Feeding infants fish before they reach nine months of age may help reduce their risk of developing eczema, a Swedish study suggests.

The prevalence of eczema in infants has increased in developed countries over the last few decades, and diet is thought to play a role, the researchers said.

To learn more, Dr. Bernt Alm, a pediatrician at the University of Gothenburg in Sweden and his colleagues tracked the long-term health of nearly 17,000 babies born in 2003.

The researchers analyzed responses from more than 4,900 parents who filled in questionnaires about diet and their home environments when the child was six months old and 12 months old. The team also checked medical records.

At six months, 13 per cent of families said their son or daughter had developed eczema, which rose to 20 per cent by the first birthday.

Introducing any type of fish before the baby reached nine months seemed to cut the risk of developing eczema by 25 per cent, the researchers reported in Thursday's online issue of the Archives of Disease in Childhood.

"The fact that fish is rich in omega-3 fatty acids could partly explain the effects found in this cohort," the study's authors wrote.

But no differences were measured between children who ate whitefish or varieties that are richer in omega-3s.

Children with a sibling had nearly twice the risk of eczema, and the risk was also higher if a mother had the skin condition.

Breastfeeding, the age when dairy products were introduced, and keeping a furry pet had no detectable effect, the researchers said.

The Canadian Pediatric Society recommends not introducing solids before six months of age. Some gastroenterologists and pediatric allergists suggest starting at four to six months.