Babies who are born in the autumn are at a greater risk of developing food allergies, experts said today.
Those born in October and November are almost twice as likely to show a form of food intolerance by the age of four, than those born in June and July.
Some 9.5 per cent of autumn babies had an allergic response compared to five per cent of summer babies, the Finnish study found.
Autumn babies were three times as likely to have an allergy to milk and eggs as summer babies.
The researchers believe the variation is due to the foetus's exposure to pollen at a critical time during pregnancy.
At around the end of the third month the foetus begins to produce antibodies.
Pollen appears to trigger the development of a type of antibody known as immunoglobin E, which is well known to be linked to food allergies, wrote the authors of the study, published in the Journal of Epidemiology and Community Health.
Dr Kaisa Pyrhönen, of the Institute of Health Sciences at the University of Oulu in Finland, wrote: "Children having their early gestational period in the pollen season for broad-leafed trees are more prone to sensitisation to food allergens than other children."
Exactly why pollen exposure appears to trigger immunoglobin E remains unknown.
The study looked at 5,920 children born in one region of Finland between Arpil 2001 and March 2006, of which 961 had been tested for food allergies.
George Du Toit, a paediatric allergy consultant at St Thomas' Hospital in London, described the Finnish study as "interesting" but said the findings did not warrant couples trying to time pregnancies to minimise the chance of allergy in their offspring.
The link between seasonal environmental factors and development of antibodies in the foetus remained controversial, he added.
Previous research has shown that babies born in autumn or winter are more prone to eczema and wheezing, identified by higher levels of circulating antibodies to allergens in their blood than those born in spring or summer.
Other studies on the timing of births have indicated that summer babies are more likely to be diagnosed with Attention-Deficit Hyperactivity Disorder (ADHD) and spring babies are more at risk of developing multiple sclerosis in later life.