WEDNESDAY, Oct. 20 (HealthDay News) -- The chances of a child developing food allergies may be increased if that child is conceived in the early spring, a preliminary study by Finnish researchers suggests.

Studies have already shown that children born in autumn or winter are more likely to eczema, wheeze and asthma than children born in spring or summer, the researchers noted.

There may be several reasons for this new finding, said lead researcher Dr. Kaisa Pyrhonen, of the Institute of Health Sciences at the University of Oulu, including concentration of pollen in spring, exposure to sunlight, which is related to synthesis of vitamin D, and viral infections.

"These are possible explanations, but our study design did not allow any assessment of the causal role of the above factors," Pyrhonen said.

Pyrhonen said the study findings are preliminary and families should not plan pregnancies around specific times. "Because our study was an observational study, we cannot give any recommendations to families," Pyrhonen said.

The report is published in the Oct. 20 online edition of the Journal of Epidemiology and Community Health.

For the study, Pyrhonen's team collected data on 5,920 Finnish children born between 2001 and 2006. From birth to four years, 961 of these children were tested for food allergies.

Up to age of 4, the odds of having a food allergy varied according to season of birth, ranging from 5 percent for children born in June and July to 9.5 percent for those born in October and November, the researchers found.

In fact, 11 percent of children whose 11th week of development occurred during April or May had food allergies, compared with 6 percent of children who reached that stage of development in December or January, Pyrhonen's group found.

In terms of specific allergies, a child whose first three months of fetal development ended in April or May was three times more likely to be allergic to milk and eggs compared with those who reached that stage in November or December, the researchers said.

Commenting on the study, Dr. Erick Forno, an assistant professor of pediatrics at the University of Miami Miller School of Medicine, said there could be a variety of reasons for this finding.

"But what is important is that we are understanding more that there are environmental factors that at some point during pregnancy play an important role in developing the immune system that predisposes the kid to have either food allergies or environmental allergies or asthma or eczema or something of that sort," he said.

Forno cautioned that this was an observational study (a type of study in which people are observed or certain outcomes are measured and no effort is made to affect the outcome -- for instance, no treatment is given). "So there may be other things that these researchers didn't measure that are also associated. What they are looking at is the common consequence. So we can't say it's a causal association," he said.

Parents need to realize that things outside the uterus are very important in the developing fetus, Forno said, adding, "We are only beginning to understand what goes on."

More information

For more information on allergies, visit the U.S. National Library of Medicine.