Allergen Immunotherapy (AIT) is a fundamental treatment approach for allergic reactions, involving long-term, regular exposure to allergens to modulate the immune system's response. Its primary goal is to reduce patients' hypersensitivity to specific allergens, thereby decreasing the frequency and severity of symptoms. Unlike conventional anti-allergy medications, this therapy can induce long-term immune regulation and may even achieve permanent symptom improvement.
Dessensitization therapy mainly falls into two categories: Subcutaneous Immunotherapy (SCIT) and Sublingual Immunotherapy (SLIT). SCIT involves gradually increasing allergen concentrations via subcutaneous injections, while SLIT administers allergens through oral mucosa under the tongue. The mechanisms include inducing regulatory T cell differentiation, increasing IgG blocking antibodies, and modulating Th1/Th2 cytokine balance, ultimately reducing IgE-mediated allergic reactions.
This therapy is primarily used for treating Type I hypersensitivity-related diseases, including perennial allergic rhinitis, seasonal allergic rhinoconjunctivitis, and asthma. For moderate to severe symptoms caused by specific allergens such as dust mites, pollen, or pet dander, when pharmacotherapy is insufficient, immunotherapy can be considered. Recent studies also suggest potential efficacy for bee venom allergy and certain drug allergies.
SCIT requires a build-up phase and a maintenance phase. During the build-up phase, weekly injections gradually increase the dose, while in the maintenance phase, injections are given every 4-6 weeks at a fixed dose. The entire course typically lasts 3-5 years. SLIT involves daily sublingual administration of specific allergen extracts, with a longer treatment duration of usually 3-5 years. Dose adjustments are made based on allergen test results and symptom responses.
This therapy offers a disease-modifying effect, reducing airway hyperresponsiveness and improving lung function. Long-term follow-up shows that approximately 70-80% of patients experience symptom relief after completing the course, with evidence indicating a reduced risk of developing new sensitivities. Compared to standard medications, its benefits can last for several years and reduce long-term medication dependence.
Potential risks include local reactions such as redness or itching at the injection site, and in severe cases, systemic allergic reactions (anaphylaxis). The incidence of severe reactions in SCIT is about 0.01-0.2%, while oral itching or throat discomfort occurs in approximately 30-50% of SLIT patients. Initial injections must be monitored in a medical facility for at least 30 minutes, and patients should carry an epinephrine auto-injector for emergencies.
Contraindications include uncontrolled severe airway obstruction, cardiovascular diseases, or immunodeficiency disorders. During treatment, live vaccines should be avoided, and it is recommended to suspend therapy during early pregnancy. Patients should undergo skin prick testing and serum-specific IgE testing before treatment to confirm allergen types and appropriate dosing.
Combination with antihistamines may alleviate symptoms but does not affect the efficacy of immunotherapy. Use of corticosteroids or anti-IgE monoclonal antibodies may alter treatment outcomes; patients should inform their healthcare provider of all medications they are using. Concurrent use of allergen-specific immunotherapy (such as sublingual and subcutaneous) should be avoided to prevent increased risks.
Multicenter randomized controlled trials show that SCIT improves symptoms in pollen allergy patients by 60-70% and reduces steroid use by 50%. Lung function indices (FEV1) in asthma patients improve by an average of 10-15%. Twenty-year follow-up studies confirm sustained benefits after therapy completion, with some patients experiencing long-term remission lasting 5-10 years.
Alternatives include antihistamines, intranasal corticosteroids, and monoclonal antibody drugs (such as omalizumab). These therapies can quickly relieve symptoms but do not provide a fundamental cure. Allergen avoidance measures are effective but difficult to fully implement for environmental allergens like dust mites. Emerging sublingual therapies and traditional injections each have their advantages and disadvantages, and should be chosen based on patient preference.
Before treatment, patients should undergo skin prick testing or blood tests to identify specific allergens. The doctor will evaluate overall health, especially lung and heart function, and check for severe complications. Patients should stop certain antihistamines at least 48 hours prior and avoid alcohol on the day of treatment.
What should I do if I experience redness or itching at the injection site during treatment?Minor redness can be relieved with ice packs for 10-15 minutes and avoiding scratching. If blisters, persistent swelling, or systemic symptoms like difficulty breathing occur, stop injections immediately and contact the medical team. The doctor may adjust the dose or prescribe short-term corticosteroids to suppress overreaction.
Are there dietary or activity restrictions during treatment?It is recommended to avoid vigorous exercise within 2 hours after treatment to reduce systemic reactions. Avoid spicy foods and alcohol, as they may trigger allergic symptoms. On treatment days, opt for a light diet and stay well-hydrated to promote metabolic stability.
How often should I follow up after completing treatment?Follow-up is recommended every 3-6 months in the first year after treatment, then annually. The doctor will monitor allergic response through skin prick testing or serum IgE levels. If symptoms recur, re-evaluation may be needed to determine if additional courses or preventive measures are necessary.
How long does the long-term protective effect of desensitization last?Studies show that patients who complete more than 3 years of therapy can experience symptom relief for 3-5 years. The duration of protection depends on the allergen type and immune response; dust mite immunotherapy tends to have more lasting effects than pollen allergy. Continued avoidance of allergens can significantly prolong the benefits.
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