Too much mother's milk can increase allergy risk, study shows

Breastfeeding babies gives them the best start in life - but too much of a good thing may make them more prone to allergy, a study has found.

Babies fed exclusively on mother's milk for up to six months are known to be at reduced risk of allergies such as eczema and asthma.

But new research has shown that extending exclusive breastfeeding beyond six months may increase the risks.

The research was started 20 years ago when scientists at the Helsinki Skin and Allergy Hospital in Finland asked 200 mothers to breastfeed their newborns for as long as possible.

The children were assessed for allergies at the ages of 5, 11 and 20. Feeding children exclusively on breast milk for nine months or more appeared to increase their risk of developing allergic conditions such as eczema and food hypersensitivity, according to New Scientist magazine.

At age 5, more than half of children with a family history of allergy who had been breastfed for at least nine months were showing allergic symptoms compared with one-fifth of those who had been breastfed for between two and six months.

The researchers noted that children who developed allergies after prolonged exclusive breastfeeding were most likely to do so during the first years of life.

This suggested that environmental factors such as pollen exposure, diet and disease play a more important role in the onset of allergies in later childhood and adulthood.

Over-exposure to breast milk may provide too much early protection against these triggers.

"A beautiful hypothesis is that there is a time window when the immune system needs to be exposed to external antigens [foreign proteins] for it to develop properly," said researcher Maria Pesonen.

A separate study shows breastfed babies cope better with stress in later life than bottle-fed infants.

The study of 9000 children, published in the Archives of Disease in Childhood, found that children who had been breastfed were more likely to cope well with traumatic events such as their parents divorcing.

Researchers said the benefit could result from the close mother-child bonding as well as calming effect of the hormone leptin in breast milk.

- INDEPENDENT