For people with asthma triggered by allergens like dust mites or pollen, standard inhalers and pills often only mask the problem. They don’t fix the root cause: your immune system overreacting to harmless substances. That’s where allergen immunotherapy comes in. Unlike medications that suppress symptoms, immunotherapy trains your body to stop seeing these triggers as threats. And for many, it’s the only treatment that can actually change the course of asthma long-term.
Two Ways to Train Your Immune System
There are two main types of allergen immunotherapy for asthma: subcutaneous immunotherapy (SCIT), better known as allergy shots, and sublingual immunotherapy (SLIT), delivered as tablets or drops under the tongue. Both work the same way-gradually exposing you to tiny, increasing amounts of the allergen-but they’re very different in how you get them.
Shots are given in a doctor’s office. You start with weekly injections for about 3 to 6 months, then switch to monthly shots for 3 to 5 years. That’s around 50 visits total. Each injection goes just under the skin, usually in the arm. It’s not painful, but it does mean planning your life around clinic appointments.
SLIT tablets, on the other hand, are taken at home. After your first dose is given under medical supervision (to watch for rare reactions), you swallow a tablet daily. The most common one for dust mite allergies is ACARIZAX, standardized to 6 SQ-HDM units. You hold it under your tongue for two minutes, then swallow. No needles. No trips to the clinic after the first visit.
Which One Works Better for Asthma?
Early studies, like the 1999 trial by Mungan, suggested shots were more effective for asthma symptoms, while SLIT mainly helped with runny noses. But that was over 20 years ago. Today’s evidence tells a different story.
A 2024 study tracking nearly 15,000 patients found that both SCIT and SLIT led to major drops in asthma medication use-especially inhaled corticosteroids. People on SLIT cut their daily steroid dose by an average of 42%, compared to just 15% for those on placebo. That’s not just symptom relief. That’s reducing your reliance on powerful drugs with side effects.
Another 2024 study of 2,688 patients showed that after stopping treatment, people who had SLIT had 20% fewer lower respiratory infections needing antibiotics. That’s huge. Fewer infections mean fewer asthma flare-ups, fewer ER visits, and fewer missed workdays.
Shots still have a slight edge in some studies for direct asthma symptom control, but the gap is closing. SLIT isn’t just a backup option anymore-it’s a proven, effective treatment for allergic asthma, especially when dust mites are the trigger.
Convenience vs. Commitment
If you hate needles and hate scheduling appointments, SLIT wins. Daily pills are easier to fit into a busy life. Studies show 75-80% of people stick with SLIT long-term. For shots, adherence drops to 60-65%. Why? Because life gets in the way. Miss a few shots, and the treatment loses momentum.
But SLIT isn’t perfect. The first few weeks can bring mouth itching, swelling, or an upset stomach. These usually fade within a month. You also need to remember to take it every single day. No pills for a week? You’re not getting the full benefit.
Shots come with their own risks. Rarely, they can trigger a serious whole-body reaction-anaphylaxis. That’s why you have to wait 30 minutes after each injection. But over time, the risk drops significantly. Most people tolerate shots well after the first few months.
Who Should Try It?
Immunotherapy isn’t for everyone. It only works if your asthma is truly allergy-driven. That means you need testing-skin prick tests or blood tests-to confirm you’re allergic to something like dust mites, grass, or tree pollen. If your asthma is triggered by cold air, smoke, or stress, immunotherapy won’t help.
You also need to have mild to moderate asthma. If you’re on high-dose steroids or have frequent severe attacks (GINA steps 4-5), immunotherapy isn’t recommended yet. You need to get your asthma under control first.
It’s also not a quick fix. You need to stick with it for at least 3 years. Some people see improvements in 6-12 months, but the real benefit-the lasting change-comes after treatment ends. Many people stay symptom-free for years, even without medication.
Cost and Access
In Canada and Europe, SLIT tablets are widely covered by insurance. ACARIZAX is approved and available. In the U.S., options are more limited, and coverage varies. Shots are usually covered, but the cost adds up with all those clinic visits.
Even if your plan doesn’t cover it, many patients find the long-term savings make it worth it. Less medication, fewer ER visits, fewer missed days at work or school. One study showed a 42% drop in steroid use-that’s hundreds of dollars saved per year.
