What is allergen immunotherapy and how does it work?

Allergies such as hay fever, dust mite allergy, and allergic asthma affect millions of people across the UK and can significantly impact daily life. While many patients rely on antihistamines or nasal sprays to control symptoms, these treatments do not address the underlying cause of allergy.

In this article, consultant allergist Dr Stephanie Kayode explains what allergen immunotherapy is, how it works, and who may benefit from this long-term treatment option.

What is allergen immunotherapy?

Allergen immunotherapy is a medical treatment designed to reduce a patient’s sensitivity to specific allergens such as pollen, house dust mites, animal dander, or insect venom.

Rather than simply treating symptoms, immunotherapy gradually trains the immune system to become less reactive to substances that trigger allergic reactions. Over time, this can lead to lasting improvements in symptoms and may even alter the natural course of allergic disease.

It is recommended for people with:

• Allergic rhinitis (hay fever).
• Dust mite allergy.
• Cat and dog allergy.
• Insect sting allergy.

How does allergen immunotherapy work?

Allergen immunotherapy involves giving small, carefully controlled doses of the allergen responsible for symptoms. These doses are increased gradually over time.

This process helps the immune system build tolerance, making it less likely to overreact when exposed to the allergen in everyday life.

In people with allergies, the immune system mistakenly identifies harmless substances, known as allergens, such as pollen or dust mites as a threat. This triggers the release of chemicals like histamine, which cause symptoms including sneezing, itching, and inflammation.

Immunotherapy works by:

• Reducing the immune system’s sensitivity to allergens.
• Decreasing the production of allergy-related antibodies.
• Increasing the body’s tolerance to triggers.

As a result, allergic reactions become less severe or may stop altogether.

Types of allergen immunotherapy

There are two main forms of allergen immunotherapy in clinical practice:

Subcutaneous immunotherapy (SCIT)

This treatment is given as a series of injections, usually in a specialist clinic. It typically begins with weekly injections before progressing to monthly maintenance doses.

Sublingual immunotherapy (SLIT)

Sublingual immunotherapy is taken at home in the form of daily tablets or drops placed under the tongue. It is a convenient alternative for suitable patients and is commonly used for pollen and dust mite allergies.

Who is suitable for allergen immunotherapy?

Allergen immunotherapy may be recommended for patients who:

• Have moderate to severe allergy symptoms.
• Do not respond well to standard medications.
• Experience side effects from medication.
• Wish to reduce long-term reliance on drug treatment.

A full allergy assessment by a specialist is required to determine suitability.

Allergen immunotherapy offers a unique approach to treating allergies by targeting the underlying cause rather than simply managing symptoms. A consultation with a consultant allergist can help determine whether this treatment is appropriate based on individual symptoms and medical history.