Overview
Definition:
Oral immunotherapy (OIT) is a treatment modality aimed at increasing tolerance to specific food allergens, such as peanut, through controlled, sequential oral administration of increasing doses of the allergen
The goal is not necessarily complete desensitization, but rather inducing a state of sustained tolerance that protects against accidental exposure and reduces the severity of reactions
It is distinct from emergency treatment of anaphylaxis.
Epidemiology:
Peanut allergy is one of the most common and severe food allergies in children and adults, with increasing prevalence globally
It accounts for a significant proportion of food-induced anaphylaxis and fatalities
Approximately 1-2% of children and 0.5-1% of adults in Western countries are estimated to have peanut allergy
OIT has emerged as a promising therapeutic option for select individuals.
Clinical Significance:
For pediatric residents and DNB/NEET SS aspirants, understanding OIT is crucial due to the high prevalence of peanut allergy and its potential for severe reactions
OIT offers a way to reduce the risk of accidental ingestions leading to anaphylaxis, improve quality of life, and alleviate the constant anxiety associated with severe food allergies
Proper patient selection, meticulous monitoring, and management of adverse events are paramount for successful and safe OIT.
Indications
Patient Selection:
OIT is typically considered for individuals with confirmed peanut allergy, usually diagnosed by a history of allergic reaction, positive skin prick test (SPT), and/or specific IgE levels
Key indications include recurrent reactions from trace exposures, significant impact on quality of life, and failure to adhere to strict avoidance
Age 4 years and above is generally recommended, though research is ongoing for younger populations
Patients must demonstrate commitment to the rigorous protocol.
Contraindications:
Absolute contraindications include uncontrolled asthma, eosinophilic esophagitis (EoE) active or recent, history of anaphylaxis to other foods requiring epinephrine in the past 6 months, other significant comorbidities, and inability to adhere to treatment
Relative contraindications include poorly controlled asthma, gastrointestinal disorders like inflammatory bowel disease, and significant cardiac conditions.
Risk Benefit Assessment:
A thorough assessment is required before initiating OIT
Benefits include reduced risk of anaphylaxis, increased tolerance, and improved quality of life
Risks include dose-dependent reactions during escalation (oral symptoms, urticaria, gastrointestinal upset, anaphylaxis), potential for daily side effects (e.g., oral pruritus), and the need for strict adherence
The decision must be individualized, balancing potential benefits against risks.
Patient And Family Education:
Comprehensive education for the patient and family is a prerequisite for OIT
This includes understanding the rationale for OIT, the stages of treatment, potential adverse reactions and their management (including epinephrine auto-injector use), the importance of adherence, and the need for regular follow-up
Realistic expectations about the process and outcomes must be set.
Initiation And Updosing
Initial Dose Administration:
OIT typically begins with a very small, sub-threshold dose of peanut protein, administered under strict medical supervision in a clinical setting (e.g., allergy clinic)
Vital signs, oxygen saturation, and symptoms are closely monitored for at least 30-60 minutes post-dose, and sometimes longer, depending on the patient's history and tolerance.
Dose Escalation Protocol:
Following successful administration of the initial dose with no or mild, transient reactions, the dose is gradually increased over weeks to months
This usually involves daily increases in oral peanut protein intake, with doses doubling or increasing by defined increments
The rate of escalation is individualized and depends on the patient's tolerance
Home dosing is initiated after successful in-clinic escalation.
Monitoring During Escalation:
Patients are educated to report any symptoms promptly
Common side effects include oral pruritus, mild urticaria, gastrointestinal discomfort (nausea, vomiting, diarrhea), and cough
Significant reactions, including systemic symptoms or anaphylaxis, necessitate immediate cessation of dose escalation and may require emergency treatment
If symptoms are mild and transient, the same dose may be repeated, or a slightly reduced dose may be used the next day before resuming escalation.
