eczema-hard-water-bathing
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If you are asking whether eczema and hard water bathing are linked, the two sources checked for this guide do not show that bathing in hard water causes or worsens eczema, and they do not show that making bath water softer treats it. The one randomised trial tested a whole-home water softener in children, not bathing on its own, and it found no extra benefit over usual eczema care. The second source is a laboratory study of calcium in bath water. It did not measure eczema. The details below explain what each study measured and what it leaves open.
Quick answer
- The main trial enrolled 336 children aged 6 months to 16 years with moderate to severe eczema, all living in hard water areas of England. At 12 weeks, children whose homes had a water softener installed did not improve more than children given usual care.
- The trial changed the water for the whole home, not only the bath. The sources do not separate bathing from other water uses.
- The laboratory study showed that a baby cleanser can bind calcium in simulated hard bath water. Its only skin measurement came from three adults over 10 minutes.
- Neither source says that hard water bathing causes eczema, and neither gives a bathing routine that helps it. If you have eczema, follow the plan your doctor or dermatologist gave you.
What the trial studied
The trial was an observer-blind, randomised, parallel-group study that ran for 12 weeks, followed by a 4-week observation period. It was carried out in eight UK centres, with recruitment between May 2007 and June 2009. Children were eligible if they had a diagnosis of eczema under UK working party criteria and a minimum severity score of 10 on the Six Area Six Sign Atopic Dermatitis (SASSAD) scale. Children who had taken certain systemic treatments, or who already had a water treatment device at home, were excluded.
Participants were randomised to one of two groups. One group had an ion-exchange water softener installed plus usual eczema care. The other group had usual eczema care alone. Only one child per household was enrolled. The water softener used a resin to remove calcium and magnesium ions from household water. The trial used a generic unit, not a commercial brand, and the sources do not describe any other product.
The trial could not hide the treatment from families. A pilot study had found that the softened water produced more soap suds, so participants could tell which group they were in. For that reason the researchers used trained research nurses, who did not know the allocation, to score each child’s skin. The trial’s authors say this was the way to keep the main assessment free of observer bias.
What the trial measured
The primary outcome was the change in SASSAD score at 12 weeks, compared with the start of the trial. The trial also looked at sleep loss, itchiness, night scratching, the amount of topical corticosteroid or calcineurin inhibitor creams used, a questionnaire on the family impact of dermatitis, and a children’s quality of life measure. Night scratching and topical medicine use were blinded to treatment group. The sources do not report a measure of skin hydration, skin barrier function or the amount of calcium in the child’s skin.
Families were asked to bathe and wash clothes in the usual way. The sources do not say how often children bathed, how hot the water was, or whether they bathed or showered. Those details were not part of the trial’s analysis.
What the trial found
| Measure | Water softener plus usual care | Usual care alone |
|---|---|---|
| Children in the analysis (intention-to-treat) | 159 | 164 |
| Mean change in SASSAD at 12 weeks | −5.0 (20% improvement) | −5.7 (22% improvement) |
| Good or excellent improvement | 52% | 56% |
The difference between the groups at 12 weeks was 0.66 points in favour of the usual care group, with a 95% confidence interval of −1.37 to 2.69 and a p value of 0.53. An adjusted analysis gave a difference of 0.34 points (p = 0.74). The trial’s authors say that both groups improved during the trial, and that the confidence interval makes a clinically useful benefit from the softener unlikely to have been missed by chance. Twelve participants withdrew before the week 12 assessment, and one was excluded for incomplete baseline data.
The trial reported no clinically important difference between the groups on the blinded outcomes, which included night scratching and topical medicine use. Parents did report small benefits, and some secondary outcomes showed small statistically significant differences. The authors say those differences were likely caused by response bias, because parents knew which group they were in. Just over half of the families bought a softener at the end of the trial, mainly because they perceived an improvement in the eczema. The authors say it is unclear how much of that belief was based on prior expectation.
The trial also reported a subgroup point. Just under 30% of the children carried at least one filaggrin mutation, and those children did not show additional benefit compared with children without the mutation.
What the trial left out
- Bathing alone. The softener treated all water entering the home, except a drinking water tap at the kitchen sink where that was possible. The trial cannot separate the effect of bath water from the effect of water used for everything else.
- Showers or shower heads. The sources do not mention shower heads or spray types.
- Adults. The trial enrolled children and young people only.
- Long-term use. The main comparison ran for 12 weeks, with a 4-week observation period. The authors themselves note that the trial may have been too short to capture a treatment effect.
- Bath temperature, bath frequency, and cleansers. These were not part of the design or the analysis.
What the laboratory study measured
The second source is a 2016 paper in Clinical, Cosmetic and Investigational Dermatology. Its authors work for the company that made the cleanser tested, and the paper states that the studies were fully supported by that company. The paper is about how calcium behaves in bath water with a cleanser. It is not a study of eczema.
The in vitro part measured free calcium in simulated hard water between 100 and 500 ppm. At an in-use dilution of 1%, the cleanser reduced free calcium from about 500 ppm to under 200 ppm. At a 10% dilution it bound virtually all the free calcium. The anionic surfactant component of the cleanser contributed most of that effect.
