Is soft water better for your skin?

Researchers in the United Kingdom ran the Softened Water Eczema Trial (SWET), published in PLOS Medicine in 2011. It was an "observer-blind randomised trial involving 336 children (aged 6 months to 16 years) with moderate/severe atopic eczema." All of them lived in hard-water areas, defined as "≥200 mg/l calcium carbonate." Half had an ion-exchange softener installed plus their usual eczema care. The other half had usual care alone.

The nurses who scored the children's eczema did not know which group each child was in. After 12 weeks, "the mean change in SASSAD at 12 weeks was −5.0 (20% improvement) for the water softener group and −5.7 (22% improvement) for the usual care group." SASSAD is the eczema severity score. The difference between the groups was small and not statistically significant (p = 0.53). The authors concluded that "water softeners provided no additional benefit to usual care in this study population."

A few points keep that result in proportion:

• Both groups improved. "Eczema severity improved for both groups during the trial," so the softener did not make a measurable difference on top of normal care.
• Some parents reported small gains. The authors say small differences in some outcomes reported by parents were probably response bias. In their words, "it is likely that such improvements were the result of response bias, since participants were aware of their treatment allocation." Families knew whether they had a softener.
• A few parents saw the opposite. "The parents of two participants believed their child's eczema had worsened as a direct result of installation of the water softener," and one more family had the same worry. Those are reports, not measurements.
• Industry helped. A consortium of water treatment companies gave technical help and softener units. The trial itself was funded by the UK's National Institute for Health Research.

The trial studied children who already had eczema. It says nothing about adults, or about whether soft water helps normal skin.

The authors are clear about the limits of their result. It applies "only to children with moderate to severe eczema," and they say "it is possible that water softening is beneficial for milder forms of eczema, or in adults with other eczema types." The trial also "did not address the issue of prevention of new cases of eczema," so it cannot say whether hard water plays a part in eczema starting in the first place. It lasted 12 weeks. The authors reasoned that any effect would have appeared sooner than that, and "there was no hint that the intervention group was starting to show more improvement than the control group towards the end." They also note that families kept using soap during the trial, and that "evidence of how much soap was actually used was not collected." So the trial cannot say whether using less soap with a softener would change the result.

The paper also records what families did afterward. "Just over 50% chose to buy the water softener at the end of the trial," and the reasons included "perceived improvements in the eczema" and "wider benefits of the softeners." The authors leave that call to the household: "Whether or not the wider benefits of installing a water softener in the home are sufficient to justify the purchase of a softener is something for individual householders to consider on a case-by-case basis." That is a fair way to put it. The trial does not show that a softener treats eczema. It also does not show the purchase is a mistake if you want it for other reasons.

The trial paper's discussion explains why the idea is plausible. It notes that "hard water results in more soap and detergent use, which can directly irritate the dry skin found in people with eczema," and that "soap also reacts with calcium in hard water to form small chalk particles which can irritate eczematous skin." So hard water may matter for eczema. The trial tested whether removing the hardness fixes it, and in that study it did not.

There is a simpler reason for the difference in feel. Penn State Extension says "hard water leaves scales on pots, soap films on skin, and detergent curds in the washing machine." When the hardness is gone, that film is gone too. The trial's pilot study found that softened water "produced more soap suds," so soap lathers more and rinses differently. Some people may read that as softer skin, and others may feel a slick residue. Neither impression is a measurement of skin health.

A softener swaps calcium and magnesium for sodium. Penn State says the exchange "adds 7.5 milligrams per quart for each gpg of hardness removed," and Nebraska Extension gives a rate of about 8 mg/L per grain per gallon. The Phoenix water quality report lists hardness of 172 to 302 ppm, or 10 to 17.6 grains per gallon, so a softener adds roughly 80 to 140 mg/L of sodium to that water. The sodium matters for drinking water for people on a sodium limit, not for the skin, and it is one more reason to ask a doctor about the whole picture. Our page on whether you can use potassium instead of salt covers that side.

Start with a clinician, then decide about the plumbing on its own merits.

1. 1See a doctor or dermatologist first. Dry or itchy skin has many causes, and the trial's finding was for eczema care, where treatments come from a clinician.
2. 2Buy a softener for the plumbing, not the skin. Its benefits are scale on fixtures and water heaters, and less soap and detergent film. Our page on the benefits of a whole-house softener separates what has evidence from what does not.
3. 3Check what is really in your water. A hardness test strip or an independent lab test tells you what your tap reads. Our page on how hard Phoenix water is has the city's range.
4. 4Ask about your own case. The trial studied one group of children under one set of conditions. A doctor can tell you whether anything in the findings applies to you or your family.
5. 5If you are comparing systems, read water softener versus reverse osmosis. RO treats drinking and cooking water, not showers.

HQ Plumbing & Air is licensed and insured. We can test your water hardness and explain what a softener would and would not change. We offer free estimates and upfront pricing.

If you are considering a shower head product instead, see whether a shower head water softener helps hair and skin.