Food Avoidance Recommendations:
While on OIT, strict avoidance of peanut and cross-reactive allergens remains essential to prevent accidental exposures that could trigger a reaction and compromise OIT progress
Patients should not consume other nuts or tree nuts until their safety has been assessed, as cross-reactivity can occur.
Monitoring And Management Of Adverse Events
Signs And Symptoms Of Reactions:
Adverse events can range from mild oral symptoms (itching, tingling in the mouth) and gastrointestinal upset to more severe manifestations like urticaria, angioedema, wheezing, stridor, hypotension, and anaphylaxis
Allergic rhinitis, conjunctivitis, and cough are also common
Gastrointestinal symptoms are frequent, especially with initial doses or rapid escalation.
Management Of Mild Reactions:
Mild oral pruritus or mild gastrointestinal upset may be managed by repeating the current dose or slightly reducing the next dose
Antihistamines may be used for symptomatic relief
The patient should be monitored for resolution of symptoms before proceeding.
Management Of Moderate To Severe Reactions:
Moderate reactions (e.g., generalized urticaria, mild bronchospasm) and severe reactions (anaphylaxis) require immediate discontinuation of OIT and administration of epinephrine
Patients must be trained in the use of epinephrine auto-injectors and advised to seek immediate medical attention
This may involve discontinuing OIT temporarily or permanently, depending on the severity and recurrent nature of the reactions.
Long Term Monitoring And Adherence:
Regular follow-up with an allergist is critical throughout OIT
This involves assessing tolerance, monitoring for adverse events, and evaluating the level of protection achieved
Adherence to the daily dosing schedule is crucial for success
Patients who miss doses or have significant reactions may require re-titration to lower doses
Ongoing monitoring of asthma control and other comorbidities is also important.
Long Term Outcomes And Discontinuation
Achieving Maintenance Dose:
The goal of OIT is to reach a sustained maintenance dose, typically equivalent to one to two whole peanuts per day, which confers a significant level of protection against accidental exposure
This process can take many months to over a year.
Sustained Unresponsiveness:
While OIT aims to induce tolerance, the exact mechanism and duration of this tolerance are still under investigation
Some patients may experience sustained unresponsiveness even after discontinuing OIT, while others may revert to allergic status, necessitating re-initiation of OIT or continued avoidance.
Criteria For Discontinuation:
Discontinuation of OIT may be considered if the patient consistently experiences significant adverse events, if adherence becomes problematic, if the patient develops uncontrolled comorbidities (e.g., asthma), or if the defined treatment duration is completed and a satisfactory level of tolerance is achieved
Some protocols suggest a period of maintenance followed by assessment of oral tolerance, with potential for tapering.
Impact On Quality Of Life:
Successful OIT can significantly improve the quality of life for individuals with peanut allergy by reducing the fear of accidental ingestion, allowing for greater participation in social activities, and decreasing the burden of strict avoidance
However, the psychological burden of managing a chronic condition and the potential for adverse events must be acknowledged.
Key Points
Exam Focus:
Understand the principle of OIT for peanut allergy, distinguishing it from emergency management
Know the indications, absolute contraindications (uncontrolled asthma, EoE), and the stepwise approach to dose escalation
Be aware of common adverse reactions (oral pruritus, GI upset, urticaria, anaphylaxis) and their immediate management, including the role of epinephrine.
Clinical Pearls:
Individualize OIT protocols based on patient tolerance and response
Emphasize patient/family education on adherence and emergency preparedness
Recognize that OIT is a treatment for reducing reactivity, not a cure, and strict avoidance is still necessary
Monitor for delayed reactions and ensure proper management of comorbidities like asthma.
Common Mistakes:
Initiating OIT in patients with uncontrolled asthma or other contraindications
Underestimating the risk of anaphylaxis during dose escalation
Inadequate patient/family education regarding adherence and emergency response
Failing to individualize the OIT protocol based on patient tolerance
Misinterpreting mild local symptoms as non-significant without careful follow-up.