Children’s chances of developing allergies to foods such as milk and eggs could depend on when they are conceived, a Finnish study suggests.
Babies conceived in January or February have an 11% risk of becoming susceptible to a food allergy, while those whose life began in utero during September or October have a 6% chance, finds the study, published in the Journal of Epidemiology and Community Health.
The 11th week of gestation was found to be the crucial period. If it occurred during April or May the baby had the greatest vulnerability to getting a food allergy in childhood. The high levels of birch and alder pollen circulating at that time were judged to be possibly responsible. It is around this early stage of development that a foetus starts to produce antibodies to allergens.
“We found a higher incidence of positive results in food allergy tests among children born in October or November than among those born in other months”, said Kaisa Pyrhonen, of the Institute of Health Sciences at Oulu University, in Finland.
The Finnish researchers studied 5,973 children born in the south-east of the country between 2001 and 2006.
Pyrhonen added: “The incidence of such results was particularly high and especially pronounced for milk and egg among children who had their 11th gestational week in April or May, the season during which the concentrations of pollen from birch and alder are highest in the area concerned.”
Allergic diseases such as asthma, hay fever and eczema have become far more common since the 1950s, and doctors and scientists have advanced different theories to explain the rise.
It is estimated that about 5%-6% of children in the UK have an intolerance to at least one food. A House of Lords inquiry in 2008 into allergies found that 39% of children and 30% of adults had been diagnosed with asthma, eczema or hay fever, or more than one of those conditions.
Lee Noimark, a consultant paediatric allergist at Barts and the London children’s hospital in the capital, noted that exposure to sunlight as a child, or lack of it, could also be to blame for the allergies.
Lindsey McManus, of the charity Allergy UK, said that while the findings were interesting, more research was needed, especially into a potential genetic basis of allergies. “Allergies are often passed down in families, and the genetic predisposition to develop allergies is very strong. It would be interesting to see whether parents would be influenced by this research as to when they decide to start a family, but I think more evidence would be necessary.”
The new study is in line with previous research which found that children born in autumn or winter were more likely to suffer from eczema and wheezing.
The Guardian Uk