There is no clear evidence that probiotics, the "friendly" bacteria strain of lactobacillus, prevent eczema -- a frequent precursor to asthma, a study has said.

Published in the journal Pediatrics on Monday, the study fuels the debate over whether probiotics, sold as dietary supplements, have protective effects against colds, tummy bugs and more serious conditions, Xinhua news agency reported.Author Michael Cabana, director of the division of general pediatrics at the University of California, Benioff Children's Hospital, worked with his colleagues to see if the probiotic would work among infants who were at high risk of developing asthma, due to one or both parents having the condition, which is caused by both hereditary and environmental factors.

Exactly half of the 184 newborns received capsules of the probiotic for the first six months of life, while the second group of 92 newborns received placebo capsules with the same look and feel as the probiotic.The results showed little difference: At age two, 30.9 per cent of the placebo recipients were diagnosed with eczema, versus 28.7 per cent of the probiotic group.Found in yogurt, kefir and fermented foods, and described by the World Health Organization (WHO) as "live micro-organisms which when administered in adequate amounts confer a health benefit on the host", probiotics are believed to enhance the defensive action of the cells that line the gut by stimulating healthy immune function and inhibiting the growth of viral and bacterial pathogens.

Regarding the new study, Cabana said the absence of infectious exposure at a critical point in immune system development leads to a greater risk for eczema and asthma.Additionally, lack of key bacteria in the infant intestinal microbiota has been associated with the later increased risk of allergic disease.Therefore, supplementing with specific probiotic strains may modify the entire microbiota community patterns and decrease this risk.However, in an editorial titled "Probiotics in the Child Care Center: Context Matters" and published in the same issue of Pediatrics, Cabana and Daniel Merenstein of Georgetown University Medical Centre in Washington, suggest that as breast milk contains natural compounds that act like prebiotics, the best source of influencing a child's gastrointestinal tract is breast milk.