Association between domestic water hardness, chlorine, and atopic dermatitis risk in early life: A population-based cross-sectional study

Abstract

Background: Domestic water hardness and chlorine have been suggested as important risk factors for atopic dermatitis (AD). Objective: We sought to examine the link between domestic water calcium carbonate (CaCO 3) and chlorine concentrations, skin barrier dysfunction (increased transepidermal water loss), and AD in infancy. Methods: We recruited 1303 three-month-old infants from the general population and gathered data on domestic water CaCO 3 (in milligrams per liter) and chlorine (Cl 2 ; in milligrams per liter) concentrations from local water suppliers. At enrollment, infants were examined for AD and screened for filaggrin (FLG) skin barrier gene mutation status. Transepidermal water loss was measured on unaffected forearm skin. Results: CaCO 3 and chlorine levels were strongly correlated. A hybrid variable of greater than and less than median levels of CaCO 3 and total chlorine was constructed: a baseline group of low CaCO 3 /low total chlorine (CaL/ClL), high CaCO 3 /low total chlorine (CaH/ClL), low CaCO 3 /high total chlorine (CaL/ClH) and high CaCO 3 /high total chlorine (CaH/ClH). Visible AD was more common in all 3 groups versus the baseline group: adjusted odds ratio (AOR) of 1.87 (95% CI, 1.25-2.80; P 5 .002) for the CaH/ClL group, AOR of 1.46 (95% CI, 0.97-2.21; P 5 .07) for the CaL/ClH, and AOR of 1.61 (95% CI, 1.09-2.38; P 5 .02) for the CaH/ClH group. The effect estimates were greater in children carrying FLG mutations, but formal interaction testing between water quality groups and filaggrin status was not statistically significant. Conclusions: High domestic water CaCO 3 levels are associated with an increased risk of AD in infancy. The influence of increased total chlorine levels remains uncertain. An intervention trial is required to see whether installation of a domestic device to decrease CaCO 3 levels around the time of birth can reduce this risk.

Atopic dermatitis: the skin barrier and beyond

“…Inherent properties of the water used for washing may also play an important role. A recent U.K. population‐based study reported that living in a hard‐water area was associated with up to 87% increased risk of AD at 3 months of age; the risk tended to be higher in children with FLG mutations . These findings were recently confirmed in a cohort study from Denmark, where early exposure to hard domestic water was associated with an increase in the relative prevalence of AD in the first 18 months of life .…”

“…The development of novel prevention strategies focused on the skin barrier is an area of active research. Emerging evidence on the impact of water hardness has raised the question of whether installing domestic water softeners around the time of birth for high‐risk children may prevent the condition from developing in infants. A U.K. interventional trial to test this is in progress (NCT03270566).…”

Effect of atopic skin stressors on natural moisturizing factors and cytokines in healthy adult epidermis

“…So‐called hard water appears to have the most negative effect on the skin barrier, which, in turn, may increase the risk of AD . Accordingly, a higher prevalence of AD in children residing in regions with hard domestic water has been found . A high calcium carbonate content is normally associated with an elevated pH, which may result in premature activation of serine proteases that, in turn, degrade corneodesmosomes .…”

Report from the first European Dermato-Epidemiology Network forum

“…The effect estimates remained similar after adjusting for filaggrin genotyping. However, a cross‐sectional analysis of the EAT study identified an increased risk of developing eczema by 3 months of age if the child lived in an area of hard water . Jabbar‐Lopez et al .…”