As a part of their study the researchers followed 13,889 children who had been selected at birth from 31 Belarussian maternity hospitals in the randomized Promotion of the Breastfeeding Intervention Trial (PROBIT).
The children were then analysed in a follow-up trial in from December 2002 to April 2005, when they were 6-and-a-half years old.
Also taking part in the study was a control group of maternity hospitals and affiliated polyclinics who carried out their traditional practices, while those in the experimental group were trained to teach better breastfeeding techniques and encouraged mums to breastfeed as long and as exclusively as possible.
The researchers however found that breastfeeding did not protect against asthma or allergies.
In fact, the team noted that there was an increased risk of positive allergic skin tests.
"We found, not only was there no protective effect but the results even suggested an increased risk of positive allergic skin tests," The BMJ quoted Dr Kramer, as saying.
However there was some good news, as the researchers found that breastfeeding reduced gastrointestinal infections and atopic eczema for the first year of life.
"In the first phase of our project, we observed reductions in gastrointestinal infections and atopic eczema for the first year of life. I urge mothers to continue to breastfeed," Dr Kramer said.
The study was pre-published online September 11 by the British Medical Journal.