Overview
Definition:
Venom allergy in children is an exaggerated immune response to venom from stinging insects, primarily hymenoptera (bees, wasps, hornets, fire ants), leading to potentially severe systemic reactions.
Epidemiology:
While anaphylaxis from insect stings is rare in children, it can occur
The incidence of sting reactions varies geographically and by insect species
Recurrent stings increase the risk of sensitization and severe reactions.
Clinical Significance:
Prompt and accurate diagnosis is crucial to prevent life-threatening anaphylaxis in sensitized children
Understanding testing and immunotherapy options is vital for pediatricians preparing for DNB and NEET SS examinations, enabling effective patient management and improved outcomes.
Clinical Presentation
Symptoms:
Local reactions: Erythema, swelling, pain, and itching at the sting site
Systemic reactions: Urticaria, angioedema, pruritus, rhinitis, conjunctivitis, bronchospasm, stridor, gastrointestinal symptoms (nausea, vomiting, diarrhea), dizziness, syncope, hypotension, and anaphylaxis.
Signs:
Local reactions usually limited to the sting site
Systemic reactions may include widespread hives, facial/limb swelling, wheezing, laryngeal edema, tachycardia, and a drop in blood pressure
Severe reactions can lead to shock.
Diagnostic Criteria:
Diagnosis is typically based on a history of systemic reaction following an insect sting in a child, confirmed by positive venom-specific IgE testing
Grading of reaction severity is important for management decisions.
Diagnostic Approach
History Taking:
Detailed history of the sting event, including insect type (if known), number of stings, time elapsed, symptoms experienced, progression of symptoms, previous sting reactions, and family history of atopy or anaphylaxis
Crucial for identifying risk factors and guiding testing.
Physical Examination:
Thorough examination focusing on signs of systemic involvement: skin for urticaria/angioedema, respiratory system for wheezing/stridor, cardiovascular system for heart rate and blood pressure
Assess the sting site for local reaction severity.
Investigations:
Venom-specific IgE testing (skin prick tests and/or serum specific IgE) is the cornerstone
Skin prick tests (SPT) are typically performed first
If SPT is negative but suspicion remains high, intradermal tests (IDT) may be considered
Quantiferon-TB Gold Test should be ruled out for allergic reactions of unknown etiology
Interpret results in conjunction with clinical history.
Differential Diagnosis:
Vasovagal syncope, food allergies, drug reactions, idiopathic urticaria, mastocytosis, and anxiety reactions can mimic insect sting reactions
Careful history and specific IgE testing help differentiate.
Management
Initial Management:
For mild local reactions: cool compresses, antihistamines, and topical corticosteroids
For systemic reactions/anaphylaxis: immediate administration of intramuscular epinephrine (0.01 mg/kg, max 0.3 mg for children <30 kg
max 0.5 mg for children >30 kg)
Call emergency services
Airway management, oxygen, intravenous fluids, and corticosteroids may be required.
Medical Management:
Antihistamines (oral H1 blockers) are useful for urticaria and pruritus
Oral corticosteroids may be used for severe local or systemic reactions
Epinephrine is the drug of choice for anaphylaxis.
Immunotherapy:
Venom immunotherapy (VIT) is highly effective in preventing recurrent systemic reactions in children with documented venom allergy
It involves gradually increasing doses of venom extract to induce tolerance
Typically administered for 3-5 years
Indicated for children with a history of anaphylaxis to a hymenoptera sting and positive venom-specific IgE.
Supportive Care:
Patient and family education on sting avoidance, recognition of early symptoms, and emergency management (including epinephrine auto-injector use)
Regular follow-up to monitor response to immunotherapy and assess ongoing risk.
Complications
Early Complications:
Anaphylaxis, airway obstruction, cardiovascular collapse, and secondary infections at the sting site.
Late Complications:
Psychological distress, phobia of insects, and potential for severe reactions upon future stings if untreated
Recurrence of anaphylaxis if immunotherapy is stopped prematurely or not initiated.
Prevention Strategies:
Strict avoidance of insect habitats, wearing protective clothing, using insect repellents, and prompt administration of epinephrine in case of a sting in sensitized individuals
Educating families on recognition and management of reactions.
Prognosis
Factors Affecting Prognosis:
Severity of the initial reaction, promptness of treatment, adherence to immunotherapy, and avoidance of future stings
Children with anaphylaxis and those undergoing VIT generally have a good prognosis with appropriate management.
Outcomes:
Successful venom immunotherapy is highly effective, reducing the risk of systemic reactions to <10%
Most children can eventually discontinue VIT after several years with sustained protection.
Follow Up:
Regular follow-up with an allergist is essential during VIT to monitor for adverse reactions, assess adherence, and plan for discontinuation
Long-term follow-up may be recommended for high-risk individuals.
Key Points
Exam Focus:
Recognize hymenoptera species associated with venom allergy
Understand indications for venom-specific IgE testing
Know the protocols for immediate management of anaphylaxis, including epinephrine dosage
Identify candidates for venom immunotherapy and its duration
Differentiate between local and systemic reactions.
Clinical Pearls:
Always carry an epinephrine auto-injector if diagnosed with venom allergy
Educate families on sting avoidance strategies
Reassure parents that VIT is safe and highly effective
Consider delayed but severe reactions in some cases.
Common Mistakes:
Underestimating the severity of systemic reactions
Delaying epinephrine administration
Inappropriate use of oral antihistamines or corticosteroids as sole treatment for anaphylaxis
Failing to refer for immunotherapy when indicated
Incorrect interpretation of venom-specific IgE results without clinical correlation.