Hard water, hair, skin and eczema: what the evidence says

The short answer

The evidence is mixed and still developing:

• Children living in harder water areas are more likely to have eczema in observational studies, but the certainty of that evidence is very low.
• In a randomised trial of children with eczema, installing a water softener did not improve eczema severity as assessed by nurses who did not know which homes had one.
• Whether softening water can prevent eczema in babies is still being studied.
• A small laboratory study found hard water did not weaken hair strands.

Eczema: the SWET trial

The Softened Water Eczema Trial (Thomas and colleagues, PLoS Medicine, 2011) randomised 336 children aged six months to 16 years with moderate or severe eczema living in hard water areas. After 12 weeks, eczema severity improved by a similar amount with or without an ion-exchange softener. Parents in the softener group reported small improvements, but they knew they had a softener, and the researchers thought this was likely to reflect bias. The authors concluded that softeners gave no additional benefit to usual care and said they could not recommend them for treating moderate or severe eczema in children.

Eczema: what the wider research shows

A 2021 systematic review (Jabbar-Lopez and colleagues, Clinical and Experimental Allergy) pooled seven observational studies with 385,901 participants and found higher odds of eczema in children exposed to harder water (an odds ratio of 1.28, meaning roughly a quarter higher odds), but rated the certainty of this evidence very low. Two randomised trials showed no difference in objectively measured severity in established eczema. Two studies of how skin reacts found more of the detergent sodium lauryl sulphate (used in many soaps and shampoos) stayed on the skin after washing in harder water. A 2016 UK study of 1,303 three-month-old infants (Perkin and colleagues) found an association between high water hardness and visible eczema, but it could not show cause and effect, and the authors called for an intervention trial.

Can softened water prevent eczema in babies?

This is not yet known. The SOFTER pilot trial (Jabbar-Lopez and colleagues, 2022) randomised 80 families in hard water areas (above 250 mg/l as calcium carbonate) in and around London to test whether a full trial would be practical. Fewer babies in softened-water homes had visible eczema at six months (33% compared with 48%), but the pilot was not designed to test effectiveness, no statistical testing was performed, and the range of plausible results included no difference at all, so the result could be down to chance. Separately, DWI advises that artificially softened water should not be used to make up baby feeds.

Hair

Evidence here is limited. A small laboratory study (Srinivasan and colleagues, International Journal of Trichology, 2013) soaked shed hair from 15 volunteers in hard water (212.5 ppm as calcium carbonate) or distilled water on alternate days for 30 days and found no significant difference in tensile strength or elasticity. It did not test how hair looks or feels after washing with shampoo. Hard water does make soap and shampoo lather less, which can affect how hair feels.

Looking after dry or eczema-prone skin

The NHS advises using emollients regularly, washing with an emollient instead of soap, and avoiding personal triggers such as certain soaps and detergents. The National Eczema Society notes that household cleaners and detergents can irritate the skin and suggests gloves and emollient after wet work. Speak to a pharmacist about mild eczema and a GP if it is severe or treatment is not working. Get urgent advice from a GP or NHS 111 if eczema looks infected or suddenly gets worse.

If you are considering a softener

A softener can reduce limescale, but the SWET trial does not support buying one to treat eczema. If you install one for other reasons, keep an unsoftened drinking-water tap and do not use softened water for baby feeds, as DWI advises. Check your area’s hardness first.

Check your area’s published hardness · Hard water areas in the UK · Convert hardness units (mg/l, °Clark, °dH) · How to soften hard water · Shower filters for hard water

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