Allergies are caused by an overreaction of the immune system to innocuous substances or allergens, such as pollens, house dust mites, animal dander or venom allergen from insect stings (bees or wasps). Allergen immunotherapy works by suppressing the body's reaction to allergies. 

Types of immunotheraphy

Allergen immunotherapy is usually given by injections under the skin (subcutaneous immunotherapy). The injections are given weekly at the hospital for 2-3 months, followed by every 4-6 weeks for three years.

You can also take tablets which dissolve under the tongue (sublingual immunotherapy) for grass pollen allergy. The first dose of oral treatment needs to be taken under observation in the hospital followed by daily treatment at home. 

Side effects

Both treatments may some side effects, such as itchiness and swelling. Serious reactions, such as difficulty in breathing, faintness or sickness (anaphylaxis), are rare (approximately once in every 1,000 injections and even less often with tablets) and mostly occur within 30 minutes of the dose. A 60-minute observation period after each injection is obligatory.  


Most people respond very well to treatment with a reduction of symptoms and medication use. Not every allergic patient may be suitable for allergen immunotherapy and individual assessment is therefore crucial. 

Treatment is mainly given for allergic rhinoconjunctivitis (including severe hay fever), and for life-threatening reactions to insect stings. Symptomatic treatment may still be required and patients with insect allergies should continue carrying an adrenaline injector device. 

Find out more about our asthma and allergy services

Sometimes severe allergic reactions can occur so it is important to know how to avoid contact with latex if you have this allergy.

Anaphylaxis is a serious allergic reaction that can be life-threatening or fatal.

People with hay fever (rhinitis) have inflamed lining in their nose, which causes it to be blocked, running and itchy, as well as causing sneezing.

Urticaria is a condition which involves the development of itchy wheals (hives) on the skin.

Around 5–10% of people who have a problem with a drug are suffering from a drug allergy, possibly one prescribed by their GP or as part of an investigation in hospital. 

Between 1-10% of adults and children in the UK have a food allergy.

The Trust offers a wide range of allergy services for adults of all ages. This includes specialist services for patients with difficult to manage allergies.

Allergy team contact information


Fulham wing/South block, Fulham Road

Tel: 020 7351 8892
Fax: 020 7351 8949