The children of mothers who ate a lot of peanuts while pregnant may be at an increased risk of developing an allergy to the nut - and the more peanuts the mothers ate, the greater the chances, a study found.

But it still is not yet clear if a mother's consumption of peanuts can cause the serious allergy, which appears to be on the rise, affecting about 1 per cent of children.

Scott Sicherer of Mount Sinai School of Medicine in New York City and a team of colleagues at five locations across the United States studied more than 500 infants between three and 15 months old who possibly had a milk or egg allergy but no known peanut allergy. Most had not yet tried peanuts.

The study, published in the Journal of Allergy and Clinical Immunology, found more than a quarter had a strong reaction in a peanut sensitivity test, with children of mothers who had consumed peanuts in pregnancy having nearly three times the odds of showing this potential indication of an allergy.

The more peanuts a woman ate while pregnant, the greater her child's chance of a positive test - although consuming peanuts while breastfeeding did not appear to have a significant impact.

Sicherer and his team noted that the research did not show a clear cause and effect relationship, and that the children in the study only underwent blood tests for peanut sensitivity, which isn't the same as an allergy diagnosis.

His team is continuing to follow the children to determine what allergies might come and go.

The lack of clarity on the issue has left many women confused.

"I have had mothers say they ate a lot of peanuts and think they caused a peanut allergy, and I have had other mothers say they avoided and wonder why their child has an allergy," Sicherer says. "I think that we unfortunately have to say that we do not yet know a certain answer. But the good part of that conclusion is that mothers should not necessarily have a guilty feeling about their past diet decisions."

Guidance has varied over the past decade. The American Academy of Paediatrics issued a recommendation in 2000 that women consider avoiding peanuts during pregnancy and breastfeeding if one of the parents or a sibling had allergies, but withdrew it in 2008.