What is the recommended evaluation and management for a patient presenting with a suspected allergic condition, including history taking, trigger avoidance, pharmacologic therapy, anaphylaxis treatment, specialist referral, and patient education?

Evaluation and Management of Suspected Allergic Conditions

All patients presenting with suspected allergic conditions require a detailed clinical history focusing on cutaneous manifestations (pruritus, urticaria, angioedema), respiratory symptoms (upper or lower airway obstruction), gastrointestinal symptoms (nausea, vomiting, diarrhea), and cardiovascular symptoms (syncope, hypotension), with immediate referral to an allergist-immunologist for comprehensive diagnostic testing and long-term management. 1

Initial History Taking

Essential questions to establish allergic diagnosis:

• Cutaneous manifestations: Document presence of pruritus, flushing, urticaria, and angioedema (present in 90% of anaphylaxis cases, though absence does not rule out allergic reaction) 1, 2
• Airway involvement: Identify upper or lower airway obstruction, bronchospasm, wheezing, or laryngeal edema (occurs in 40-60% of anaphylaxis) 1, 2
• Gastrointestinal symptoms: Note nausea, vomiting, or diarrhea 1
• Cardiovascular symptoms: Document syncope, presyncope, hypotension, tachycardia, or cardiovascular collapse (present in 30-35% of cases) 1, 2

Obtain history from patient, family members, and witnesses when appropriate, reviewing complete sequence of events with special attention to cardiorespiratory symptoms 1

Document all agents encountered before the reaction:

• All foods and drugs ingested several hours before the episode, including review of packaged food labels for hidden ingredients like carmine 1
• Any preceding insect bites or stings 1
• Patient activities including exercise, sexual activity, or psychological stress preceding the event 1
• Review medical records, medication records, and any previous laboratory studies (serum tryptase levels) 1

Differential Diagnosis Considerations

If history is not consistent with allergic reaction, pursue alternative diagnoses: 1

• Vasodepressor (vasovagal-neurocardiogenic) syncope 1
• Syndromes associated with flushing (metastatic carcinoid) 1
• Postprandial syndromes (scombroid poisoning) 1
• Systemic mastocytosis 1
• Psychiatric disorders (panic attacks, vocal cord dysfunction syndrome) 1
• Angioedema (hereditary angioedema) 1
• Other causes of shock (cardiogenic) 1
• Other cardiovascular or respiratory events 1

Trigger Identification and Avoidance

History is the most important tool to establish the cause and takes precedence over diagnostic tests 1

Patient diaries are useful adjuncts in confirming and identifying triggers 1

Common triggers to investigate:

• Foods (peanuts, tree nuts, shellfish—most common cause of anaphylaxis outside hospital settings) 1, 2
• Medications (penicillin, beta-lactam antibiotics, NSAIDs) 1, 2
• Insect venoms (Hymenoptera stings cause 23% of anaphylaxis cases) 2
• Latex 1
• Exercise-induced or food-dependent exercise-induced anaphylaxis 1

If cause is not readily identified by history, proceed to diagnostic allergy testing through allergist-immunologist 1

Idiopathic anaphylaxis is a diagnosis of exclusion made only after other causes have been ruled out (accounts for 30-60% of adult cases and up to 10% of pediatric cases) 1, 3

Acute Anaphylaxis Treatment

Administer intramuscular epinephrine immediately at the first sign of anaphylaxis—this is the single most critical life-saving intervention with no absolute contraindication 4, 2, 5

Never delay epinephrine while considering other diagnoses or waiting for symptoms to worsen 4

Dosing:

• Adults: 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) IM into lateral thigh 4, 2
• Children ≥25 kg: 0.3 mg 4
• Children 10-25 kg: 0.15 mg 4

Repeat epinephrine every 5-15 minutes if inadequate response (7-18% of patients require more than one dose) 4, 2

Immediate supportive measures:

• Position patient supine with legs elevated (up to 50% of intravascular fluid can shift to extravascular space within 10 minutes) 4
• Call emergency medical services immediately 4
• Remove triggering agent if identifiable 4
• Establish airway and administer 100% oxygen, with intubation if necessary 4
• Rapid IV fluid resuscitation with normal saline or lactated Ringer's solution via large-bore IV 4
• Consider continuous IV epinephrine infusion if multiple doses required 4

Adjunctive medications (only after epinephrine administration):

