What is the treatment for a patient experiencing hives due to overheating?

Treatment of Hives Due to Overheating

For hives triggered by overheating, start with second-generation non-sedating H1 antihistamines (cetirizine, fexofenadine, loratadine, or desloratadine) at standard doses, and if inadequate after 2-4 weeks, increase up to 4 times the standard dose. 1, 2, 3

Diagnostic Clarification

This presentation most likely represents cholinergic urticaria or heat urticaria, both physical urticarias triggered by elevated core body temperature. 4, 5, 6

• Cholinergic urticaria produces small (1-3 mm), punctate, intensely pruritic wheals with erythematous flaring when core body temperature increases during exercise, hot showers, or emotional stress 4, 6
• Heat urticaria produces larger, well-demarcated wheals appearing soon after direct heat exposure (typically above 44°C threshold), and can be localized to the exposed area or generalized 5
• Both conditions differ from exercise-induced anaphylaxis, which involves systemic symptoms like wheezing, vascular collapse, and requires both exercise and often food ingestion 4

First-Line Pharmacologic Management

Start with a single second-generation H1 antihistamine at standard dosing for 2-4 weeks: 1, 2, 3

• Cetirizine 10 mg daily
• Fexofenadine 180 mg daily
• Loratadine 10 mg daily
• Desloratadine 5 mg daily
• Levocetirizine 5 mg daily

Trial at least two different non-sedating antihistamines if the first is ineffective, as individual responses vary significantly. 2, 3

Dose Escalation for Inadequate Response

If standard dosing provides inadequate control after 2-4 weeks, increase the antihistamine dose up to 4 times the standard dose. 1, 2, 3 Over 40% of patients with ordinary urticaria show good response to antihistamines alone, but many require higher doses. 1

Add a first-generation sedating antihistamine at night (hydroxyzine 10-50 mg or chlorphenamine 4-12 mg) for additional symptom control and to help with sleep. 2, 3

Adjunctive Therapies

Add H2-antihistamines (ranitidine or famotidine) for resistant cases, which may provide better control than H1 antihistamines alone. 2, 3

Consider adding leukotriene receptor antagonists (montelukast) for refractory cases. 3

Critical Medications to Avoid

Avoid NSAIDs and aspirin, as they inhibit cyclooxygenase and can exacerbate urticaria through leukotriene formation and histamine release. 1, 2, 3

Behavioral and Environmental Modifications

Identify and minimize aggravating factors including overheating, stress, and alcohol. 3

For cholinergic urticaria specifically, early recognition of prodromal symptoms (pruritus, cutaneous warmth, flushing) is critical—discontinue heat exposure or exercise immediately at the earliest symptom. 4

Patients should be accompanied during exercise by someone aware of their condition and capable of providing emergency assistance. 4

Advanced Therapies for Refractory Cases

Omalizumab 300 mg subcutaneously every 4 weeks is recommended for chronic urticaria unresponsive to high-dose antihistamines, with up to 6 months allowed for response. 2, 3, 5

Cyclosporine 4 mg/kg daily for up to 2 months is effective in approximately 65-70% of patients who fail omalizumab. 3

Novel Therapeutic Approach

Heat desensitization through hot bath therapy (40-43°C for 30-60 minutes daily for 3-7 days) can be effective, particularly for cholinergic urticaria with hypohidrosis. 7, 5 In one study, this improved pain in 43%, urticaria in 50%, and anhidrosis in 63% of patients without severe adverse events. 7

Emergency Management

Administer intramuscular epinephrine 0.5 mL of 1:1000 immediately if systemic symptoms develop (wheezing, hypotension, laryngeal edema, oxygen desaturation, or cardiovascular collapse). 4, 3 This distinguishes progression to exercise-induced anaphylaxis, which requires the same emergency management as anaphylaxis from other causes. 4

Role of Corticosteroids

Restrict oral corticosteroids to short courses only for severe acute episodes, due to cumulative toxicity including hypertension, hyperglycemia, osteoporosis, and gastric complications. 2, 3 Prophylactic antihistamines are generally more effective than steroids for preventing recurrent episodes. 4

Common Pitfalls

• Do not rely on antihistamines alone to abort an acute anaphylactic attack—early epinephrine administration is essential if systemic symptoms develop 4
• Do not continue NSAIDs or aspirin, as cross-reactions are common and related to potency of cyclooxygenase inhibition 2
• Do not use inadequate antihistamine dosing—many patients require higher than standard doses for symptom control 2, 3

Prognosis

Heat urticaria is typically a long-lasting disease with overall duration at diagnosis of approximately 2 years. 5 About 50% of patients with chronic urticaria presenting with wheals alone will be clear by 6 months. 3