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Immunotherapy (desensitisation)

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What is allergen desensitisation/ sublingual immunotherapy?

Sublingual immunotherapy (SLIT) is a form of treatment designed to alleviate allergies by gradually desensitizing the immune system to specific allergens. Unlike traditional allergy shots (subcutaneous immunotherapy), SLIT involves placing allergen extracts under the tongue. This comprehensive guide will explore the principles, effectiveness, safety, and potential benefits of sublingual immunotherapy.

Introduction to Sublingual Immunotherapy (SLIT)

Allergies occur when the immune system reacts excessively to harmless substances, triggering symptoms such as sneezing, itching, and nasal congestion. Sublingual immunotherapy offers an alternative approach to managing allergies by utilizing the body's natural immune response.

How SLIT Works

Identification of Allergens:

Before initiating sublingual immunotherapy, a thorough allergy assessment is conducted to identify specific allergens causing symptoms. Common allergens include pollen, dust mites, pet dander, and molds.

Customized Allergen Extracts:

Allergen extracts are formulated based on the individual's specific allergic triggers. These extracts are derived from the substances causing allergies and are prepared in a controlled environment.

Under-the-Tongue Administration:

Small doses of allergen extracts are placed under the tongue (sublingual region) daily. The mucous membranes under the tongue facilitate the absorption of the allergen extracts into the bloodstream.

Gradual Desensitization:

The principle behind SLIT is to expose the immune system to gradually increasing amounts of allergens. This exposure aims to induce immunological tolerance, reducing the immune response and minimizing allergic symptoms over time.

Effectiveness of Sublingual Immunotherapy

Numerous clinical studies have demonstrated the effectiveness of SLIT in managing allergic rhinitis, with improvements in symptoms such as sneezing, nasal congestion, and itchy eyes. The European Academy of Allergy and Clinical Immunology (EAACI) supports the use of SLIT for allergic rhinitis.


SLIT has also shown promise in managing allergic asthma, with some studies reporting a reduction in asthma symptoms and the need for rescue medications. However, its use for asthma is still under investigation, and further research is needed.

Environmental Allergies:

SLIT is effective for various environmental allergies, including pollen, dust mites, and pet dander. Positive outcomes have been observed in both children and adults. 

Safety and Side Effects

Local Reactions:

The most common side effects of SLIT are mild and occur locally in the mouth, such as oral itching or swelling. These reactions are usually transient and resolve on their own.

Systemic Reactions:

Serious systemic reactions are rare with SLIT compared to traditional subcutaneous immunotherapy. However, patients must be monitored closely during the initial doses to detect any potential adverse effects.


Treatment Duration:

SLIT is typically administered over an extended period, ranging from several months to years. Long-term safety studies have shown a favorable safety profile for SLIT. 


Benefits of Sublingual Immunotherapy


SLIT offers a convenient at-home administration option, reducing the need for frequent clinic visits. Patients can self-administer the treatment under medical supervision.

Reduced Risk of Anaphylaxis:

SLIT has a lower risk of severe allergic reactions (anaphylaxis) compared to subcutaneous immunotherapy. This makes it a safer option for individuals who may be at higher risk of anaphylactic reactions.

Pediatric Application:

SLIT is considered safe and effective for children, offering a viable treatment option for pediatric allergies. It has been used in children as young as 5 years old.

Considerations and Limitations

Individualized Treatment:

SLIT requires a personalized approach, with allergen extracts tailored to each patient's specific allergies.

The effectiveness may vary based on individual responses.

Time Commitment:

Sublingual immunotherapy is a long-term commitment, and patients need to adhere to the prescribed treatment plan for optimal results.

The gradual desensitization process takes time.

Not Suitable for All Allergens:

While effective for certain allergens, SLIT may not be suitable for all types of allergies.

Some allergens may require alternative forms of immunotherapy.


Sublingual immunotherapy represents a valuable treatment option for individuals suffering from allergic rhinitis, asthma, and environmental allergies. Its effectiveness, safety profile, and convenience make it an appealing choice for both adults and children. As research continues to expand our understanding of immunotherapy, sublingual administration stands as a promising avenue for improving the quality of life for allergy sufferers. However, it is crucial for patients to consult with healthcare professionals to determine the most suitable treatment plan based on their specific allergies and medical history.

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