The effect of water hardness on atopic eczema, skin barrier function: A systematic review, meta‐analysis

Abstract

Background Hard domestic water has been reported to worsen atopic eczema (AE) and may contribute to its development in early life. Objective To review the literature on the relationship between the effect of water hardness (high calcium carbonate; CaCO3) on (a) the risk of developing AE, (b) the treatment of existing AE and (c) skin barrier function in human and animal studies. Design , data sources and eligibility criteria We systematically searched databases (MEDLINE, Embase, Cochrane CENTRAL, GREAT and Web of Science) from inception until 30/6/2020. Human and animal observational and experimental studies were included. The primary outcomes were risk of AE and skin barrier function. Studies were meta‐analysed using a random effects model. Evidence certainty was evaluated using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. Results Sixteen studies were included. Pooled observational data from seven studies on 385,901 participants identified increased odds of AE in children exposed to harder versus softer water (odds ratio 1.28, 95% CI 1.09, 1.50; GRADE certainty: very low). Two mechanistic studies in humans reported higher deposition of the detergent sodium lauryl sulphate in those exposed to harder versus softer water. Two randomized controlled trials comparing water softeners with standard care did not show a significant difference in objective AE severity with softened water (standardized mean difference 0.06 standard deviations higher, 95% CI 0.16 lower to 0.27 higher; GRADE certainty: moderate). Conclusions & Clinical Relevance There was a positive association between living in a hard water (range: 76 to > 350 mg/L CaCO3) area and AE in children. There is no evidence that domestic water softeners improve objective disease severity in established AE. There may be a role of water hardness in the initiation of skin inflammation in early life, but there is a need for further longitudinal and interventional studies.

Randomized controlled pilot trial with ion‐exchange water softeners to prevent eczema (SOFTER trial)

“…19 To date, there are no studies examining the role of water softeners in the prevention of eczema. 20 The overall rationale was that by installing a domestic water softener around the time of birth, the infant would be exposed to softened water rather than hard water for bathing and that this would be less irritating to the skin than hard water and so associated with a lower risk of eczema development. Such a study would require a large number of participants and before embarking on this it was important to determine whether the planned trial recruitment and assessment procedures are possible and workable, or whether they required adapting or changing.…”

“…After 6 weeks, no statistically significant differences in eczema area severity index (EASI) or transepidermal water loss (TEWL) were observed between the groups, although there was a statistically significant improvement in pruritus as measured by visual analogue score 19 . To date, there are no studies examining the role of water softeners in the prevention of eczema 20 …”

Patterns of Atopic Eczema Disease Activity From Birth Through Midlife in 2 British Birth Cohorts

“…Environmental factors including temperature and humidity, water hardness, pollution levels, and the environmental microbiome have been linked to AD and may vary geographically and temporally. 22,[37][38][39] Future research should examine the role of environmental factors on patterns and persistence of atopic eczema over time.…”

Evidence Synthesis in Allergy – A call for submissions

“…Our trusted evidence mission means that we are particularly interested in publishing high‐quality evidence synthesis work in allergy. Historically, our evidence synthesis publications have mainly been simple systematic reviews of intervention trials or observational studies 1–9 . However, we published our journal's first individual participant data meta‐analysis earlier this year 10 and are interested in receiving submissions of other more sophisticated approaches to evidence synthesis, including network meta‐analyses, systematic reviews of prognostic or diagnostic studies, rapid reviews or living systematic reviews.…”

“…Historically, our evidence synthesis publications have mainly been simple systematic reviews of intervention trials or observational studies. [1][2][3][4][5][6][7][8][9] However, we published our journal's first individual participant data meta-analysis earlier this year 10 and are interested in receiving submissions of other more sophisticated approaches to evidence synthesis, including network meta-analyses, systematic reviews of prognostic or diagnostic studies, rapid reviews or living systematic reviews. We are also interested in receiving manuscripts that describe other types of meta-research work, for example, work identifying patterns of research prioritization, conduct, reporting and dissemination relevant to the field of allergy.…”