Special baby formula sold in UK supermarkets does not reduce the risk of eczema and allergies, according to a new study.
Research funded by the Food Standards Agency (FSA) found that hydrolysed formula - a type of formula treated with heat to break down the milk proteins - offers no benefit to babies at risk of developing allergies.
In the UK, there is no official guidance recommending the formulas but the European Academy of Allergy and Clinical Immunology (EAACI) - whose advice is noted by British clinicians - says infants at high risk of developing an allergy "can be recommended a hypoallergenic formula" for the first four months of life.
A review of the evidence published by the Cochrane Library also suggests that hydrolysed formula reduced the risk of allergy, including milk allergy.
But new research led by Imperial College London found no such protective effect.
The study, published in the British Medical Journal (BMJ), reviewed data from 37 different trials into hydrolysed baby formula.
It found there was no significant reduction in the risk of developing eczema, wheezing, or food allergy (including cow's milk allergy). Some of the trials also investigated risk of developing type 1 diabetes, but no link was found.
The paper also revealed conflicts of interest in many of the studies - due to financial links with baby formula manufacturers.
Dr Robert Boyle, senior author of the study from the Department of Medicine at Imperial College London, said that top brands - such as Aptamil Comfort and SMA Comfort - would offer no protection for babies at risk of allergy.
He said: "Despite parents being advised these hydrolysed milk formulas may reduce the risk of conditions such as milk allergy and eczema, we found no evidence to support these claims."
Dr Boyle said the new study of more than 19,000 participants was the most complete and robust assessment to date.
He added: "Not only did we find no evidence of reduced risk from hydrolysed formula, but we found very few studies which were methodologically sound and without a conflict of interest.
"For instance, in some of the studies all babies were started on the formula at birth, or a few days after. This raises questions about whether enough was done to promote breastfeeding to the mothers in those studies."
Professor Jo Leonardi-Bee, senior statistician on the study from the Division of Epidemiology and Public Health at the University of Nottingham, added: "Our research suggests that there was evidence of publication bias, where some studies that showed formula milk didn't actually reduce allergies may not have been published."
Helen Messenger, spokeswoman for Aptamil, said: "We always welcome new research and will study this report carefully. Aptamil Comfort is for babies with constipation and colic, it's not intended to prevent allergies."
Professor Mary Fewtrell of the Royal College of Paediatrics and Child Health said: "All mothers should be encouraged and supported to breastfeed, whether or not their infant is at risk of allergy.
"Current advice is that infants who are at risk of allergy and who are not exclusively breast-fed should receive a hypoallergenic formula rather than a standard formula.
"However, this new review of the evidence suggests that there is no consistent advantage to using a hypoallergenic formula over a standard formula for preventing the development of allergy.
"Current advice may therefore need to change, and this is currently being reviewed by the Food Standards Agency."