The exploratory in vivo part was small. It involved three female participants aged 21 to 29 years, and it measured a reduction of about 15% in free calcium from simulated hard water over 10 minutes. The authors report that higher concentrations of free calcium in water were associated with higher rates of calcium absorption into the skin surface in adults. They write that bathing in hard water without a cleanser “might result in excess calcium absorption into the skin.” They also write that “The implications of this process for skin health is unclear, however, as the properties of adult and pediatric skin are different.”
The paper’s background cites observational studies linking hard water with atopic dermatitis, and it states that “Hard water is associated with atopic dermatitis (eczema).” The authors also say that the relationship between water hardness and eczema is not well characterised. Observational studies can show that two things occur together, but they cannot show that one causes the other.
Why the two sources do not answer the same question
The trial asks whether a whole-home softener changes eczema severity in children over 12 weeks. The laboratory study asks how a cleanser changes calcium in a test solution and, briefly, in three adults. Together they show two things: hard water contains more dissolved calcium, and some cleansers can bind that calcium in a test setting. Neither study shows whether that change matters for eczema in a real bath, and the trial never looked at bath water alone.
The background evidence the trial cites is also observational. In a Nottingham study of primary school children, the one-year prevalence of eczema was 17.3% in the hardest water category and 12.0% in the softest, with an odds ratio of 1.54 after adjustment for confounders. The trial describes this as an association, and so should a reader.
How we chose
This guide uses two sources only. Both are full-text articles hosted on the NIH PMC archive, and both were saved and read on 2026-10-28. The first is a randomised trial of a water treatment in children with eczema. The second is the only source found that measures calcium in bath water with a cleanser and includes a skin measurement. No other studies were opened for this draft, so the guide does not rank them against other research.
The two sources describe the trial’s assessment timing differently. The trial’s editor summary says the nurses assessed skin at baseline, 6, 12 and 16 weeks. The methods section says baseline, 4, 12 and 16 weeks. The guide reports the methods section and does not choose between the two descriptions.
What the sources do not say
- The sources do not test bathing in softened water against bathing in hard water as a separate exposure.
- The sources do not give a bathing routine, a bath length, or a water temperature for people with eczema.
- The laboratory study did not measure eczema, itch, skin barrier function, or any clinical outcome.
- The trial did not report the effect of its intervention on the skin of adults.
- The sources do not give a safety profile for cleansers used on eczema-prone skin.
- The sources do not say whether a cleanser that binds calcium changes the skin in people with eczema.
What we could not verify
- Whether the 15% reduction in calcium over 10 minutes, measured in three adults, applies to a child’s bath or to a real bath with a cleanser.
- Whether the trial’s results apply to people outside England, or to homes with different water chemistry.
- Whether the small secondary differences reported by parents reflect a real benefit. The authors say response bias is the likely cause.
- Why the trial’s two sources describe the assessment schedule differently.
If you have eczema
Follow the plan your doctor or dermatologist has given you. Do not stop or change a prescribed cream because of anything in this guide. If you are worried about your water, bring the question to your next appointment, and ask whether your water or your bathing routine is a factor for your skin. The sources do not give a routine, so the decision belongs to you and your clinician.
FAQ
Does hard water cause eczema?
The sources do not show that. The trial’s background cites observational studies that link higher water hardness with more eczema. An association is not proof of cause, and the sources do not settle the question.
Did a water softener help children with eczema in the trial?
No extra benefit was found over usual eczema care at 12 weeks. Both groups improved, and the difference between them was small and not statistically significant (p = 0.53).
Does a calcium-binding cleanser help eczema?
Neither source tested that. The laboratory study showed that a cleanser can bind calcium in a test solution, and it measured a small change in three adults over 10 minutes. It did not measure eczema.
Should I change how I bathe because of this?
The sources do not give a bathing routine. If you have eczema, ask your doctor or dermatologist what to do, and follow the plan they give you.
How long did the trial last, and how many children were in it?
The trial enrolled 336 children and ran for 12 weeks, followed by a 4-week observation period. The analysis included 159 children in the softener group and 164 in the usual care group.
Is this guide recommending a product?
No. This guide does not recommend a water softener, filter, shower head, cleanser or any other product.
Bottom line
The best trial on this question found that a whole-home water softener did not add to usual eczema care in 336 children over 12 weeks. The laboratory study showed that some cleansers bind calcium in hard bath water, but it did not measure eczema and it tested only three adults. Neither source shows that hard water bathing causes or treats eczema. If you have eczema, the first step is the plan from your doctor or dermatologist.
Sources
- Thomas KS, Dean T, O’Leary C, et al. “A Randomised Controlled Trial of Ion-Exchange Water Softeners for the Treatment of Eczema in Children.” PLoS Medicine. 2011;8(2):e1000395. https://pmc.ncbi.nlm.nih.gov/articles/PMC3039684/ (opened 2026-10-28)
- Walters RM, Anim-Danso E, Amato SM, et al. “Hard water softening effect of a baby cleanser.” Clinical, Cosmetic and Investigational Dermatology. 2016;9:339-345. https://pmc.ncbi.nlm.nih.gov/articles/PMC5072514/ (opened 2026-10-28)
