What is the treatment for a patient with allergic contact urticaria?

Treatment of Allergic Contact Urticaria

For allergic contact urticaria, immediately initiate second-generation H1-antihistamines as first-line treatment, ensure patients at risk of anaphylaxis carry an epinephrine auto-injector, and prioritize identification and avoidance of the triggering allergen through appropriate testing. 1

Immediate Management and Risk Stratification

Assess Anaphylaxis Risk

• Evaluate for systemic symptoms including flushing, syncope, tachycardia, hypotension, bronchospasm, laryngospasm, or gastrointestinal symptoms, as these indicate potential anaphylaxis requiring immediate epinephrine administration 2
• Patients with immunologic contact urticaria (I-CoU) are at risk for anaphylaxis and must be equipped with an adrenaline auto-injector and wear a medical alert bracelet 1
• Epinephrine acts on alpha-adrenergic receptors to reduce vascular permeability and on beta-adrenergic receptors to relieve bronchospasm, while also alleviating pruritus, urticaria, and angioedema 2

Distinguish Type of Contact Urticaria

• Non-immunologic contact urticaria (NI-CoU) typically presents with mild, localized reactions that clear within hours and is triggered by low molecular weight chemicals 1, 3
• Immunologic contact urticaria (I-CoU) involves IgE-mediated hypersensitivity to proteins or chemicals, occurs most commonly in atopic individuals, and may progress to systemic symptoms 1, 3
• Document whether individual wheals last 2-24 hours (typical urticaria) versus >24 hours (suggests urticarial vasculitis requiring different management) 4

First-Line Pharmacologic Treatment

Second-Generation H1-Antihistamines

• Start with standard-dose second-generation H1-antihistamines (cetirizine, fexofenadine, loratadine, desloratadine, or levocetirizine) as the first-line treatment for I-CoU 5, 4, 1
• These agents are preferred over first-generation antihistamines due to improved safety profile and reduced sedation 5, 6
• If inadequate control after 2-4 weeks, increase the dose up to 4 times the standard daily dose 5, 4

Adjunctive Pharmacotherapy

• Consider adding H2-antihistamines, leukotriene receptor antagonists, or brief corticosteroid bursts as adjunctive treatment if symptoms persist 6, 7
• Avoid long-term oral corticosteroids as they lead to significant morbidity (hypertension, hyperglycemia, osteoporosis, gastric ulcers) without addressing underlying disease 8

Diagnostic Approach and Allergen Identification

Skin Testing Strategy

• Perform skin prick testing or use testing to confirm immunologic contact urticaria, as these simple investigations can identify specific IgE-mediated reactions 1, 3
• Antihistamines do not need to be avoided unless specifically testing for urticaria or contact urticarial reactions 9
• Consider measurement of specific IgE for suspected allergens 3

Patch Testing Considerations

• While patch testing is the gold standard for allergic contact dermatitis, it is not routinely indicated for contact urticaria as it tests for delayed (type IV) hypersensitivity rather than immediate (type I) reactions 9
• Patch testing showed no relationship between avoidance of contact allergens and improvement in chronic urticaria in one study 10
• However, patients with I-CoU may also develop protein contact dermatitis, which would benefit from patch testing 9, 1

Trigger Avoidance and Prevention

Primary Prevention Strategy

• Identification and complete avoidance of the triggering allergen is the cornerstone of management 1, 6, 7
• Common triggers include natural rubber latex (most important occupational cause), foods, cosmetics, medicaments, and animal or vegetable proteins 1, 3
• Provide clear communication about relevant allergens to allow patients to identify, avoid, or substitute the causative agents 9

Occupational Considerations

• For occupational exposures, workplace assessment may be necessary to identify all potential allergens and implement appropriate protective measures 9
• Glove selection is critical for hand protection, with specific glove types required based on the chemical involved and exposure duration 9

Advanced Treatment for Refractory Cases

Second-Line Therapy

• If symptoms remain inadequately controlled despite up-dosed antihistamines, add omalizumab 300 mg subcutaneously every 4 weeks 5, 8, 1
• Omalizumab (anti-IgE therapy) may benefit severe cases of I-CoU, particularly those at risk of anaphylaxis 1
• Allow up to 6 months for patients to demonstrate response to omalizumab before considering alternative therapies 5

Third-Line Options

• If inadequate control persists with omalizumab, consider adding cyclosporine (up to 5 mg/kg body weight) to the antihistamine regimen 5
• Monitor blood pressure and renal function every 6 weeks while on cyclosporine 5

Monitoring and Follow-Up

Disease Control Assessment

• Use the Urticaria Control Test (UCT) to formally assess disease control, with a score ≥12 indicating well-controlled disease 8, 4
• Once complete symptom control is achieved, maintain the effective dose for at least 3 consecutive months before considering step-down 5
• When stepping down, reduce the daily dose by no more than 1 tablet per month 5

Critical Pitfalls to Avoid

• Do not delay effective therapy while continuing ineffective high-dose antihistamines beyond 4-fold standard dosing 8
• Do not confuse contact urticaria with allergic contact dermatitis—they represent different immunologic mechanisms (type I versus type IV hypersensitivity) requiring different diagnostic approaches 1, 3
• Do not overlook anaphylaxis risk in patients with I-CoU, as failure to provide epinephrine auto-injectors can result in preventable mortality 1
• Avoid common aggravating factors including NSAIDs, aspirin, codeine, alcohol, overheating, and stress 4