Children are being prescribed a special type of water softener to reduce symptoms of eczema, the skin condition that affects up to one in five school-age youngsters.
The move follows research which has shown that eczema is up to 50per cent more common among primary school pupils who live in hard water areas.
Eczema can run in families, but environmental factors are also suspected of playing an important role in causing the disorder.
However, apart from allergies to house dust mites and possibly some foods, little is known about other environmental triggers that may increase the risk.
Atopic eczema is the most common form of the condition, and can affect both children and adults.
Symptoms include itchiness, skin dryness, redness and inflammation, as well as sleep loss and distress.
There is no cure, and treatments, including lotions of various kinds as well as steroid creams, are aimed merely at easing symptoms.
Researchers at Nottingham University, who carried out the research on 7,000 children, found that eczema was 54 per cent more prevalent in areas with the hardest water supplies.
They are now starting a clinical trial using water softeners.
The new trial involves 310 children aged between six months and 16 years.
The children will have ion-exchange water-softening equipment installed in their homes for between four and 12 weeks.
The units will reduce the water hardness to around zero.
To soften hard water, the minerals which cause hardness — usually calcium and magnesium — are removed.
There will therefore be a separate drinking water supply installed for the duration of the trial.
Hard water when drunk has a number of health advantages, and has been linked to lowered risk of heart disease.
Exactly how the water-softening device could alleviate eczema is not clear, but one theory is that the salts in hard water cause dryness which leads to irritation.
Another theory is that the salts theselves irritate the skin.
A third suggestion is that using hard water means larger quantities of soap and shampoo need to be used because they do not work as well in hard water, and that overuse can irritate the skin of eczema sufferers.