• H1 antihistamine (chlorphenamine 10 mg IV or diphenhydramine) for urticaria and itching relief only 4, 2
• Corticosteroids (hydrocortisone 200 mg IV or methylprednisolone) have 4-6 hour onset, no immediate effect on acute anaphylaxis 4, 2
• Beta-2 agonists (salbutamol) for persistent bronchospasm 4

Observation Period

Observe patients for minimum 4-6 hours after symptom resolution for most cases 6, 4, 3

Extend observation or admit patients with:

• Severe reactions requiring multiple epinephrine doses 6, 4
• Cardiovascular comorbidity 6, 4
• Poor self-management capability 6, 4
• Wide pulse pressure 6
• Unknown trigger 6
• Drug triggers in children 6

Biphasic reactions occur in up to 20% of cases (1-7% in some studies), with symptoms recurring hours after initial resolution 6, 4, 2

Diagnostic Testing

Obtain serum tryptase levels when clinical diagnosis is uncertain:

• Initial sample as soon as feasible after resuscitation starts 4, 7
• Subsequent samples at 1-2 hours and 24 hours after symptom onset 4

Allergist-immunologist will coordinate:

• Immediate hypersensitivity skin testing 1
• In vitro specific IgE tests 1
• Challenge tests when indicated (including exercise challenges) 1

Mandatory Discharge Requirements

All patients treated for anaphylaxis must receive before discharge: 6, 4

1. Two epinephrine auto-injectors with proper dosing and training on self-injection technique 6, 4
2. Written anaphylaxis emergency action plan detailing symptom recognition and step-by-step treatment 6, 4
3. Instructions to carry auto-injectors at all times and self-inject at first sign of symptom recurrence, then immediately call ambulance 6
4. Mandatory referral to allergist-immunologist 6, 4

Consider continuation of adjunctive treatment for 2-3 days post-discharge (H1 antihistamine, H2 antihistamine, corticosteroid), though these do not reliably prevent biphasic reactions 6, 3

Specialist Referral

Refer all patients with suspected or confirmed allergic conditions to allergist-immunologist 1, 6

Allergist-immunologists provide:

• Detailed allergy history and comprehensive diagnostic testing 1
• Coordination of laboratory and allergy testing 1
• Evaluation of benefits and risks of therapeutic options 1
• Counseling on avoidance measures 1
• Development of long-term management strategies 6, 4
• Identification of specific triggers through properly timed serum tryptase levels if diagnosis uncertain 6

Specific referral indications:

• Anaphylaxis without obvious or previously defined trigger 1
• Food-induced anaphylaxis 1
• Exercise-induced or food-dependent exercise-induced anaphylaxis 1
• Drug-induced anaphylaxis 1
• Suspected allergic bronchopulmonary aspergillosis 1

Pharmacologic Therapy Options (Allergist-Directed)

Based on identified trigger:

• Immunotherapy for Hymenoptera venom allergy (90% success rate) 1, 8
• Avoidance strategies for food allergens 1
• Desensitization protocols for drug allergies (e.g., penicillin) 1
• Graded challenge for local anesthetics or aspirin 1
• Premedication protocols for radiocontrast media 1

Consider discontinuation of ACE inhibitors and beta-blockers in patients with anaphylaxis history 1

Patient Education

Provide printed information about anaphylaxis and its treatment 6

Emphasize intensive education on:

• Specific allergen avoidance based on identified triggers 6
• Risk for repeat episodes in the future 6
• Importance of subsequent testing to determine and verify triggers 6
• Proper epinephrine auto-injector technique 6, 4

High-Risk Patient Identification

Patients at highest risk for fatal anaphylaxis:

• Adolescents and young adults 6
• Patients with concomitant asthma 6, 7
• Previous anaphylaxis history 6
• Known allergy to peanuts, tree nuts, fish, or crustacean shellfish 6
• Cardiovascular disease 6
• Those on beta-blockers 6, 7
• Elderly patients 6
• Mast cell disorders 7

Critical Pitfalls to Avoid

Never discharge patients without epinephrine auto-injectors and proper training—this is associated with increased mortality 6

Do not rely on antihistamines or corticosteroids alone—these are adjunctive only and do not prevent biphasic reactions reliably 6, 3

Avoid premature discharge—observation periods must account for biphasic reaction risk, which can occur up to 72 hours after initial event 6

Do not delay epinephrine administration while administering antihistamines or corticosteroids 4, 5

Absence of cutaneous symptoms does not rule out anaphylaxis—proceed with treatment if other criteria met 1, 2