Allergen Immunotherapy for Asthma: Shots vs. SLIT Tablets

For people with asthma triggered by allergens like dust mites or pollen, taking inhalers every day isn’t always enough. You might still wake up wheezing, need rescue inhalers more than you’d like, or feel like your asthma is controlling your life-not the other way around. That’s where allergen immunotherapy comes in. It’s not another inhaler. It’s not a quick fix. It’s the only treatment that actually changes how your immune system reacts to allergens over time. And right now, you have two main choices: allergy shots (SCIT) or sublingual tablets (SLIT). Both aim to retrain your body’s overreaction to things like dust, pollen, or pet dander. But which one works better for your asthma? And which one will actually fit into your life?

How Allergen Immunotherapy Works

Allergen immunotherapy doesn’t mask symptoms. It rewires your immune system. Think of it like training a nervous dog. Every time you’re exposed to dust mites, your body screams "danger!" and releases histamine, causing coughing, wheezing, and tightness in your chest. Immunotherapy slowly introduces tiny, controlled amounts of the allergen-either under your skin or under your tongue-so your body learns it’s not a threat. Over months and years, your immune system stops overreacting. The result? Fewer flare-ups, less reliance on steroids, and sometimes, long-term relief even after you stop treatment.

This isn’t theory. Nine out of ten studies show kids and adults with allergic rhinitis who get immunotherapy are far less likely to develop asthma later. For those already living with asthma, real-world data from over 14,000 patients shows a sustained drop in asthma medication use over nine years. That’s not just symptom relief. That’s disease modification.

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 starts with weekly shots during a build-up phase-lasting three to six months-then moves to monthly maintenance shots for three to five years. That’s about 50 visits over the full course. You need to stay in the clinic for 30 minutes after each shot because, while rare, serious reactions like anaphylaxis can happen.

It’s inconvenient, yes. But it’s also powerful. Older studies, like the 1999 trial by Mungan, showed allergy shots significantly improved both asthma and rhinitis symptoms in people sensitive to dust mites. Even today, many allergists still consider SCIT the gold standard for asthma control, especially when multiple allergens are involved. It’s flexible: you can mix several allergens in one shot. If you’re allergic to both grass and dust mites, you don’t need two separate treatments.

But the cost isn’t just financial. It’s time. Missing a shot means falling behind. Travel, work, holidays-all disrupt the schedule. And if you’re already struggling with asthma symptoms, adding frequent clinic visits can feel overwhelming.

SLIT Tablets: The Daily Alternative

Sublingual immunotherapy (SLIT) is simpler in theory: a tablet you hold under your tongue for one to two minutes, then swallow. No needles. No clinic visits after the first dose. Once your allergist confirms you can tolerate the first tablet safely, you take it at home every day.

The most common SLIT tablet for asthma triggered by house dust mites is ACARIZAX, standardized to 6 SQ-HDM units. Studies show patients on this dose cut their inhaled corticosteroid use by an average of 42%-compared to just 15% in placebo groups. That’s a huge win. Fewer steroids mean fewer side effects like weight gain, mood swings, or bone thinning.

And adherence? Higher. About 75-80% of people stick with SLIT daily, compared to 60-65% for shots. Why? Convenience. No scheduling. No waiting rooms. You take it while brushing your teeth or having breakfast.

But it’s not perfect. The tablet only works for one allergen at a time. If you’re allergic to both grass and dust mites, you’d need two different tablets-maybe one for spring, one for year-round. And while SLIT is safer than shots, you can still get reactions: mouth itching, swelling, stomach upset. These usually fade after a few weeks, but the first dose must be given under medical supervision.

Which One Works Better for Asthma?

Here’s the truth: both work. But they work differently.

For pure asthma symptom control, older data suggested shots were slightly more effective. But that was before modern, standardized SLIT tablets became widely available. Recent real-world studies, like the 2024 analysis by Asperti, show SLIT is just as good at reducing asthma exacerbations and steroid use. In fact, SLIT users had a 20% drop in lower respiratory infections needing antibiotics after treatment ended-something shots didn’t show as clearly.

So why does the myth that shots are "better" still exist? Because shots have been studied longer. But the tide is turning. SLIT isn’t just a backup option anymore. For people with dust mite-triggered asthma-especially those who live in humid places like Manchester-it’s now a first-line choice.

Who Should Choose Shots?

Allergy shots are still the best option if:

• You’re allergic to multiple allergens (e.g., pollen, dust mites, cat dander) and want one treatment that covers them all.
• You’ve tried SLIT and didn’t respond well.
• You have moderate to severe asthma and want the most aggressive disease-modifying option available.
• You’re comfortable with regular clinic visits and don’t mind needles.

It’s also the only option if you’re under 18 and need treatment for tree pollen allergies-because no SLIT tablet for trees is approved in the UK yet.

Who Should Choose SLIT Tablets?

SLIT tablets are ideal if:

• Your asthma is mainly triggered by house dust mites (the most common indoor allergen in the UK).
• You hate needles or can’t make regular clinic visits.
• You want to reduce your steroid inhaler use-and the side effects that come with it.
• You’re disciplined enough to take a pill every day, even when you’re tired or busy.

It’s also a strong choice for adults who’ve tried inhalers and nasal sprays but still wake up gasping for air.

What If Neither Works?

Immunotherapy isn’t magic. It doesn’t work for everyone. And it won’t help if your asthma is triggered by things like cold air, exercise, or pollution-not allergens. If you’re on GINA Step 4 or 5 treatment (high-dose steroids plus other controllers), immunotherapy isn’t recommended yet. Your asthma needs to be stable first.

Also, you must know what you’re allergic to. Skin prick tests or blood tests (specific IgE) are required before starting. If you’re allergic to mold but take a dust mite tablet? It won’t help. You need the right match.

Cost, Access, and the Real World

In the UK, SLIT tablets are licensed and available on the NHS, but access varies. Not every GP can prescribe them-you’ll need to be referred to an allergy specialist. Some areas have long waiting lists. Shots are more widely available but still require specialist care.

Cost-wise, SLIT tablets can be expensive without insurance. But if you’re cutting your steroid inhaler use by 40%, you’re saving money long-term. Fewer emergency visits, fewer sick days, fewer antibiotics-that adds up.

And while the US lags behind Europe in SLIT adoption, the UK is catching up. More allergists here now offer SLIT. It’s no longer a niche option.

What to Expect Over Time

Neither treatment gives results overnight. You’ll need patience. Most people start noticing fewer symptoms after 6-12 months. Full benefit takes 2-3 years. And you must finish the full 3-5 year course. Stopping early means losing the long-term protection.

Side effects are usually mild. For shots: redness, swelling at the injection site. For SLIT: itchy mouth, throat irritation, stomach upset. These fade with time. Serious reactions are rare-especially with SLIT.

After treatment ends, many people stay symptom-free for years. Some never need asthma meds again. Others need less. But the biggest win? You’re not just managing asthma-you’re changing its course.

Final Decision: It’s About Your Life

There’s no single right answer. It’s about your lifestyle, your allergens, and your goals.

If you’re the type who remembers to take your daily vitamin, hates needles, and wants to cut back on steroids? SLIT tablets are likely your best bet.

If you’re allergic to multiple things, want the strongest possible effect, and don’t mind clinic visits? Shots still have their place.

Both are better than just living with asthma. Both are proven to reduce your risk of severe flare-ups. Both are the only treatments that change your immune system-not just your symptoms.

Ask your allergist: "Which option gives me the best shot at living without asthma controlling me?" Then choose the one that fits your life.