Treating pregnant mothers, and then their infants, with select strains of probiotics -- bacteria present naturally in the body and sometimes added to food or dietary supplements to boost immune function -- may help prevent a skin condition known as eczema in children with a family history of allergies, particularly during the first 3 months of life, Dutch researchers report.

Eczema is an inflammatory skin condition thought to be related to allergies. Researchers gave more than 150 pregnant women with a family history of allergic diseases either a mixture of three probiotic bacteria or a placebo - inactive pill - during the last six weeks of pregnancy. They also gave the same treatment to the women's children for 12 months.

Neither the women nor their doctors knew whether they were receiving the probiotics or inactive pills.

They were able to follow up with 102 of the children born to the mothers who took part in the study. During the first 3 months of life, the parents of six in 50 of the subjects who received probiotics reported eczema in their children, compared to 15 or 52 of the placebo group, according to a report of the study in the journal Allergy.

Although the rate of eczema in the two groups became more similar, there was still some benefit after for up to two years.

Put another way, it would be necessary to treat approximately 6 mothers and children to prevent one case of eczema at the age of three months and 12 months, and closer to 7 children at two years.

One of the paper's 9 authors is employed by Winclove Bio Industries B.V., Amsterdam, which manufactures the probiotic supplements used in the study.

Allergy 2009;64:1349-1358.