http://news.bbc.co.uk/2/hi/health/8633001.stm
Summer babies have more exposure to vitamin D present in sunlight
Babies born in autumn or winter are more likely to develop a food allergy than those born in spring or summer, US researchers have found.
The Boston scientists believe the trend may be explained by a lack of the sunshine vitamin, vitamin D.
Vitamin D from natural sun exposure is needed for the healthy development of a child's immune system, experts believe.
And winter babies tend to get less sun, they explain in the journal Annals of Allergy, Asthma & Immunology.
The doctors from Massachusetts General Hospital in Boston reviewed all of 1,002 patients with food allergies who had been seen in three local hospital emergency departments over a period of six years.
They then compared the months of birth in patients with food allergy with those of patients visiting the emergency rooms for reasons other than food allergy.
Seasonal effect
From this a trend emerged - allergies appeared to be linked with season of birth, but only in the patients who were aged five or younger.
Of the children treated for allergy aged under five, 41% were born in spring or summer compared with 59% in autumn or winter.
The researchers acknowledge that other factors, such as infections, family history of allergies, maternal and infant dietary patterns, and exposure to indoor pollutants, may contribute to food allergies.
But they believe that vitamin D deficiency, and hence month of birth, "is a significant potential risk factor" in the development of food allergies.
Exposure to low vitamin D levels in the womb, immediately after birth and during early childhood may be key.
Previous studies have associated month of birth with other allergic conditions such as asthma, recurrent wheezing and dermatitis.
Dr Milo Vassallo, lead author of the study and a physician at Massachusetts General Hospital, said: "Vitamin D helps the body fight infection and suppresses its allergy cells.
"When the body is faced with a molecule of food it has to decide if it's a friend or a foe. Vitamin D contributes to tolerance but reduced levels of vitamin D triggers intolerance in the body," he said.
But the researchers stressed the findings did not mean parents should not attempt to boost their child's vitamin intake to ward off allergies.
A spokesperson for the charity Allergy UK said it was an interesting finding but more research needed to be carried out in this area.
She said: "It is unlikely that parents will change the month in which their children are born, but it might give some clues about possible links to the effects that sunlight / vitamin D has on the immune system."
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