Does daily bathing or showering worsen atopic dermatitis severity? A systematic review and meta-analysis

The optimal frequency of water bathing/showering in atopic dermatitis (AD) is unknown. We sought to determine the efficacy of different bathing/showering frequencies at improving AD severity. A systematic review and meta-analysis was performed of studies evaluating the clinical efficacy of bathing/showering regimen in AD. MEDLINE, EMBASE, SCOPUS, LILACS, Cochrane, China National Knowledge Infrastructure, Taiwan electronic periodical services and CiNii were searched. Two authors independently performed title/abstract and full-text review and data extraction. All 13 included studies were prospective and demonstrated numerically reduced AD severity in patients treated with a water bathing/showering regimen in ≥ 1 time-point compared with baseline. In random-effects regression models, baths/showers ≥ 7 vs. < 7 times per week were not associated with significant differences of Cohen's D scores for eczema area and severity index (n = 5 studies; least-square means: 1.34 vs. 0.90; P = 0.45; I² = 91.8), Scoring AD (n = 5 studies; 0.73 vs. 0.41; P = 0.13; I² = 97.4) or body surface area (n = 4 studies; 0.45 vs. 0.28; P = 0.17; I² = 93.4). Similar results were observed in sensitivity analyses by study design, quality, use of emollients, and use of topical corticosteroids. No publication bias was detected by Egger regression (P ≥ 0.26) or Begg rank (P ≥ 0.19) tests. Three studies were included in the qualitative analysis, which found that bathing/showering ≥ 7 resulted in significant improvement of Investigator Global Assessments, extent of skin lesions and itch caused by AD. In conclusion, the optimal frequency of water bathing/showering in AD remains unclear. Daily showers/baths were not associated with worse severity, and should be permitted in AD. Larger scale, well-designed RCT are still needed to determine the optimal bathing parameters.