Introduction

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disorder affecting 15–20% of children and 1–10% of adults in the United States and worldwide¹–⁴. Deficiencies in the epidermal barrier and dysfunction of the immune system contribute to AD pathogenesis, resulting in the characteristic signs and symptoms of AD (e.g. xerosis and pruritus) and predisposing patients to cutaneous infections. AD is associated with a higher prevalence of epidermal S. aureus colonization compared with healthy controls (>70% vs. 10–20%)^{5, 6}. In particular, AD severity is correlated with epidermal S. aureus density; AD flares are associated with cutaneous S. aureus infection, and AD exacerbations may be induced by S. aureus overgrowth even without frank infection^{5, 7, 8}. Given the importance of S. aureus colonization and microbiome in AD, anti-bacterial treatments have been considered for managing AD⁹. However, the prolonged use of traditional topical and/or systemic antibiotics to suppress recolonization may be impractical given potential concerns about increased antibiotic resistance from long-term antibiotic use^{10, 11}.

Bleach (sodium hypochlorite, NaOCl) baths are an inexpensive, widely accessible, alternative antibiotic treatment that may not worsen antibiotic resistance¹². Bleach baths demonstrate in vitro and in vivo antibacterial and anti-biofilm properties^{13, 14}, are associated with few adverse events, demonstrate no harmful effects on stratum corneum hydration, transepidermal water loss (TEWL), and epidermal pH¹⁵, and do not appear to cause antibiotic resistance¹². As such, dilute bleach baths have been proposed to suppress epidermal S. aureus load and ultimately reduce AD severity. Huang et al.⁹ first conducted a randomized controlled trial (RCT) of bleach baths as a treatment for moderate-to-severe AD with promising results. However, subsequent RCT yielded conflicting results. Nevertheless, bleach baths are recommended in multiple clinical practice guidelines¹⁶–¹⁹. We performed a systematic review in order to determine the whether bleach baths are consistently effective in improving the severity of AD.

Methods

Results

Study selection

We identified 124 non-duplicate citations via our initial search strategy. The title and abstract review excluded 116 citations, while the full-text review excluded an additional 3 citations. We included 5 studies^{9, 20}–²³ in this systematic review as outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses²⁴ flow diagram (Fig. 1).

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Figure 1

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram

Pooled analysis of efficacy

EASI and BSA assessments at 4-weeks were the only end-points and time-points in common across at least 3 studies (Fig. 2A, B). In pooled analyses, the mean ± std. dev. EASI and BSA decreased at 4 weeks vs. baseline in both the bleach (EASI: 11.0±7.8 vs. 24.9±25.3; BSA: 42.8%±12.7% vs. 49.8%±18.1%) and water bath (EASI: 14.2±7.7 vs. 25.2±12.3; BSA: 41.1%±18.1% vs. 45.6%±17.9%) groups, respectively (Fig. 2C, D). There were no significant differences observed between bleach vs. water baths at 4 weeks vs. baseline for EASI (I²=98%; random effect regression model, P=0.16) or BSA (I²=96%; P=0.36).a

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Figure 2

EASI and BSA for bleach vs. water baths at 4 weeks compared with baseline

Mean (A) EASI and (B) BSA of bleach baths (solid lines) and water baths (dashed lines) are presented for individual studies. Pooled mean ± std. dev. (C) EASI and (D) BSA of bleach baths (solid lines) and water baths (dashed lines) are presented for 3 combined studies.

Discussion

This systematic review found that bleach baths/cleansers and water baths alone significantly reduced AD severity. However, water baths were as effective as bleach baths at 4 weeks in pooled analyses, with only one study of efficacy at later time-points. There were no differences of S. aureus density in patients treated with bleach vs. water baths. Together, the results suggest that much of the efficacy of bleach baths at reducing AD severity is attributable to water baths and less the bleach per se.

Bleach baths are compound interventions with multiple steps: water bath, exposure to bleach during the bath, and application of emollients and/or topical anti-inflammatory agents after the bath. Each of these 3 steps may be effective at reducing AD severity. Water baths alone may hydrate and sooth the skin, and can wash away scale and serum-crust. The bleach may have anti-staphylococcal and other disinfecting properties. Although, the results of the present study indicate that water baths were similarly effective as bleach baths at disinfecting the skin. Application of emollients and/or topical anti-inflammatories after the bath (referred to as prehydration, “soak and seal”, or “soak and smear”) may seal moisture in the stratum corneum, increased permeability, and enhance drug absorption^{25, 26}. Previous studies showed good efficacy for soak and smears²⁷–²⁹, though a recent RCT found no greater efficacy than TCS on dry skin³⁰. Water bath alone or the soak and smear regimen may be effective without the addition of bleach.

