Eczema, or atopic dermatitis, is a chronic inflammatory skin condition characterized by a compromised skin barrier, leading to dryness, itching, and inflammation. Water quality is investigated as a potential environmental factor influencing severity. Hard water contains high concentrations of dissolved minerals, primarily calcium and magnesium ions, while soft water has these minerals removed or significantly reduced. This article examines the scientific relationship between water hardness and eczema severity, focusing on the evidence surrounding the use of soft water.
Understanding Hard Water and Skin Health
The presence of calcium and magnesium ions in hard water can directly interfere with the skin’s natural protective function. Healthy skin maintains a slightly acidic pH, often referred to as the acid mantle, but the alkalinity of hard water can raise this pH balance. A shift toward a more alkaline environment disrupts the skin barrier, increasing the potential for transepidermal water loss (TEWL). This leaves the skin more susceptible to irritation and colonization by certain bacteria.
The minerals in hard water also react chemically with soaps and synthetic detergents. This reaction forms an insoluble precipitate, often seen as soap scum, which can leave a sticky residue on the skin after bathing. This residual film can irritate the already compromised skin barrier. It may also further exacerbate dryness and itching by interfering with the skin’s natural moisturizing factors and leaving behind abrasive mineral deposits.
Research on Water Softening and Eczema Severity
While the mechanistic evidence strongly suggests that hard water is theoretically damaging to eczematous skin, clinical trials investigating the benefit of water softening systems have yielded mixed results. The Softened Water Eczema Trial (SWET) examined the effect of ion-exchange water softeners on children with eczema. The primary outcome, measured by an objective eczema severity score (SASSAD), showed no significant difference in improvement between the group using a water softener and the control group receiving usual care.
Both groups showed a similar degree of improvement over the 12-week trial period. The mean reduction in the severity score was nearly identical, indicating that the water softener provided no additional measurable benefit over standard eczema treatments. However, some secondary outcomes based on parental reports, including itch and quality of life measures, did show small, statistically significant improvements in the water softener group. Experts suggest these subjective improvements might be due to a response bias, as the objective clinical data did not confirm a large-scale reduction in disease severity.
Methods for Treating Hard Water
For individuals who choose to mitigate the potential effects of hard water on their skin, several household solutions exist. The most effective method for reducing water hardness throughout the entire home involves installing a whole-house ion-exchange water softener. These systems work by replacing the calcium and magnesium ions with sodium ions. They are generally installed at the main water entry point and require regular maintenance.
Alternatively, point-of-use devices, such as showerhead filters, are available as a less expensive and less invasive option. However, most simple filtration systems, including carbon filters, are primarily designed to remove chlorine and other contaminants. They are much less effective at removing the minerals that cause water hardness, making the whole-house ion-exchange system the primary method for achieving soft water for bathing.
Temperature and Chemical Considerations in Bathing
Water hardness is just one of several factors in bathing practices that can influence eczema symptoms. Water temperature plays a role, as hot water strips the skin of its natural oils. This loss can lead to increased dryness, itching, and inflammation. Individuals with eczema should use lukewarm water for bathing to preserve the skin’s moisture barrier.
Chemicals used to disinfect the public water supply, such as chlorine, can also be a source of irritation for sensitive skin. Chlorine can sometimes strip the skin’s surface, leading to dryness and irritation. Baths or showers should be kept brief, and a thick emollient or moisturizer should be applied immediately after drying the skin to seal in moisture.