Allergen immunotherapy (desensitisation) for grass-pollen hay fever
Grass pollen extract
An allergen treatment that gradually trains the immune system to react less to grass pollen in severe hay fever.
What is Grass pollen extract?
Grass pollen extract is a specialist allergy treatment, a form of immunotherapy or desensitisation, used for people with severe grass-pollen hay fever that is not controlled by usual medicines. It contains a carefully prepared amount of grass pollen that is given regularly, often as a tablet or drops under the tongue or sometimes as injections, to gradually train the immune system to react less. The most important thing to know is that, because it deliberately exposes you to your allergen, it can cause allergic reactions, including, rarely, a serious whole-body reaction (anaphylaxis), so the first dose is often given where you can be watched. It is taken over several years to give lasting benefit.
Education and reference only. This is a plain-language guide to Grass pollen extract — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Grass pollen extract is used for allergen immunotherapy, also called desensitisation, in people whose grass-pollen hay fever (allergic rhinitis) is severe and not well controlled by antihistamines and steroid nasal sprays. It contains a measured, standardised preparation of grass pollen, the very thing the person is allergic to, given in a controlled way so the immune system slowly learns to tolerate it. It may be given as a tablet or drops placed under the tongue, or as a course of injections, depending on the product. It is started and supervised by a specialist allergy service and is a long-term treatment.
How it works
In hay fever, the immune system overreacts to grass pollen and releases chemicals that cause sneezing, a runny or blocked nose and itchy, watery eyes. Allergen immunotherapy works by giving the body small, controlled exposures to grass pollen over time, which gradually shifts the immune response towards tolerance, so the same pollen triggers a much weaker reaction. Because the immune system changes slowly, the treatment is given regularly over several years, and the benefit can continue after the course is finished. Since it works by deliberate exposure to the allergen, the same process that gives benefit is also what can occasionally trigger an allergic reaction.
Company & origin
Originated / developed by: Specialist manufacturers.
A specialist allergy treatment used in the UK to desensitise people with severe grass-pollen hay fever, given as under-the-tongue tablets or drops, or as injections.
What it treats
Conditions Grass pollen extract is used for
Practical use
How to take Grass pollen extract
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it exactly as your specialist directs; for under-the-tongue products, hold the tablet or drops under the tongue as instructed before swallowing.
- Expect to have the first dose given in a clinic where you can be watched for a reaction.
- Keep taking it regularly over the full course, often around three years, as stopping early can lose the benefit.
- Tell your specialist about any mouth itching or swelling, and seek urgent help for breathing difficulty, widespread rash or faintness.
- Start and continue it as advised in relation to the pollen season, and do not change the schedule yourself.
Weighing it up
Advantages & disadvantages of Grass pollen extract
Advantages
- Can give lasting relief from severe grass-pollen hay fever, sometimes continuing after the course ends.
- Treats the underlying allergy rather than just masking symptoms, unlike everyday hay-fever medicines.
- Under-the-tongue tablets or drops can often be taken at home after the supervised first dose.
Disadvantages
- Can cause allergic reactions, including, rarely, a serious whole-body reaction (anaphylaxis).
- Commonly causes itching or swelling in the mouth or throat, especially early on.
- Needs to be taken regularly over several years to work properly.
Practical use
Good to know
The key point with grass pollen extract is that it works by deliberately exposing you to your allergen, so an allergic reaction is the main thing to be aware of. Mild reactions are common, especially with under-the-tongue products, including itching, tingling or swelling in the mouth, throat or lips, which usually settle as treatment continues. More rarely, a serious whole-body reaction (anaphylaxis) can happen, which is why the first dose is often given in a clinic where you can be watched, and why injection courses are given by trained staff. It is a long-term commitment, usually taken over about three years and started before or at the beginning of the pollen season, and stopping early can mean the benefit is lost. It is reserved for severe hay fever that ordinary treatments have not controlled, and your specialist will explain what to do if you feel unwell after a dose.
Who should not take it / use with caution
- People who have had a serious allergic reaction to the extract or its ingredients should not use it.
- It is used with great caution, or avoided, in people with severe or poorly controlled asthma.
- It should only be started and supervised by a specialist allergy service.
Monitoring
- Watching for an allergic reaction after the first dose and after changes to treatment.
- Reviewing how well hay-fever symptoms are controlled over each season.
- Checking asthma is well controlled before and during treatment.
Side effects
- Itching, tingling or swelling in the mouth, lips or throat, especially with under-the-tongue products.
- A flare of hay-fever-type symptoms such as sneezing, itchy eyes or a runny nose after a dose.
- Rarely, a serious whole-body allergic reaction (anaphylaxis), which needs emergency treatment.
Key interactions
- It is used with caution alongside medicines for severe asthma, as poorly controlled asthma raises the risk of reactions.
- Certain blood-pressure medicines can affect how an allergic reaction is treated, so tell your specialist what you take.
- Give a full medicines list, as your specialist needs to know about anything affecting your allergy or its treatment.
Available as: Tablets or drops placed under the tongue, or a solution for injection, depending on the product.
Answers
Grass pollen extract: frequently asked questions
What is grass pollen extract used for?
It is used for allergen immunotherapy, or desensitisation, in people with severe grass-pollen hay fever that is not controlled by usual medicines, to train the immune system to react less.
Why is the first dose given in a clinic?
Because the treatment deliberately exposes you to your allergen, it can occasionally cause a serious reaction, so the first dose is often supervised where help is available.
How long do I have to take it?
It is a long-term treatment, usually taken over about three years; stopping early can mean the lasting benefit is lost.
What reactions should I expect?
Mild itching, tingling or swelling in the mouth or throat is common, especially with under-the-tongue products, and usually settles; serious reactions are rare but need urgent help.
Will it cure my hay fever?
It can give long-lasting relief that may continue after the course ends, but it works gradually and is reserved for severe hay fever that other treatments have not controlled.
Authoritative sources
- BNF
- NICE CKS
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