When pregnant or breastfeeding mothers take "good bacteria" in the form of probiotics, or give it to their infants, the child's risk of the itchy skin condition eczema may be reduced, a new research review suggests.
But the probiotic supplements do not seem to help prevent any other allergic conditions, researchers found.
"There is a common opinion among clinicians that probiotics may prevent/modulate allergic diseases, but that the effect is rather marginal," said Dr. Philippe Eigenmann of the Paediatric Allergy Unit at University Hospitals of Geneva in Switzerland, who was not involved in the study.
Other such analyses of existing research, known as meta-analyses, have had similar findings, he said.
Read: Fight eczema with pre and probiotics
40% lower risk of eczema
The new meta-analysis was published in the Journal of Allergy and Clinical Immunology. Dr. Carlos A. Cuello-Garcia of McMaster University in Hamilton, Ontario and colleagues reviewed 29 randomised controlled trials of probiotic use and allergies published through the end of 2014.
The trials tested any probiotic formulation, including capsules, oil droplets and suspensions.
In trials involving women who took probiotics during the last trimester of pregnancy, there was a 29 percent decrease in eczema risk among their children.
Trials involving women who took the supplements while breastfeeding found more than a 40 percent decrease in children's risk.
Eczema, marked by red, swollen, itchy skin, can be caused by allergies, and is usually treated with corticosteroids applied to the skin or antihistamines taken in pill form.
In other studies included in the analysis, giving probiotics directly to infants reduced their risk of eczema by about 20 percent.
But probiotic use by mothers or babies was not linked to a lower risk of other allergies, or asthma.
Even the evidence for use among pregnant women and infants was weak, the authors write, since the trials often relied on indirect evidence and the results were inconsistent.
Read: The benefits of probiotics
Early contact with microorganisms boosts immunity
Early contact with microorganisms can help to prevent allergic diseases, Eigenmann said, probably because the immune system learns to tolerate common bugs rather than react against them.
"There are many previous evidences of the efficacy of some probiotic strains in preventing atopic eczema, when administered to the pregnant woman, the newborn or both," said Dr. Enzo Madonini, scientific director at Allergopharma S.p.A, a unit of the pharmaceutical company Merck in Rome, Italy. Merck makes probiotic supplement products.
Madonini was not part of the new review.
Microbiota and probiotics can modulate the immune system, he told Reuters Health by email. Parents who both have allergic conditions should consider giving their infants probiotics, he said.
But, "not all the strains have the same properties and you cannot extrapolate the results with one strain to other strains," he said. "At this moment is difficult to suggest a specific strain."
The studies of probiotics so far have not all been uniform, and there are many key points still to be clarified, he said.
Breastfeeding itself helps protect against developing allergies in childhood, Madonini noted.
The European Academy of Allergy and Clinical Immunology and the American Academy of Allergy Asthma and Immunology do not recommend that pregnant women or infants take probiotic supplements, Eigenmann said, but it is widely recommended in some countries, like Finland.
In South Africa probiotics quite drastically in price, however you should be able to find some for around R50.00 at your local pharmacy.
Source: Journal of Allergy and Clinical Immunology June 1, 2015.
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