and Daily Life

Let’s be honest: most people choose based on lifestyle, not just science.

If you’re the type who hates needles, hates clinics, or has a busy schedule, SLIT tablets win. You take it while brushing your teeth. No appointment. No waiting room. No travel.

Shots require planning. You need to block off time every week for months. That’s hard if you work shifts, have kids, or live far from an allergist.

Safety matters too. With shots, there’s a small but real risk of anaphylaxis. That’s why clinics require you to wait after each injection. With SLIT, severe reactions are extremely rare. Most side effects are local and temporary.

But SLIT isn’t for everyone. You have to be disciplined. If you forget a dose for a week, you don’t get the full benefit. Shots are more forgiving-if you miss one, your doctor can just adjust the next dose.

Who Should Try It? Who Should Avoid It?

AIT isn’t a cure-all. It only works if your asthma is allergic. If your triggers are cold air, exercise, or pollution, it won’t help.

You need a clear diagnosis first. Skin prick tests or blood tests for specific IgE antibodies will confirm if dust mites, grass, or pollen are your main triggers.

AIT is best for mild to moderate asthma (GINA steps 1-3). If you’re on high-dose steroids or use your rescue inhaler daily, you’re likely too unstable to start. Your doctor will want to get your asthma under control first.

Also, AIT only works for specific allergens. You can’t treat all allergies at once. Most SLIT tablets target just one: dust mites or grass. Shots can be customized for multiple allergens, but that increases complexity and cost.

Children can benefit too. Studies show AIT can prevent asthma from developing in kids with allergic rhinitis. That’s why some pediatric allergists now recommend it earlier.

Cost, Access, and Insurance

Cost varies wildly depending on where you live.

In Europe, SLIT tablets are widely covered by public health systems. In Australia and the U.S., coverage is patchy. Some private insurers pay for it. Others don’t. You might need to pay out-of-pocket-up to $1,500 to $3,000 per year.

But think long-term. If SLIT cuts your steroid use by 40%, you save money on inhalers, doctor visits, and missed work. One study showed a 20% drop in antibiotic use for respiratory infections. That’s fewer prescriptions, fewer ER trips.

Access is another hurdle. In the U.S., only 10-15% of allergists offer SLIT tablets. In Europe, it’s 60-70%. In Australia, availability is growing but still limited outside major cities. You may need to travel to a specialist clinic.

Shots are more widely available but require more frequent visits. If you live in a rural area, that’s a big barrier.

What Happens After You Stop?

This is the biggest reason to consider AIT.

Most asthma medications only work while you’re taking them. Stop the inhaler? Symptoms come back.

AIT is different. After 3 to 5 years, you stop. But the benefits often last for years-even decades.

Studies show people who complete AIT have fewer asthma attacks 5, 10, even 15 years later. Their lungs stay more stable. They need fewer medications. Some stop needing inhalers entirely.

It’s the only asthma treatment that can change the disease’s natural course. That’s why experts call it the only disease-modifying therapy for allergic asthma.

Real-Life Choices: Who Wins?

So, shots or tablets?

If you’re allergic to dust mites and live near a specialist clinic, SLIT tablets are the smart choice. Less hassle. Fewer side effects. Just as effective. And you can take it while watching TV.

If you’re allergic to multiple things-like pollen, mold, and cat dander-and you can commit to weekly visits, shots give you more flexibility in allergen mix.

If you’re a parent with a child who has allergic rhinitis and you’re worried about asthma developing, AIT-especially SLIT-is worth discussing now. Prevention is easier than treatment.

If you’re on high-dose steroids or have uncontrolled asthma, wait. Get your symptoms under control first. Then talk to your allergist about whether AIT is right for you.

What’s Next for Allergen Immunotherapy?

The field is evolving fast. New tablets for more allergens are in development. Researchers are testing adjuvants-additives that make the treatment work faster or stronger. Some trials are looking at 2-year protocols instead of 5.

There’s also a push to standardize practices globally. Right now, Europe leads in guidelines and access. The U.S. and Australia are catching up, but slowly.

One thing’s clear: AIT is no longer a niche option. It’s becoming a core part of asthma care for allergic patients.

For many, it’s not just about breathing better today. It’s about not needing to breathe better tomorrow.