Prolonged breast-feeding is widely believed to protect infants against developing eczema and other allergic diseases. But a new study has found no evidence for the belief.

Researchers in Britain gathered data on more than 50,000 children ages 8 to 12 in 21 countries, assessing the prevalence and severity of eczema with skin examinations of the children, family medical histories and questionnaires about past symptoms. The children also received skin-prick tests for common allergens.

Even among children who had been breast-fed for six months or longer, there was no evidence that breast-feeding prevented eczema or limited its severity. The results were the same for children whose mothers had a history of allergy and for those who had a positive reaction to the allergens used in the skin-prick test.

In more affluent countries, breast-feeding actually was associated with a slight increase in the risk for eczema. The researchers suspect that this is because mothers who see an allergic reaction in an infant may try to breast-feed longer, not because breast-feeding causes the allergy.

"We're not questioning the benefits of breast-feeding," said Carsten Flohr, the lead author and a senior lecturer in pediatrics at Kings College London. "But when it comes to prevention of eczema, neither breast-feeding itself nor prolonged breast-feeding seems to be protective."

The study appears online in The British Journal of Dermatology.

Atopic dermatitis is a form of eczema that is caused by an inappropriate inflammatory response in the skin. Many children with atopic dermatitis also have food allergies, and skin contact with food allergens can make their atopic dermatitis worse.

It is unclear why this occurs, but it has been suggested that immune cells known as T cells that are sensitized by exposure to food allergens in the gut are responsible. Raif Geha and colleagues, at Harvard Medical School, Boston, have now generated data in a mouse model of food allergen-induced atopic dermatitis that support this idea. Specifically, their data indicate that skin contact with food allergens can lead to the reprogramming of gut-homing T cells into skin-homing T cells that mediate allergic skin inflammation. These data have important implications for the prevention and eczema cure treatment of atopic dermatitis in patients with food allergy.

New research finds that adults who suffered from eczema as children -- especially if they also had hay fever -- are nine times more likely to have allergic asthma when they're in their 40s.

The findings are based on about 1,400 adults who have been followed for five decades as part of Australia's Tasmanian Longitudinal Health Study. The study participants were assessed in 1968, when they were 7 years old, and then again in 2004 when they were about 44 years of age.

"In this study we see that childhood eczema, particularly when hay fever also occurs, is a very strong predictor of who will suffer from allergic asthma in adult life," lead study author Pamela Martin, a University of Melbourne graduate student at the Murdoch Childrens Research Institute, said in a university news release. "The implications of this study are that prevention and rigorous treatment of childhood eczema cure and hay fever may prevent the persistence and development of asthma."

Allergic asthma is airway obstruction and inflammation that's triggered by inhaled allergens such as dust mites, pet dander, pollen and mold.

According to Martin, the study is the first to examine childhood eczema and hay fever and their connection to allergic versus nonallergic asthma. The linkage between childhood illnesses and adult asthma is called the "atopic march."

"If successful strategies to stop the 'atopic march' are identified, this could ultimately save lives and health care costs related to asthma management and treatment," Shyamali Dharmage, principal investigator of the Tasmanian Longitudinal Health Study and associate professor at the University of Melbourne's School of Population Health, said in the news release.

The researchers suspect that about 30 percent of cases of allergic asthma could be the result of childhood eczema and hay fever.

Infants with eczema are at high risk of having peanut and other food allergies, British researchers report.

"We were shocked to find out that even in the first year of life, over 20% of infants with eczema already were sensitized [showed susceptibility] to peanut allergy," says Graham Roberts, MD, a pediatric allergist at King's College London.

Roberts tells WebMD that by the time they enter school, children with eczema have a high rate of peanut allergies.

"But we didn't know how early the peanut allergy started; we thought may at 3, 4, or 5 years of age," he says.

The new research suggests peanut allergy develop much earlier, Roberts says.

The study involved 640 infants aged 4-11 months with eczema.

The researchers measured blood levels of immunoglobulin E (IgE), an immune system protein the body makes in response to allergens.  A positive result means a person is sensitive to and likely to be allergic to a certain food.

The results showed:

• 23% of the infants were sensitive to peanuts.
• 31% were sensitive to cow's milk.
• 22% were sensitive to sesame.
• 16% were sensitive to Brazil nuts.
• 20% were sensitive to hazel nuts.
• 21% were sensitive to cashews.
• 14% were sensitive to almonds.

Sixteen percent of the infants tested positive for more than four foods.

The findings were presented here at the annual meeting of the American Academy of Eczema Allergy, Asthma & Immunology.