Not all allergists offer SLIT. In Canada, it’s becoming more common, especially in major cities. If your doctor doesn’t offer it, ask if they can refer you to a clinic that does. You might need to travel a bit, but it’s often worth it for the convenience.
What About Kids?
Children with allergic rhinitis who get immunotherapy are less likely to develop asthma later. Nine out of ten studies show this protective effect. That’s why experts now recommend considering immunotherapy for kids as young as 5 with confirmed allergies and persistent symptoms.
SLIT tablets are approved for kids as young as 5 in Europe and Canada. The daily routine is easy for parents to manage, and kids usually tolerate it well. Shots are also safe for children but require more parental coordination.
The Bottom Line
Both allergy shots and SLIT tablets can change your asthma trajectory. They’re not just treatments-they’re investments in your long-term health. If you’re tired of relying on inhalers, want to reduce your medication, and have confirmed allergen triggers, immunotherapy is worth talking about.
Shots might be better if you want the strongest possible effect and don’t mind clinic visits. SLIT tablets are ideal if you value convenience, hate needles, and can commit to daily dosing. Neither is perfect. But both are better than just managing symptoms forever.
Ask your allergist for testing. If you’re allergic to dust mites or pollen, and your asthma isn’t fully controlled, immunotherapy could be the next step-not just another pill, but a real reset for your immune system.
Are allergy shots or SLIT tablets better for asthma?
Both are effective, but they work differently. Allergy shots (SCIT) have slightly stronger evidence for direct asthma symptom control, especially in older studies. SLIT tablets (sublingual immunotherapy) are equally effective at reducing medication use and asthma exacerbations, with better adherence because they’re taken at home. For most people with dust mite allergies, SLIT is now the preferred first choice due to convenience and safety.
How long does allergen immunotherapy take to work?
You might notice less sneezing or fewer inhaler uses within 6 to 12 months. But the real benefit-lasting improvement after stopping treatment-takes 3 to 5 years. That’s because immunotherapy works by retraining your immune system, not just masking symptoms. Skipping doses or stopping early reduces your chances of long-term success.
Can SLIT tablets treat all types of asthma?
No. SLIT only works for allergic asthma caused by specific triggers like dust mites, grass, or tree pollen. It won’t help if your asthma is triggered by cold air, exercise, smoke, or stress. You need allergy testing first to confirm the trigger. Also, it’s not recommended for severe, uncontrolled asthma (GINA steps 4-5).
Do I need to keep using my inhaler while on immunotherapy?
Yes-at first. Immunotherapy doesn’t work instantly. You’ll still need your rescue inhaler and possibly your daily controller medication. Over time, as your body adjusts, your doctor will help you reduce or stop these meds. Many patients end up on lower doses or none at all after 3-5 years.
Is SLIT safe for children?
Yes. SLIT tablets like ACARIZAX are approved for children as young as 5 in Canada and Europe. They’re well-tolerated, with mostly mild side effects like mouth itching. The biggest challenge is making sure kids take the tablet every day. For families, the long-term benefit-reducing asthma risk-is a strong reason to consider it.
What happens if I miss a dose of SLIT?
If you miss one day, just take your regular dose the next day. Don’t double up. If you miss more than a week, call your allergist. Missing doses for too long can reduce effectiveness and may require restarting the build-up phase. Consistency matters more than perfection-aim for 90% adherence.
Can I switch from shots to SLIT tablets?
Yes, but not automatically. If you’re already on shots and want to switch to SLIT, your allergist will need to start you on the tablet regimen from the beginning. You can’t just stop shots and pick up a tablet. The allergen dose and delivery method are different. Switching is common for convenience, but it requires a new treatment plan.
Is allergen immunotherapy covered by insurance in Canada?
In most provinces, SLIT tablets like ACARIZAX are covered under public or private drug plans, especially for dust mite allergies. Allergy shots are usually covered under provincial health plans as they’re administered in clinics. Check with your insurer or pharmacist-coverage varies by region and plan. Out-of-pocket costs can range from $100 to $400 per month, but long-term savings on asthma meds often offset this.
