Bathing Frequency and Eczema Severity: Analysis of the Eczema Bathing Citizen Science Randomized Controlled Trial

Highlights

• The Eczema Bathing RCT found no statistically significant difference in eczema severity (measured by POEM) between participants who bathed/showered daily versus those who bathed/showered weekly.
• The adjusted difference in mean POEM score over the 4-week study period was -0.4 (95% CI -1.3 to 0.4; P = 0.30), indicating equivalence in clinical outcomes regardless of frequency.
• This trial represents a milestone in ‘citizen science,’ utilizing an online, pragmatic design to address a high-priority patient concern that had previously lacked high-quality evidence.
• Clinicians can confidently advise patients that bathing frequency may be guided by personal preference and lifestyle rather than a strict therapeutic mandate.

Background

Atopic dermatitis (eczema) is a chronic inflammatory skin condition characterized by a defective skin barrier, intense pruritus, and a relapsing-remitting course. For decades, one of the most persistent and debated questions in dermatology has been: “How often should I wash?”

Traditionally, two conflicting philosophies have dominated clinical advice. The “frequent bathing” school of thought—often termed the “soak and smear” technique—suggests that daily bathing or showering followed by immediate application of emollients can hydrate the stratum corneum and remove allergens, bacteria, and irritants from the skin surface. Conversely, the “infrequent bathing” school argues that excessive exposure to water and detergents can further deplete natural moisturizing factors (NMFs) and lipids, leading to xerosis and exacerbation of inflammation.

Despite the clinical relevance, randomized controlled trials (RCTs) specifically addressing bathing frequency have been scarce, often small in scale, or conducted in controlled inpatient settings that do not reflect real-world behaviors. The Eczema Bathing online RCT was designed to fill this evidence gap using a pragmatic, participant-led approach to provide clear guidance for the millions of people living with this condition.

Key Content

Methodological Innovation: The Citizen Science Approach

The study employed a pragmatic, two-arm, parallel-group superiority RCT design. A notable aspect of this trial was its “citizen science” framework, which leveraged online recruitment and data collection to include 438 participants across the UK. This methodology allowed for a diverse cohort (ages 1 and up) and ensured that the trial addressed questions generated by the patient community.

Participants were randomized (1:1) to either:

• Weekly Bathing: Bathing or showering only once or twice per week.
• Daily Bathing: Bathing or showering at least six times per week.

Randomization was balanced using minimization based on baseline eczema severity (POEM), age, and usual bathing habits. The primary outcome was measured using the Patient-Orientated Eczema Measure (POEM), a validated 7-item tool that captures symptoms such as itching, sleep loss, and skin dryness over the preceding week.

Clinical Outcomes and Statistical Significance

The analysis included 388 participants who provided follow-up data (89% of the daily group and 88% of the weekly group).

Primary Outcome (POEM Scores):
At baseline, mean POEM scores were balanced (14.5 for the daily group; 14.9 for the weekly group), representing moderate-to-severe eczema. Over the 4-week intervention period, both groups experienced a slight improvement in symptoms.

At the end of week 4, the mean POEM scores were:

• Daily Bathing Group: 11.6 (SD 6.5)
• Weekly Bathing Group: 10.6 (SD 7.2)

The adjusted difference in mean POEM score over the 4 weeks was -0.4 (95% CI -1.3 to 0.4; P = 0.30). Since the confidence interval crossed the null and did not meet the threshold for a clinically important difference (typically 2-3 points on the POEM scale), the study concluded there was no evidence of superiority for either regimen.

Process Evaluation and Adherence

A qualitative process evaluation conducted alongside the trial highlighted the practicalities of these interventions. Participants in the weekly bathing group reported challenges related to lifestyle habits, hygiene concerns in summer months, and the social stigma of not bathing daily. Conversely, some participants in the daily group found the routine time-consuming. Despite these barriers, no serious unintended effects or harms were reported, confirming the safety of both approaches when performed with standard emollient care.

Expert Commentary

Mechanistic Insights into the Skin Barrier

From a physiological perspective, these results suggest that the skin’s compensatory mechanisms and the use of emollients likely buffer the effects of varying water exposure. While water can temporarily hydrate the skin, it also triggers evaporation-induced dryness if not occluded. The lack of difference between weekly and daily bathing suggests that for most patients, the frequency of washing is secondary to the quality of skin care (e.g., soap substitutes, emollient application) and the underlying immunological drivers of the disease.

Clinical Applicability and Guidelines

Current international guidelines, such as those from the American Academy of Dermatology (AAD) and the European Academy of Dermatology and Venereology (EADV), have historically offered vague recommendations on bathing frequency, often suggesting once-daily bathing with short duration and lukewarm water. The results of the Bradshaw et al. trial provide much-needed empirical support for a more flexible approach.

Clinicians should shift the conversation from a “one-size-fits-all” frequency to a patient-centered model. For instance, a patient who enjoys daily showers for mental well-being or post-exercise hygiene should be encouraged to continue, provided they use soap-free cleansers. Similarly, a parent struggling to bathe a child with eczema every night can be reassured that reducing frequency to twice a week is unlikely to worsen the child’s skin condition.

Limitations

While the trial was well-powered, it was unblinded (as is common in behavioral interventions) and relied on self-reported data. The 4-week duration, though sufficient to capture symptom changes, may not reflect long-term seasonal variations or the impact of bathing frequency on secondary infections like Staphylococcus aureus colonization.

Conclusion

The Eczema Bathing RCT provides robust evidence that bathing frequency—whether once or twice a week versus daily—does not significantly alter the clinical course of eczema over a month. These findings empower patients with the freedom to choose a hygiene routine that fits their lifestyle, sensory preferences, and family needs. Future research should investigate whether specific bathing additives (such as oils or colloidal oatmeal) or water hardness interact with bathing frequency to influence long-term skin barrier health.

References

• Bradshaw L, Howells LM, Muller I, et al. Weekly versus daily bathing for people with eczema: results of the Eczema Bathing online randomized controlled trial. Br J Dermatol. 2026;194(3):450-460. doi: 10.1093/bjd/ljaf417. PMID: 41208015.
• Charman CR, Venn AJ, Williams HC. The patient-oriented eczema measure: development and initial validation of a new tool for monitoring atopic eczema. Arch Dermatol. 2004;140(12):1513-1519. PMID: 15611430.
• Eichenfield LF, Tom WL, Berger TG, et al. Guidelines of care for the management of atopic dermatitis: section 2. Management and treatment of atopic dermatitis with topical therapies. J Am Acad Dermatol. 2014;71(1):116-132. PMID: 24813302.