UPDATE 11.30am: Kids who are given only breastmilk in their first six months have an increased risk of developing an allergy to nuts, research has found.
A joint research project between the Australian National University's medical school and the ACT Health Directorate investigated a link between breastfeeding and nut allergies using information from the parents of children starting primary school in the ACT.
The Kindergarten Health Check Questionnaire asked parents if their child had a nut allergy, and about their baby's feeding habits in the first six months of life.
Researchers said the study showed that rates of nut allergies in children in the ACT were increasing and those who were breastfed were more likely to have a nut allergy.
The study's author, Marjan Kljakovic, said 3.9 per cent of children starting school in the ACT had a parent-reported nut allergy - almost twice the rate of British children.
The likelihood of developing a nut allergy was 1.5 times higher in children who were solely breastfed in the first six months, than in those exposed to other foods and fluids, the Professor of General Practice at the ANU Medical School said.
Protection against nut allergy was found in children who were fed food and fluids other than breastmilk.
"Our results contribute to the argument that breastfeeding alone does not appear to be protective against nut allergy in children - it may, in fact, be causative of allergy," Professor Kljakovic said.
"Over time, health authorities' recommendations for infant feeding habits have changed, recommending complementary foods such as solids and formula be introduced later in life.
"Despite breastfeeding being recommended as the sole source of nutrition in the first six months of life, an increasing number of studies have implicated breastfeeding as a cause of the increasing trend in nut allergy.
"Peanut allergy accounts for two-thirds of all fatal food-induced allergic reactions. It is important for us to understand how feeding practices might be playing a part."
Experts have urged caution about interpreting the study's results, saying it could be that children at higher risk of developing allergies are simply breastfed longer.
Murdoch Children's Research Institute (MCRI) researcher Jennifer Koplin said women were not advised to avoid nuts during pregnancy or breastfeeding.
"There's absolutely no strong evidence that eating nuts while pregnant or breastfeeding will cause allergy," Ms Koplin said.
She said previous studies by MCRI had shown that children at risk of developing allergies were often breastfed for a longer term; for example, if a child showed signs of eczema the mother would be more likely to breastfeed longer in the belief it could help.
MCRI researchers have conducted studies showing that the timing of introducing children to foods such as milk, eggs and nuts could be crucial in reducing the risk of developing allergies.
The Australian National University paper has been published in the International Journal of Pediatrics.