The incidence of eczema is increasing dramatically in England, data suggests.
There was a 42% rise in diagnosis of the condition between 2001 and 2005, by which time it was estimated to affect 5.7m adults and children.
One potential explanation for the rise is increased frequency of bathing and use of soap and detergents.
A paper in the Journal of the Royal Society of Medicine says eczema is thought to be a trigger for other allergic conditions.
GP records of over 9m patients were used by researchers to assess how many people have the inflammatory skin disorder.
It showed that by 2005, one in nine of the population had, at some point, been affected by eczema.
The highest rate was in boys aged between five and nine.
Prescriptions increased by 57% over the five-year study period and in 2005, GPs issued 13.7m scripts.
Study leader Professor Aziz Sheikh, chair of the allergy and respiratory research group at the University of Edinburgh, said he expected to see a rise but it was fairly marked given the short time period.
"What's quite striking is the very high proportion of people who are getting eczema, it's an incredibly common disorder.
"Why eczema is important is increasingly we think eczema is a herald condition for individuals to go on to develop other allergic conditions, such as asthma and allergic rhinitis."
The theory is that allergens may be able to cross the skin in people with eczema to cause disease whereas in people without the condition the skin is able to act as a barrier.
He added that it is likely that a proportion of individuals have a genetic predisposition to develop eczema but that environmental factors also play a large part, and it is these which are likely to be causing the increase.
"The environmental factors are frequency of bathing and use of soaps and detergents."
It is also likely that some of the rise is due to better awareness and diagnosis.
He added that more research was needed on whether diagnosing and managing eczema properly early in life could prevent people going on to develop other conditions.
"The basic science suggests we can but the trials need to be done."
Margaret Cox, chief executive of the National Eczema Society, said the general theory was eczema had been increasing but it was thought the rise had levelled off.
"We do know there has been a huge rise in allergic disease of all sorts and what I would like to think is we're seeing some small signs of people concentrating their minds on eczema."
She agreed that modern living seemed to be having an effect.
"Water use dries up the skin and soaps and detergents degrease the skin.
"We are using quite a lot of these products from an early age."