Hospital-Based Tap Water Iontophoresis for Primary Focal Hyperhidrosis: A Real-World Analysis of Treatment Adherence, Efficacy, and Relapse

<b>Background:</b> Tap water iontophoresis (TWI) is a well-established second-line treatment for primary focal hyperhidrosis. While its efficacy is proven, data regarding the correlation between session frequency and clinical response, as well as long-term adherence in hospital-based settings, remain limited. <b>Objective:</b> We aimed to evaluate the efficacy and safety of hospital-based TWI and to analyze the relationship between the number of treatment sessions and clinical outcomes. <b>Methods:</b> This retrospective study included 92 patients with primary focal hyperhidrosis treated with TWI. Disease severity was assessed using the Hyperhidrosis Disease Severity Scale (HDSS). Clinical response was categorized as "Excellent" (≥2-point HDSS reduction), "Good" (1-point reduction), or "No Response." Relapse rates and reasons for treatment discontinuation were analyzed over a 6-month follow-up period. <b>Results:</b> The overall objective response rate was 65.2% (46.7% Excellent, 18.5% Good). A significant positive correlation was found between the total number of treatment sessions and the degree of clinical response (r = 0.401, <i>p</i> < 0.001). Patients achieving an "Excellent" response completed a significantly higher median number of sessions compared to non-responders (<i>p</i> = 0.001). However, among responders, the relapse rate was 85% within six months. Logistical difficulties were the most common reason for treatment discontinuation (17.5%). No compensatory hyperhidrosis or severe adverse events were observed. <b>Conclusions:</b> Hospital-based TWI is a safe and highly effective induction therapy, with success rates closely linked to the number of completed sessions. However, the high relapse rate and logistical barriers to adherence suggest that hospital-based protocols should serve primarily as a bridge to home-based maintenance therapy to ensure sustained long-term remission.