Water Temperature for Acute Urticaria
For patients with acute urticaria, use lukewarm or cool water for bathing and showering, avoiding hot water entirely, as heat is a known trigger that can worsen whealing and pruritus. 1
Why Avoid Hot Water
- Hot water acts as a nonspecific aggravating factor that can trigger or worsen urticaria through direct mast cell degranulation and histamine release 1
- Water temperatures above 40°C cause lipid fluidization in the stratum corneum, leading to increased skin permeability and potential irritation 2
- In patients with combined physical urticarias, hot water (41°C) can induce systemic histamine release and symptoms including generalized wheals, pruritus, palpitations, and headaches 3
Recommended Bathing Practices
- Use lukewarm or cool water exclusively when bathing or showering to minimize mast cell activation 2, 1
- The CDC and dermatology guidelines recommend cold or lukewarm water specifically because water temperature does not affect microbial removal, making hot water unnecessary 2
- Limit bathing duration to 10-15 minutes to prevent excessive skin drying 4
- Use fragrance-free, neutral pH hypoallergenic soaps or non-soap cleansers sparingly, as regular soaps can act as irritants 2, 5
Additional Trigger Avoidance
- Minimize other aggravating factors including overheating from any source, tight clothing, NSAIDs, and alcohol 2, 1
- Apply cooling antipruritic lotions such as calamine or 1% menthol in aqueous cream for symptomatic relief 2
- Pat skin dry gently after bathing rather than rubbing vigorously 2
Important Clinical Caveat
Do not confuse this recommendation with cholinergic urticaria with hypohidrosis/anhidrosis (CUHA), which is a distinct subtype where paradoxically hot bath therapy (40-43°C for 30-60 minutes) is used as a specific desensitization treatment. 6 This specialized approach applies only to CUHA patients under medical supervision and should never be applied to typical acute urticaria, where hot water remains contraindicated.
First-Line Treatment Alongside Water Temperature Management
- Second-generation H1-antihistamines (such as cetirizine, loratadine, or fexofenadine) are the cornerstone of acute urticaria treatment 2, 1
- Acute urticaria is self-limited in all cases, typically resolving within days to 3 weeks maximum 7
- For severe cases unresponsive to antihistamines, short-course oral corticosteroids (prednisolone 50 mg/day for 3 days) achieve complete remission within 3 days in 93.8% of patients 7