Scientists in Nottingham studied more than 4,000 local primary school children and found a higher prevalence of atopic eczema in the areas where there was hard water in the domestic supply.

The researchers say it is possible that the high levels of calcium and magnesium in the hard water are irritating the skin of the children. Their eczema might also be a reaction against the excess soap and shampoo that is used to generate a lather when washing or bathing in hard water.

"We know, for example, that the skin of children with eczema or a tendency to eczema, tends to be drier, rendering it more liable to irritation," said Dr Hywel Williams from the Queen's Medical Centre at the city's University Hospital, one of the authors of the study.

Further work

However, he warned against a sudden rush to buy water softeners. He said the work did not necessarily mean soft water was good for eczema.

Dr Hywel Williams: We need to test water softeners

"I think it's essential to do a randomised controlled trial on eczema sufferers to see if a proper water softening device versus a placebo device really makes any difference."

The study involved giving questionnaires on eczema to the parents of 4,141 primary school children and to 3,499 secondary school children in south Nottinghamshire.

Just over 17% of the primary school children living in areas with the hardest water had had eczema for one year, and 25.4% had lifetime eczema, whereas 12% of primary school children living in areas with soft water had had eczema for one year, and 21.2% had lifetime eczema.

The same link between eczema and hard water was not evident for children of secondary school age.

Dr Williams said the differences between primary and secondary pupils might be explained by the differences in the way they came into contact with water.

"Perhaps the skin changes," he said. "Certainly, the skin becomes greasier in adolescence. There could be subtle changes in the skin which renders it less susceptible to irritation."

Common type

Eczema is a non-infectious, non-contagious skin condition, marked by dryness, rashes, itching, and in some cases the formation of blisters.

Atopic eczema is the most common type of eczema.

Atopy is a term which is used to describe people that are born with very sensitive mucous membranes and skin. These people are likely to develop other atopic disorders such as asthma and hay fever.

Nearly three-quarters of the people with this type of eczema have a family history of atopic disorders. More than two-thirds of atopic eczema cases improve by the age of four.

However, for some individuals the problem can last their whole life.

The Nottingham research was led by Nick McNally and drew on the expertise of a number of university and medical facilities.