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Grazax treatment for patients with severe seasonal allergic rhino conjunctivitis (hay fever)

Patient information A-Z

Grazax is a treatment for grass pollen allergic hay fever. It is used only for severe symptoms that have not responded to usual hay fever treatments. Grazax reduces allergic symptoms by giving you a regular fixed amount of grass pollen extract, allowing your immune system to build up a natural tolerance to grass pollen. This process is called de-sensitisation or immunotherapy.


Grazax is a tablet taken daily and dissolved under the tongue. For optimal effect Grazax should be started four months before the grass pollen season. Treatment should be continued all year round for a total of three years.

The first Grazax tablet will be administered in the hospital’s allergy clinic by a doctor or nurse. This is to ensure that the tablet is taken correctly, to monitor any side effects and give you the opportunity to discuss possible side effects with the doctor. Before taking the first tablet you will be asked to complete a consent form and have your pulse, blood pressure and peak expiratory flow rate checked.

One to two hours before taking Grazax you should have taken an antihistamine such as Cetirizine 10mg. The Grazax tablet should be carefully removed from the blister card, using dry fingers, and placed directly under the tongue. It will dissolve within seconds.

You should avoid swallowing for one minute and avoid food and drink for five minutes after taking the tablet. You will be asked to remain in the department for at least one hour under observation. On the second or third day after starting the medication you will be asked to phone or email the allergy department to report any side effects or symptoms. After that you will be reviewed annually by the allergy clinic at the end of the grass pollen season. Your GP (general practitioner) will continue to prescribe the medication and review you in the interim.

Side effects

The most common side effect of treatment with Grazax is itching and swelling of the mouth. These symptoms should be expected and are more common in the first few weeks of treatment. Therefore we advise you to take regular antihistamines during the first month of treatment to prevent these symptoms. Some patients also experience tiredness in the first few weeks. More serious reactions are less common but include swelling of the throat, generalised itchy rash, difficulty in breathing, abdominal pain and vomiting. If any of these symptoms occur you should seek medical help immediately.


Grazax should not be taken if you have cancer/ malignancy, severe asthma, severe inflammation of the mouth (for example cuts or sores) or an illness which affects the immune system. Grazax contains fish-derived gelatine and although there does not appear to be an increased risk of allergic reactions in patients with fish allergy, you should inform your allergy doctor.

Special care

Special care is required if you have had recent dental surgery, you have a severe allergy to fish or you have experienced severe allergic reactions to grass pollen immunotherapy injections previously. Please contact the allergy clinic for advice if any of these apply to you.

Vaccinations may be given without interrupting treatment with Grazax after medical evaluation of your general condition. Please inform the allergy clinic if you have any vaccinations planned.

Pregnancy and breast feeding

Treatment with Grazax should not be started during pregnancy because of the risk to the baby should a severe reaction occur. At present there is no experience for the use of Grazax during breast feeding. No effects on breast-fed infants are anticipated.

Help with this leaflet

If you have any questions regarding any aspect of your treatment, please do not hesitate to contact the allergy nurses on (01223) 348112.

Please email the allergy secretaries after you commence treatment:

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

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Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151