Australian researchers are closer to cracking an investigation into the exponential increase in childhood food allergies after confirming a genetic link between allergies and eczema.
The latest research shows infants with a genetic predisposition to eczema may be at risk of developing food allergies, but actually consuming food could protect against developing a full-blown allergy.
The study by Murdoch Childrens Research Institute scientists in Melbourne backs up their previous finding that introducing cooked egg to babies at four to six months reduced the risk of developing an egg allergy.
The new findings, published in the Journal of Allergy and Clinical Immunology, suggested both genetic and environmental factors played a role in the development of childhood food allergies, study leader Professor Katie Allen said.
DNA samples were taken from 700 infants to investigate changes in a gene linked to eczema, called filaggrin, and the risk of developing food allergy in one-year-olds.
The study found babies with changes in the filaggrin gene were more likely to have a positive skin prick test to food allergens, but did not necessarily go on to develop a food allergy.
Prof Allen said the finding suggested babies were sensitive to food through the skin, but could counteract that by developing immune tolerance in the gut.
Using the earlier example of the egg allergy findings, Prof Allen said the filaggrin gene would increase the risk of a positive skin prick test, but if egg was consumed then that would decrease the risk of a full-blown allergy.
"But ... if you have the filaggrin gene and avoid the egg, then you are more likely to get food allergy," Prof Allen said.
The function of the filaggrin protein is to prevent water loss from the skin and protect the body from outside allergens.
Therefore, when this process breaks down it can lead to sensitisation including to foods through the skin.
Prof Allen said the research supported this theory, which could have implications for improving the skin care of babies by increasing hydration and reducing the use of soaps which can dry out the skin.
"Our research supports the biological model that we want to try and keep the skin in the best condition possible before the baby starts to eat," Prof Allen said.
"This is genetic evidence that a broken-down skin barrier increases the risk of having a positive skin prick test in that critical period before the baby has started to eat."
The research forms part of a wider study led by Prof Allen to track food allergy prevalence and causes.