Being exposed to cat allergens early in life may spark eczema - if you carry a key gene fault, a study has suggested.

Scientists found having the mutant FLG gene increased the risk of eczema in a baby's first year twofold, but adding exposure to a cat quadrupled that risk.

The study, of 892 babies born in the UK and Denmark, was published in the Public Library of Science journal.

However, a UK expert said other research suggested cats may actually reduce the risk of eczema.

The study, led by a team at the University of Dundee, found exposure to dogs made no difference.

Our data suggest that cat but not dog ownership substantially increases the risk of eczema in the first year of life in children with FLG 'loss of function' variants Study researchers

Rates of eczema, which can cause dry, itchy skin, have been rising in the UK in recent years.

The cause of the condition is not fully understood, but it is known that chemicals which cause allergic reactions do seem to trigger flare-ups.

Scientists believe an interplay between these chemicals and our genes may be key to the initial development of the condition.

The Dundee team has been investigating the potential role played by the FLG gene, which it believes is crucial in maintaining the skin's role as a protective barrier.

Some variants of the gene stop it working properly, but faulty genes alone do not explain eczema - as some people appear to carry them and never suffer from the condition.

Environmental factors

The Dundee study looked for a connection between "environmental" factors and the triggering of the disease in children.

Working with the universities of Manchester and Copenhagen, the team looked at groups of babies to see what difference exposure to cat, dog and dust mite allergens made to those carrying the variants of the FLG gene.

Researchers found that, on average, the variants on their own roughly doubled the chances of eczema in the first 12 months of life.

In those families who also owned cats at the time of the birth, the risk was almost quadrupled.

There was no significant increase in the risk if there was dog or dust-mite exposure.

The researchers wrote: "Our data suggest that cat but not dog ownership substantially increases the risk of eczema in the first year of life in children with FLG 'loss of function' variants".

However, Dr Michael Cork, a dermatology expert from the University of Sheffield, said the study was relatively small, and the results should be interpreted cautiously.

He said: "There is plenty of other evidence that exposure to cats can actually protect against the development of eczema.

"It is possible that it could actually induce tolerance in children.

"This is a highly complex area, and any results like this need to be weighed alongside other studies."

Almost a quarter of seven to nine-year-olds in West Cumbria suffer to some degree from the skin disorder eczema, researchers claim.

Scientists from Newcastle University tested 800 pupils from 41 schools across the area, finding evidence of the condition in 24% of cases.

The gene Filaggrin, which has been linked to eczema, was thought to be responsible for 4% of these.

Irritants like chemicals and detergents are also thought to be a factor.

The researchers also studied samples of umbilical cord blood donated by mothers at Whitehaven's West Cumberland Hospital between 1996 and 2003.

Dermatologist Dr Sara Brown said: "We were surprised by the fact that nearly one in four children has eczema.

"The number of people we're seeing with eczema has increased over the past 10 to 20 years, possibly caused by environmental factors, although we know that our genetic make-up is also important.

"If one of the genes they inherit is faulty then they will have a 25% risk of getting eczema. If the child inherits genes from both parents that contain the fault then they will have a 90% risk of having eczema."

The study will help scientists find better treatment for the condition, she added.

Eczema study reveals skin's broken defences

The skin of people with eczema fails to produce effective amounts of two key bacteria-killing molecules, a US team has discovered.

The results of this "seminal study" could account for why about one third of people with atopic dermatitis - the most common form of the disorder - develop severe skin infections. It may also force a rethink of precisely what eczema is and lead to new treatments for millions of sufferers.

"This study helps explain why 90 per cent of atopic dermatitis patients are colonised by Staphylococcus aureus and 30 per cent develop active infections," says lead author Donald Leung at the National Jewish Medical and Research Center in Denver.

Skin with an intact immune system produces high levels of two peptides called LL-37 and HBD-2 as part of the inflammatory response to infection. These peptides fight viruses and fungi, as well as bacteria.

Eczema and psoriasis both trigger an inflammatory response even in the absence of an infection, but Leung's team found that while psoriasis patients produce normal levels of the two peptides, people with eczema do not.

They showed that the peptides are not produced when the skin's outer barrier is breached in eczema sufferers, because an over-production of two inflammatory cytokines inhibits the normal expression of genes for the peptides.

Defences down

"This seminal study shows that in certain human diseases, the antimicrobial defenses of the epithelium are suppressed because of a dysfunctional inflammatory process," writes Michael Zasloff of Georgetown University Medical Center, in an editorial accompanying the paper in the New England Journal of Medicine.

The findings open up a host of questions, says Zasloff, including to what extent the symptoms of eczema are due to an allergic trigger, such as a foodstuff - and to what extent the itchy, inflamed skin is a response to a build-up of bacteria on the skin, caused by under-production of the peptides.

Atopic dermatitis is inherited, and usually lessens or vanishes in adulthood. Leung's team studied eight patients with moderate to severe atopic dermatitis, 11 with psoriasis and six healthy people. They hope the findings could lead to effective new treatments for millions of sufferers. Currently, antibiotic and steroid creams are commonly prescribed.

But a peptide-based cream "might be more potent and would act on the skin to help healing, so the damage in atopic dermatitis would repair more quickly," says co-investigator Richard Gallo, associate professor of medicine at the University of California, San Diego. In 1994, Gallo was the first to discover anti-microbial peptides in mammalian skin.

Key proteins low in eczema sufferers

THE skin of people with eczema fails to produce enough of two key molecules that kill bacteria. That could explain why so many people with the disorder develop severe skin infections. It may also force a rethink of precisely what eczema is.

Normal skin produces a variety of chemicals to fight off bacteria and fungi, including two proteins called LL-37 and HBD-2. Donald Leung's team at the National Jewish Medical and Research Center in Denver, Colorado, has found that people with the common form of eczema, atopic dermatitis, produce only a tenth as much LL-37 and HBD-2 as people with no skin problems or with psoriasis.

Both eczema and psoriasis are characterised by skin inflammation, even though there is no obvious infection. In eczema, some of the inflammatory chemicals switch off the production of LL-37 and HBD-2, Leung's team reports in The New England Journal of Medicine (vol 347, p 1151).

The finding opens up a host of questions about eczema, says Michael Zasloff of Georgetown University Medical Center in Washington DC, such as to what extent eczema is due to an allergic trigger, such as a food - and to what extent the itchy, inflamed skin is a response to a build-up of bacteria, caused by the underproduction of the proteins. It also open up the possibility of treating skin infections in eczema with creams containing either the proteins, or compounds that boost their production.