When your asthma won’t stay under control no matter how many inhalers you use, it’s time to ask: is this really about asthma-or is it about allergies? Many people with asthma don’t realize their symptoms are driven by allergens like house dust mites, pollen, or pet dander. And while inhalers calm the flare-ups, they don’t fix the root cause. That’s where allergen immunotherapy comes in-the only treatment that actually changes how your immune system reacts to allergens over time.

What Is Allergen Immunotherapy?

Allergen immunotherapy (AIT) is a long-term treatment that trains your immune system to stop overreacting to harmless substances like dust mites or grass pollen. Instead of just masking symptoms with steroids or antihistamines, AIT slowly exposes you to tiny, controlled amounts of the allergen. Over months and years, your body learns not to see it as a threat. This isn’t theory-it’s backed by decades of research. Studies show people who complete AIT often need fewer asthma medications, have fewer flare-ups, and even reduce their risk of developing full-blown asthma if they started with just allergic rhinitis.

There are two main ways to do this: allergy shots (subcutaneous immunotherapy or SCIT) and SLIT tablets (sublingual immunotherapy). Both work on the same principle, but how you get the treatment couldn’t be more different.

Allergy Shots: The Classic Approach

Subcutaneous immunotherapy, or allergy shots, has been around since 1911. You get a small injection under the skin, usually in the upper arm. The process has two phases: build-up and maintenance.

During the build-up phase, you go to the clinic once a week for about 3 to 6 months. Each visit, your dose increases slightly. Then, you move to maintenance-once a month for 3 to 5 years. That’s roughly 50+ visits total. It’s a big time commitment. But it’s also been the gold standard for decades.

Studies show SCIT works well for asthma triggered by dust mites, grass, and tree pollen. One 1999 study found it improved both nasal and asthma symptoms in mite-sensitive patients. More recent real-world data from a study of over 14,000 people showed those on SCIT had significantly fewer asthma exacerbations and used less medication over 9 years.

The downside? You have to be monitored for 30 minutes after each shot because of the small risk of a serious allergic reaction-like anaphylaxis. That’s why you can’t do this at home. It also means taking time off work, arranging childcare, or dealing with clinic wait times. For many, that’s a dealbreaker.

SLIT Tablets: The Daily Alternative

Sublingual immunotherapy (SLIT) is simpler in concept: you put a tablet under your tongue and hold it there for 1 to 2 minutes before swallowing. No needles. No clinic visits after the first dose.

For dust mite allergies, the tablet ACARIZAX delivers 6 SQ-HDM (Standardized Quality-House Dust Mite). You take it daily, year-round. The first dose is always given in a medical setting because of the rare but possible risk of throat swelling or low blood pressure. After that, you can do it at home-before breakfast, while brushing your teeth, whatever fits your routine.

Recent studies show SLIT tablets work just as well as shots for asthma caused by dust mites. One 2024 trial found patients on SLIT reduced their daily inhaled corticosteroid dose by 42%, compared to just 15% for placebo. That’s not just symptom relief-it’s a real reduction in medication burden. And it’s not just about inhalers: another study of nearly 2,700 patients showed a 20% drop in lower respiratory infections needing antibiotics after AIT ended.

Adherence is higher with SLIT. Around 75-80% of people stick with it daily, compared to 60-65% for shots. Why? Convenience. No appointments. No needles. Just a small tablet and a daily habit.

How Do They Compare?

Here’s the real question: which one is better for you?

So which is better? It depends on your life.

If you’re someone who can schedule regular appointments, doesn’t mind needles, and wants the most proven track record-shots are solid. But if you hate clinics, travel often, or just want to manage your treatment between coffee and your morning emails-SLIT tablets win.

Who Should Avoid Both?

Neither option works for everyone. Both require that your asthma is triggered by a specific, identifiable allergen. If your symptoms come from smoke, cold air, exercise, or stress-AIT won’t help.

Also, if you’re on GINA Step 4 or 5 treatment (high-dose steroids, biologics, or frequent oral steroids), AIT isn’t recommended. Your asthma is too unstable. First, get it under control with medication. Then consider immunotherapy as a next step.

And you need testing. Skin prick tests or blood tests for specific IgE are required before starting. You can’t guess your allergens. A dust mite tablet won’t help if you’re allergic to ragweed.

Real-World Results: What Patients Actually Experience

Patients who stick with AIT for the full 3-5 years often say the same thing: "I didn’t realize how much I was relying on my inhaler until I didn’t need it anymore."

One woman in Bristol, 42, with dust mite asthma, switched from daily steroid inhalers to SLIT tablets after two years of poor control. "I was using my blue inhaler 3-4 times a week. After 18 months on ACARIZAX, I went from that to maybe once a month. And I haven’t had a chest infection in over two years."

Others say the initial throat itching from SLIT was annoying-but faded after a few weeks. Some found the daily routine easy to forget. Setting phone reminders helped. For shots, the biggest complaint wasn’t the pain-it was the time. "I missed three months once because of work travel. My allergist said I had to restart the build-up phase. That felt unfair."

Cost is another factor. In the UK, SLIT tablets are often covered by the NHS if you meet criteria. Shots may require private payment unless you’re in a specialist clinic. In the US, access is more limited-only about 10-15% of allergists offer SLIT, compared to 60-70% in Europe.

What’s Next for Allergen Immunotherapy?

The field is evolving fast. New formulations are being tested with adjuvants-additives that make the immune system respond more strongly, potentially shortening treatment time. Some researchers are looking at multi-allergen tablets, so one dose could cover dust mites and grass pollen together.

There’s also growing evidence that starting AIT early in children with allergic rhinitis can prevent asthma from developing. One review of nine studies found kids who got immunotherapy were 80% less likely to develop asthma later. That’s huge.

But the biggest barrier isn’t science-it’s awareness. Many GPs still don’t know AIT is an option. Patients often go years without being tested for allergies. If you’re on multiple asthma meds and still struggling, ask your doctor: "Could this be allergy-driven? Could immunotherapy help?"

Is It Worth It?

Yes-if you’re ready to commit.

Allergen immunotherapy isn’t a quick fix. It takes years. You won’t feel better overnight. But if your asthma is tied to allergens, and you’re tired of managing symptoms instead of fixing the problem, this is the closest thing to a cure we have.

SLIT tablets offer freedom. Shots offer tradition. Both work. The best choice isn’t about which is stronger-it’s about which fits your life.

Next Steps: What to Do Now

If you’ve been struggling with asthma despite using inhalers, here’s what to do next:

1. Ask your GP or asthma nurse for a referral to an allergist.
2. Get tested for specific allergens-skin prick or blood test for IgE.
3. If dust mites or grass pollen are triggers, ask about SLIT tablets or shots.
4. Compare your lifestyle: Can you commit to monthly clinic visits? Or do you prefer daily tablets at home?
5. Discuss costs and NHS eligibility-some SLIT tablets are funded in the UK for eligible patients.

This isn’t about choosing between two treatments. It’s about choosing the right path to finally take control-not just of your symptoms, but of your life.