Some people with an itchy allergic skin condition seem to be more vulnerable to infections, perhaps because they lack natural antibacterial chemicals in their skin, scientists say.

Researchers reported Thursday that people with eczema often make too little germ killer, which may make them prone to staph infections of the skin.

For years, scientists have viewed skin as simply a protective barrier from the environment. Now researchers are learning how skin may produce its own chemical defences.

Scientists knew the antimicrobial chemicals, called peptides, protected animals from infection. Now they have shown how significant the chemicals are in people.

The research team said the discovery suggests replacing the peptides or stimulating their production could help fight off staph infections in people with eczema.

But one of the researchers, Dr. Tomas Ganz of UCLA's medical school, cautioned more research is needed to show how these chemicals contribute to eczema patients' infections.

Itchy eczema often causes people to scratch their skin, which leaves the protective barrier inflamed.

The condition affects about 15 million people in the U.S., and about 90 per cent of them have long-term staph infections on their skin that don't always cause symptoms.

New approach to body's defences?

Scientists compared people with eczema and people with psoriasis, a disease with similar symptoms such as dry, itchy skin.

They looked at two antimicrobial peptides, known as beta-defensins and cathelicidins. Both are commonly found in inflamed skin. But doctors noticed people who have psoriasis rarely suffer skin infections.

To evaluate levels of the two peptides, researchers looked at eight eczema patients, 11 psoriasis patients, and six healthy people. They found the eczema patients had no or nearly none of the two peptides.

People with psoriasis had significant levels of both peptides.

Dr. Enno Christianson, a scientist at the University of Kiel in Germany, said the study suggests a new way of looking at the body's defences that does not involve the immune system. Christianson has discovered a number of human defensins.

But Dr. Jon Hanifin of Oregon Health Sciences University and the National Eczema Association's scientific advisory committee, said the team hasn't shown the cause and effect relationship behind the peptides. He suggested the researchers may have overstated their conclusions.

The study appears in Thursday's issue of the New England Journal of Medicine.

Veterans Affairs, the National Institutes of Health, the University of Colorado Cancer Center, the Academy of Allergy, Asthma and Immunology and the Stern Foundation helped fund the research.