Immunotherapy for allergies

Overview of Treatment

Allergen Immunotherapy (AIT) is a treatment targeting the root cause of allergies. It involves long-term and gradual exposure to allergens to recalibrate the immune system's response. This therapy is mainly suitable for patients with chronic allergies, such as hay fever, dust mite allergy, or insect venom allergy, effectively reducing symptom severity and decreasing reliance on allergy medications. Unlike symptomatic relief drugs, the goal of immunotherapy is to produce long-lasting immune tolerance, typically requiring continuous treatment for 3 to 5 years to see results.

Types and Mechanisms of Treatment

Immunotherapy is divided into Subcutaneous Immunotherapy (SCIT) and Sublingual Immunotherapy (SLIT). SCIT requires administration by healthcare professionals at medical facilities, while SLIT can be self-administered at home using sublingual tablets. The mechanism involves small doses of allergens stimulating the production of blocking IgG antibodies and regulating the Th1/Th2 cytokine balance, ultimately reducing the overreaction of IgE antibodies associated with allergies.

Indications

This therapy is suitable for patients with clear diagnoses of specific allergens, including:

• Perennial allergic rhinitis
• Asthma with allergic components
• Insect venom allergy (e.g., bee or wasp venom)
• Severe dust mite or mold allergy

For those unable to avoid allergen exposure, with severe symptoms affecting quality of life, or with resistance to conventional medications, immunotherapy is the preferred option.

Usage and Dosage

SCIT treatment involves build-up and maintenance phases: the build-up phase starts with very small doses, gradually increasing concentration weekly over approximately 3 to 6 months; the maintenance phase involves fixed doses administered once a month. SLIT involves daily fixed doses of sublingual tablets, swallowed after 15 minutes. The duration of treatment is similar to SCIT. Dose adjustments should be based on the severity of allergy and patient tolerance, and self-modification of dosage is strictly prohibited.

Benefits and Advantages

Main benefits include:

• Long-lasting symptom relief: improvements can last for several years to a decade after treatment
• Reduced risk of allergy exacerbation: decreases frequency and severity of asthma attacks
• Reduced medication dependence: patients on long-term antihistamines or steroid nasal sprays can gradually reduce usage

This therapy has also been proven to lower the risk of developing sensitivities to new allergens, exhibiting disease-modifying effects.

Risks and Side Effects

Common side effects include:

• SCIT may cause redness or itching at the injection site
• SLIT may cause oral discomfort or mild throat itching

Serious risks: Rarely, patients may experience systemic allergic reactions such as difficulty breathing or hypotension, requiring administration under medical supervision during the first injection. During treatment, vital signs and symptoms should be regularly monitored.

Precautions and Contraindications

Contraindications include:

• Severe uncontrolled asthma or cardiopulmonary diseases
• Immunodeficiency or ongoing immunosuppressive therapy
• Uncontrolled thyroid or cardiovascular diseases

During treatment, live vaccines should be avoided, and women are advised to avoid pregnancy. If abnormal reactions such as difficulty breathing occur, treatment should be stopped immediately and medical attention sought.

Interactions with Other Treatments

When used with antihistamines, dosage adjustments may be necessary, as some antihistamines can affect efficacy. Combining with corticosteroid nasal sprays can enhance effects, but oral steroids may interfere with the mechanism of immunotherapy. Patients on biologic treatments for asthma should consult an allergy specialist beforehand to avoid drug interactions.

Effectiveness and Evidence

Clinical trials show that SCIT can reduce symptom severity by 60-80%, with effects lasting 3 to 5 years after completion. For dust mite allergy patients, SLIT achieves a 70% symptom improvement rate. Randomized controlled trials confirm that after immunotherapy, asthma patients reduce rescue inhaler use by an average of 40%. Efficacy varies among individuals and requires regular follow-up and adjustments.

Alternatives

Alternative options include:

• Antihistamines: provide rapid symptom relief but do not cure allergies
• Nasal corticosteroid sprays: control nasal inflammation but require long-term use
• Monoclonal antibodies (e.g., anti-IgE therapy): suitable for severe asthma with allergies, but are self-funded and require regular injections

These alternatives mainly target symptom management, whereas immunotherapy is the only treatment that may alter the natural course of allergies.

 

Frequently Asked Questions

How are the frequency and total duration of allergen immunotherapy scheduled?

Allergen immunotherapy is generally divided into the "build-up" and "maintenance" phases. Initially, injections are given weekly or biweekly, then transitioned to monthly fixed doses after about 3 to 6 months. The overall course usually lasts 3 to 5 years. The frequency of SCIT and SLIT may vary depending on the formulation, and personalized plans should be developed by a physician.

What should I do if I experience redness, swelling, or itching during treatment?

Mild local reactions are common and can be alleviated with ice packs and observation for 15 to 30 minutes. If systemic symptoms such as difficulty breathing occur, notify medical staff immediately and seek medical attention. The physician may adjust the dose or administer antihistamines to reduce the risk of reactions. Patients should be observed for 30 minutes after each treatment at the medical facility.

Do I need to avoid contact with allergens during treatment? What environmental controls should I pay attention to?

Allergen exposure should be minimized during treatment, such as using dust mite-proof bedding and regularly cleaning appliances for dust mite allergy. During pollen season, keep windows closed and use air filters. While immunotherapy gradually increases tolerance, environmental control can enhance efficacy and reduce the risk of symptom rebound.

How long does the long-term efficacy of allergen immunotherapy last? Will symptoms fully return after stopping medication?

After successful completion of therapy, about 70-80% of patients experience long-term relief for 3 to 5 years, with some even reducing allergic responses lifelong. Efficacy depends on regular injections during treatment, the type of allergen, and the patient's immune status. Symptoms may recur if exposed to allergens in large quantities after stopping, so maintaining basic environmental controls is recommended.

Can patients on antihistamines or nasal sprays undergo immunotherapy simultaneously?

Most allergy medications, such as antihistamines and nasal corticosteroid sprays, can be used concurrently with immunotherapy, but they may affect symptom assessment. Physicians usually recommend continuing control medications during the initial phase and gradually reducing doses once immunotherapy takes effect. Patients on corticosteroids or adrenaline should inform their doctor beforehand to avoid interfering with the treatment efficacy.