Bleach baths are commonly recommended because they are inexpensive, relatively safe and easily accessible. Upon reviewing the results of this study, clinicians might wonder what difference does it make whether bleach baths or water baths alone should be recommended? However, there are several important considerations. Exposure to dilute bleach can result in stinging, burning and transient worsening of itch. Ocular exposure to bleach can be particularly uncomfortable and hinders prehydration of the face. There is additional cost and time spent acquiring bleach, albeit fairly minimal. Bleach may stain towels, linens and/or clothing. Bleach baths emit caustic fumes. One of the authors (JS) had two patients with reported asthma exacerbations due to inhalation of fumes from bleach baths. It is important to recognize that water baths alone might accomplish similar efficacy as bleach baths without these additional concerns.

Comparison of study results is hindered by differences of inclusion criteria, patient phenotype, interventions, and outcome measures across studies. Different diagnostic criteria and severity assessments were used to recruit patients, which may result in study populations with differing phenotype^{31, 32}. Active cutaneous infections were used as inclusion criteria in half of studies and exclusion criteria in the other half. Blinding protocols and success varied across studies. Only half of RCT exclusively compared bleach to water baths without other concurrent interventions. One study concurrently administered mupirocin and cephalexin, which may be confounding factors⁹. Different severity measures were used to evaluate efficacy outcomes across studies, showing inconsistent efficacy between studies and within individual studies. Differences in bathing protocol may have impacted study results. Bathing is a multicomponent process comprised of soap, water and bleach exposure factors (e.g. duration, frequency, temperature, etc.), and aftercare such as drying, emollients and topical medications. There was no documented efforts to standardize most of these variables, except frequency and duration of baths in all studies and soap-use in one study. Only one study standardized TCS use, and no studies coordinated the use of TCS and emollient with bath regimens. As the principal intervention of interest, bathing protocol should be thoroughly documented, standardized, and isolated from the effect of confounding factors such as additional concurrent interventions. Future studies are needed that properly address these concerns.

Current primary care provider recommendations advocate for infrequent bathing in AD³³. However, the results of this systematic review indicate that regular bathing and emollient use is an effective treatment for AD and better than infrequent bathing. These results provide evidence to support the AAD guidelines’ recommendation for regular bathing in the care of AD³⁴. The AAD guidelines also recommend use of dilute bleach baths in patients with frequent bacterial infections³⁴. Interestingly, bleach baths were not more effective than water baths in studies that recruited patients with clinically infected AD. It may be that water baths alone can reduce risk of bacterial infection in AD patients and future studies are needed to elucidate this point.

The studies included in this systematic review showed no significant difference between bleach and water bath interventions in reducing S. aureus epidermal colonization or density. These findings are unexpected as AD exacerbations are correlated with epidermal S. aureus density and bleach baths are hypothesized to improve AD severity via their antibacterial properties^{14, 35}. In contrast, bleach baths and mupirocin were found to eradicate S. aureus colonization in an RCT of non-AD patients with community acquired staphylococcal skin/soft tissue infections compared to controls at 1 and 4 months (63% vs. 38% and 71% vs. 48%, respectively)³⁶. A recent Cochrane review concluded there are no discernable benefits of anti-staphylococcal interventions in reducing S. aureus density in AD patients compared to anti-inflammatory medications³⁷, which is consistent with the results of our study.

Our study has several strengths including the use of a comprehensive search strategy and examination of studies from all countries and languages. Pooled analysis was performed at 4 weeks using random-effects regression models to address issues of heterogeneity. This pooled analysis provided novel insight by demonstrating that water baths were also effective at reducing AD severity. However, there are several limitations to our study, including a small number of studies, small study populations, short follow-up durations, and each were conducted at a single center. Moreover, there was a lack of uniformity with respect to AD diagnostic and inclusion criteria, demographics, study interventions, and outcome measures across studies, which require cautious interpretation.

In conclusion, while bleach baths are effective in reducing AD severity, they do not appear to be more effective than water bath alone. However, there are a number of limitations with the currently available studies. Future, larger-scale RCT are needed that address these limitations.

Abbreviations used

Footnotes

References