Study links hard water to eczema
New research examines the possible link between hard water in the home and atopic dermatitis in infancy.
Domestic water hardness and chlorine have been suggested as important risk factors for atopic dermatitis (AD). One recent study by researchers from Kings College London, United Kingdom, explored the potential associations between domestic water calcium carbonate (CaCO3) and chlorine concentrations in home water systems, damage to the skin's natural barrier, and incidences of AD in infancy.1
Previous studies conducted in the UK, Japan, and Spain have suggested links between domestic water hardness and the risk of eczema in schoolchildren, but such association has not previously been studied in early infancy, claims the institution.
For this study, researchers recruited 1300 3-month-old infants from families across the UK, gathering information about levels of calcium carbonate and chlorine in their respective household water from local suppliers. The subjects were already participating in a study examining how to prevent food allergies in young children.
Researchers checked the infants for AD and assessed subjects’ skin barrier function by measuring transepidermal water loss (TEWL) on the skin of an unaffected forearm. They also screened for mutations in the filaggrin (FLG) gene, which codes for a key skin barrier protein. According to the National Institutes of Health's US National Library of Medicine, filaggrin plays a critical role in the skin's barrier function, bringing together structural proteins in the outermost skin cells to form tight bundles, and flattening and strengthening the cells to create a strong barrier. In addition, "processing of filaggrin proteins leads to production of molecules that are part of the skin's 'natural moisturizing factor,' which helps maintain hydration of the skin. These molecules also maintain the correct acid level (pH) of the skin, which is another important aspect of the barrier."
The UK study determined that living in an area with hard water was associated with up to an 87% increased risk of eczema at age 3 months, independent of the domestic water’s chlorine content. The risk tended to be higher in children with mutations in the FLG skin barrier gene, however the difference did not reach statistical significance.
Possible study limitations included the lack of information about the study subjects' exposure to swimming pools. Such exposure to water containing a considerably higher level of chlorine than domestic water could have had an added injurious impact on skin barrier function and risk of eczema.