Desensitization therapy is a long-term treatment approach that fundamentally alters the immune system’s response to allergens. Unlike medications (such as antihistamines or steroid sprays) that temporarily “suppress” symptoms, it acts like an immune coach, continuously “training” the body to shift from an overreactive state (attack) to immune tolerance (acceptance), ultimately achieving long-term relief or even a cure.

I. Core Principle: From “Attack” to “Acceptance”

Imagine the immune system as a highly alert army that mistakes harmless substances like pollen or dust mites (allergens) for dangerous enemies. Upon detection, it launches a fierce attack, triggering allergic symptoms.

Desensitization therapy works as follows:

1. Start with a tiny dose: Introduce a minuscule amount of the “imagined enemy” (purified allergen extract) to the immune system.
2. Gradually increase the dose: Allow the immune system to slowly adapt to the presence of the allergen and recognize it as non-threatening.
3. Sustain maintenance: Administer long-term maintenance doses to solidify a state of “peaceful coexistence.”

During this process, the immune system undergoes tangible changes:

• Reduces the production of allergen-specific immunoglobulin E (IgE).
• Stimulates the production of immunoglobulin G (IgG4), a “blocking antibody” that acts like a shield. It binds to allergens in advance, preventing them from triggering IgE and mast cells, thereby stopping allergic reactions.
• Promotes the generation of regulatory T cells (Tregs), which effectively suppress excessive immune responses and maintain immune balance.

II. Treatment Process

The entire desensitization therapy course typically lasts 3–5 years and consists of two main phases:

1. Dose Escalation Phase (Initiation Phase)

• Gradually increase the dose to help the immune system adapt until an effective and sustainable target dose is reached. This phase usually lasts 3–6 months.

Method 1: Subcutaneous Immunotherapy (SCIT)

• Weekly injections at a clinic.
• The dose is slightly increased with each injection.
• After each injection, the patient must be observed at the clinic for at least 30 minutesto monitor for acute allergic reactions (e.g., difficulty breathing, severe hives) and ensure prompt medical intervention if needed.

Method 2: Sublingual Immunotherapy (SLIT)

• The first dose is usually taken under medical supervision.
• Thereafter, patients can self-administer daily at home(tablets or drops).
• The medication is held under the tongue for 1–2 minutes for mucosal absorption before swallowing.
• The dose escalation phase is shorter, often completed within days or weeks.

2. Maintenance Phase

• Stimulate the immune system with long-term “target maintenance doses” to consolidate and enhance tolerance for sustained effects. This phase is the core of the treatment and lasts 3–5 years.

Method 1: Subcutaneous Immunotherapy (SCIT)

• After reaching the target dose, injection intervals are gradually extended to once every 2–4 weeks.

Method 2: Sublingual Immunotherapy (SLIT)

• Patients must continue daily medication without interruption.

The success of the entire desensitization therapy highly depends on patient compliance. Interrupting or discontinuing treatment prematurely may nullify all progress, and the effects may not be sustained.

III. Applicability and Efficacy

Suitable for:

• Respiratory allergies: Highly effective against allergic rhinitis, allergic conjunctivitis, and asthma triggered by dust mites, pollen (grass, tree, weed), mold, or pet dander (e.g., cats, dogs).
• Insect venom allergies: Extremely effective (success rate >90%) for patients with severe allergic reactions to bee or wasp stings.

Less commonly used (still under research):

• Food allergies: Currently, only peanut desensitization therapy is approved. Treatments for other food allergies are mostly in clinical trials and must be conducted with extreme caution at specialized medical centers.
• Severe or uncontrolled asthma: Not suitable for this therapy due to the risk of triggering severe attacks.

IV. Potential Risks and Side Effects

Desensitization therapy is generally safe. However, since it involves active exposure to allergens, side effects may occur. These are generally categorized into local reactions (more common) and systemic reactions (less common but require vigilance).

Local Reactions

• Injection site: Redness, itching, induration (usually resolves within days).
• Oral/sublingual: Itching, mild swelling of the sublingual mucosa, throat discomfort (usually occurs shortly after administration and diminishes over time).

Systemic Reactions

• Symptoms may include widespread hives, asthma attacks, throat swelling, nausea, or abdominal pain.
• The most severe reaction is anaphylaxis, though it is extremely rare. This is why observation after subcutaneous injections and medical supervision during treatment are mandatory.

V. Efficacy and Important Considerations

Studies show that immunotherapy significantly alleviates symptoms, reduces the need for medication, and improves quality of life. Its effects can persist for years after treatment ends. For insect venom allergies, the efficacy rate exceeds 90%.

However, it may not work for everyone and requires considerable patience and adherence. Self-administration is strictly prohibited. Treatment must be guided and supervised by a physician to ensure safety and efficacy.

For assistance, please contact ENT Head and Neck Surgery Centre  (Tel: 3100 0555), where our ENT specialists will provide detailed diagnosis and formulate a treatment plan for you.

Source:

HK ENT Specialist Ltd.

ENT Head and Neck Surgery Centre

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