Softened Water Eczema Trial

Could water softeners help to relieve the symptoms of eczema in children with moderate to severe eczema?

What was this study about?

Families of eczema sufferers and some doctors have said that living in a hard water area may make eczema worse. Recently, researchers found that eczema is more common in primary school children living in hard water areas in the UK compared with children living in soft water areas. No one really knows why, but it could be because hard water contains high levels of calcium and magnesium, leading to increased use of soaps which can act as skin irritants.

The aim of this research study was to see if eczema can be improved by deliberately softening all the water used in the home (except at one tap in the kitchen which supplied mains water for drinking). It involved children with moderate or severe eczema.

The SWET study was a cross-over trial. All of the homes where the children lived had a water softener installed for either 12 weeks (for the main comparison) or four weeks, depending on the group they are in. During the study, doctors (who were not told whether the child had a water softener installed or not) assessed the child’s eczema at regular hospital clinic visits.

What difference did this study make?


The primary outcome, change in eczema severity (Six Area Six Sign Atopic Dermatitis Score, SASSAD) at 12 weeks, was measured by research nurses who were blinded to treatment allocation. This showed no benefit over usual care for those allocated to receive a water softener.

Participants reported evidence of benefit but it is likely that such improvements were the result of response bias, since they were aware of their treatment allocation.

It was concluded that based on the results of this study water softeners cannot be recommended for the treatment of eczema in children. Whether or not individuals consider there are sufficient benefits to justify the purchase of a water softener is something for them to decide.

Type of study

Randomised trial

Contact details


Who funded the study?

This trial was funded by the National Institute for Health Research Health Technology Assessment Programme – part of the NHS.

When did it take place?

The trial began enrolling children in May 2007 and the last child was enrolled in June 2009.

Where did it take place?

In hard water areas in Nottingham, Leicester, Lincoln, North London, Cambridge, Portsmouth and the Isle of Wight.

Who was included?

336 children between the ages of 6 months and 16 years who had moderate to severe eczema.