Women who take fish oil capsules and probiotics while pregnant could protect their baby from allergies.
Fish oil has been found for the first time to shield against reactions to hen’s eggs and peanuts – which can lead to a deadly anaphylactic shock.
A daily capsule, taken after the 20th week of pregnancy and for the first three or four months of breastfeeding, cuts the chances of a woman’s child developing an egg allergy by almost a third.
A review of 19 fish oil studies, led by Imperial College London, found it may slash a child’s risk of a peanut allergy by 38 per cent.
Researchers also found a daily probiotic supplement could reduce the risk of childhood eczema by more than a fifth.
Fish oil has been found for the first time to shield against reactions to hen’s eggs and peanuts
Fish oil is believed to keep a child’s immune system in check, so it doesn’t flare up in response to food, while probiotics may prevent allergies by regulating bugs in the gut.
Lead researcher Dr Robert Boyle, from Imperial College London, said: ‘Food allergies and eczema in children are a growing problem across the world.
‘Although there has been a suggestion that what a woman eats during pregnancy may affect her baby’s risk of developing allergies or eczema, until now there has never been such a comprehensive analysis of the data.
‘Our research suggests probiotic and fish oil supplements may reduce a child’s risk of developing an allergic condition, and these findings need to be considered when guidelines for pregnant women are updated.’
A hen’s egg allergy is the most common food allergy, above peanuts, and can cause anaphylactic shock, vomiting and difficulty breathing.
Affecting one in 20 children, it is caused by the immune system malfunctioning and overreacting to a harmless food.
Researchers found children whose mothers consumed fish oil capsules had a 30 per cent reduction in their risk of egg allergies by the age of one.
The review also found a 38 per cent reduction in peanut allergy risk, but only in two of the 19 studies.
Peanut allergies are the second most common food allergy, affecting one in 40 breastfed children.
Eczema risk was reduced by 22 per cent in children whose mothers took a probiotic supplement between 36 and 38 weeks of pregnancy, according to the review of 28 trials involving around 6,000 women.
Eczema, also thought to involve an overactive immune response, affects around one in five children in the UK and causes dry, cracked and itchy skin.
The findings come from one of the biggest investigations of maternal diet and childhood allergy ever undertaken. Scientists pooled total data from more than 400 studies involving 1.5 million mothers and their children.
While clear benefits were seen from fish oil and probiotics, there was no evidence that avoiding potentially allergy-triggering foods such as nuts, dairy produce and eggs during pregnancy had any effect.
The new findings appear in the latest issue of the online journal Public Library of Science Medicine.
Commenting on the research, Seif Shaheen, professor of respiratory epidemiology at Queen Mary University of London, said: ‘More definitive answers on the possible role of maternal probiotic and fish oil supplementation in the prevention of childhood allergic disease can only come from further large trials, which follow up the children to school age.
‘If such trials are big enough, they may be able to identify particular subgroups of mothers and children who would benefit most from these interventions.’