Overview
Definition:
Allergen immunotherapy (AIT) is a disease-modifying treatment that involves administering gradually increasing doses of specific allergens to allergic individuals to induce immunological tolerance
It is a cornerstone in the management of IgE-mediated allergic diseases, particularly allergic rhinitis and asthma, in children.
Epidemiology:
Allergic rhinitis and asthma are highly prevalent in pediatric populations globally, affecting millions of children
Studies indicate that a significant proportion of children with allergic rhinitis also have asthma, and allergen immunotherapy has shown efficacy in reducing symptoms and improving quality of life in these patients.
Clinical Significance:
AIT offers a unique opportunity to alter the natural course of allergic diseases in children, potentially preventing the development of new allergies and progression to more severe asthma
It addresses the underlying immunological mechanisms, leading to sustained symptom relief and reduced medication requirements, thereby improving long-term health outcomes and reducing the burden of allergic disease.
Indications
Allergic Rhinitis:
Persistent moderate to severe allergic rhinitis inadequately controlled by avoidance and pharmacological therapy
presence of specific IgE antibodies to common aeroallergens (e.g., dust mites, pollens, molds, animal danders)
desire to reduce reliance on medications
prevention of allergic march (development of asthma).
Allergic Asthma:
Allergic asthma with evidence of allergen sensitization, where symptoms are predominantly triggered by specific allergens and are not adequately controlled with conventional asthma therapies
often used in conjunction with AIT for allergic rhinitis.
Other Indications:
Allergic conjunctivitis
venom immunotherapy for insect sting allergy (though less common in routine pediatric rhinitis/asthma practice)
prophylactic treatment in select cases to prevent allergic sensitization.
Contraindications
Absolute Contraindications:
Severe uncontrolled asthma (FEV1 < 70% predicted)
use of beta-blockers which can blunt the response to adrenaline during anaphylaxis
severe immunodeficiency disorders
certain cardiovascular conditions.
Relative Contraindications:
Specific allergen not identifiable or available
pregnancy (although AIT is generally not initiated in pregnancy, continuation may be considered)
certain autoimmune diseases
patients with significant comorbidities that may increase risk
history of severe anaphylactic reactions to previous immunotherapy.
Age Considerations:
Generally recommended for children aged 5 years and above, though individualized assessment is crucial
Younger children may be considered if symptoms are severe and impact significantly on quality of life and if parental compliance can be ensured.
Diagnostic Approach
History Taking:
Detailed history of symptoms (onset, duration, seasonality, triggers)
presence of atopy in family members
response to previous treatments
impact on daily activities, sleep, and school performance
history of anaphylaxis
specific allergen exposure assessment.
Physical Examination:
Examination of nasal mucosa (pallor, edema, polyps)
assessment for allergic shiners, Dennie-Morgan lines, orofacial structures
auscultation of lungs for wheezing or decreased breath sounds
examination for skin manifestations of atopy (eczema).
Investigations:
Allergen-specific IgE testing: Skin prick testing (SPT) using standardized allergen extracts is the gold standard for identifying sensitizations
Serum specific IgE (RAST/ImmunoCAP) can be used as an alternative, especially when SPT is contraindicated or technically difficult
Component-resolved diagnostics (CRD) can provide further insights into allergen specificity.
Differential Diagnosis:
Non-allergic rhinitis (vasomotor, irritant, gustatory)
chronic sinusitis
adenoid hypertrophy
foreign body in the nose
cystic fibrosis
immune deficiencies.
Management
Immunotherapy Options:
Subcutaneous immunotherapy (SCIT): Administered via subcutaneous injections in increasing doses
Sublingual immunotherapy (SLIT): Administered as drops or tablets under the tongue
Both are effective, with SLIT offering the advantage of home administration after initial supervision.
Scit Protocols:
Build-up phase: Frequent injections (1-2 times/week) with gradually increasing allergen dose
Maintenance phase: Less frequent injections (monthly) with the highest tolerated dose for 3-5 years
Dose escalation is guided by local and systemic reactions.
Slit Protocols:
Daily administration of allergen extract under the tongue
Available as standardized tablets for specific allergens (e.g., grass pollens, dust mites)
Duration of treatment is typically 3-5 years.
Adjunctive Therapies:
Pharmacological treatments such as intranasal corticosteroids, antihistamines, and leukotriene receptor antagonists may be used concurrently to manage symptoms, especially during the initial phases of immunotherapy or for breakthrough symptoms
Allergen avoidance measures are also crucial.
Adverse Effects And Monitoring
Local Reactions:
Common with SCIT: Erythema, itching, swelling at the injection site
Usually managed by dose adjustment or temporarily withholding therapy
SLIT can cause oral pruritus, mild swelling of the tongue or lips.
Systemic Reactions:
Less common but more serious: Urticaria, angioedema, bronchospasm, gastrointestinal symptoms, and anaphylaxis
Anaphylaxis is a rare but life-threatening complication, requiring immediate adrenaline administration
SLIT-related systemic reactions are generally milder.
Monitoring Requirements:
Close monitoring for adverse reactions is essential, especially during the build-up phase of SCIT
Patients on SCIT should be observed for at least 20-30 minutes post-injection
Regular follow-up with the allergist or pediatrician to assess symptom control, medication use, and adherence to therapy is vital
FEV1 monitoring is important for asthmatic patients.
Key Points
Exam Focus:
AIT is a disease-modifying treatment for IgE-mediated allergies
SCIT and SLIT are the main modalities
Indications include persistent, symptomatic allergic rhinitis/asthma uncontrolled by conventional therapy
Contraindications must be carefully assessed
Anaphylaxis is the most serious adverse event for SCIT.
Clinical Pearls:
Start immunotherapy with allergens identified by history and confirmed by testing
Always have an epinephrine auto-injector readily available for SCIT
Educate parents thoroughly on the risks, benefits, and administration of AIT
Individualize treatment based on patient response and tolerance.
Common Mistakes:
Initiating immunotherapy without clear evidence of allergen sensitization
failing to adequately assess contraindications
inadequate observation period post-SCIT injection
prescribing AIT for non-allergic conditions
poor patient education leading to non-adherence or misunderstanding of risks.