Every treatment discussed for hay fever — antihistamines, nasal sprays, eye drops — has one thing in common: they treat the symptoms. Stop taking them, and the symptoms come back.
Allergen immunotherapy is different. It's the only treatment that works by retraining your immune system itself. For a significant proportion of people who complete a full course, the results last for years after treatment ends — and for some, they're permanent.
How does it work?
The principle is straightforward, even if the biology is complex. Immunotherapy involves giving your immune system repeated, controlled exposures to the allergen — in this case, pollen — in gradually increasing doses. Over time, this shifts the immune response away from the allergic reaction and towards tolerance.
Think of it like gradually habituating your nervous system to a loud noise. The first time, it startles you. By the hundredth time, it barely registers.
The two main forms
Subcutaneous immunotherapy (SCIT) — commonly called allergy shots — involves injections given at a clinic, usually weekly to start with, then monthly for a maintenance period. This has been used for over a century and has the largest body of clinical evidence behind it. In the UK, it's typically available through specialist NHS allergy clinics, though waiting lists can be long.
Sublingual immunotherapy (SLIT) — taken as drops or dissolvable tablets under the tongue — is a newer approach that can be done at home after an initial consultation. SLIT tablets for grass pollen allergy (brand names include Grazax and Pollinex) are licensed in the UK and available on the NHS, though availability varies by CCG.
SLIT tablets for grass pollen need to be started at least 16 weeks before the pollen season begins to reach their full effect. If you're thinking about starting treatment, speak to your GP in the autumn or winter — not when the season is already underway.
Who is it for?
Immunotherapy isn't for everyone, and it isn't a quick fix. A full course typically takes three years. The ideal candidate is someone whose hay fever is:
- Significantly impacting their quality of life — symptoms that aren't adequately controlled by antihistamines and nasal sprays
- Caused by a specific, identifiable allergen — grass pollen is the most common and the best-evidenced for SLIT
- Consistent year-on-year — if symptoms vary wildly, the picture may be more complex
It's not suitable for people with severe or unstable asthma, and it requires commitment to the full treatment course — stopping early reduces the long-term benefit significantly.
Pollen Level
Low (Post-Treatment)
Clinical trials show that a completed course of immunotherapy can reduce symptom scores by 30–40% compared to placebo — and for many patients, the effect continues to improve in the years after treatment ends.
The evidence
The evidence base for immunotherapy — particularly for grass pollen — is robust. Multiple large randomised controlled trials and Cochrane reviews confirm that both SCIT and SLIT reduce symptoms and medication use, and that effects persist after treatment ends. The National Institute for Health and Care Excellence (NICE) recommends sublingual immunotherapy tablets for severe grass pollen allergy in England.
How to access it
Start with your GP. If your hay fever is severe and not adequately controlled by standard treatments, you can be referred to an NHS allergy clinic for assessment. The specialist will confirm exactly which allergens are driving your symptoms (usually via skin-prick testing or blood tests) and advise whether immunotherapy is appropriate.
Privately, several companies now offer SLIT through online allergy services, making access faster than the NHS route — though costs vary considerably.
It's one of the few genuine long-term investments you can make in your health if hay fever is significantly affecting your life.