The findings, reported in the Journal of Allergy and Clinical Immunology, add to a mixed bag of results from research into whether probiotics can help ward off kids' allergies.
Based on what's known so far, it may be that only certain probiotics are helpful for certain kids - but even then, the benefit seems "very modest," according to Dr. Sonia Michail, a pediatric gastroenterologist at Children's Hospital Los Angeles who was not involved in the work.
The 123 kids in this study, which was led by Marie P. Jensen of the University of Western Australia in Perth, were part of a clinical trial as infants, when researchers randomly assigned half to take a probiotic supplement every day for the first six months of life. The rest of the babies were given a placebo.
All of the babies were considered to be at increased risk of allergies because their mothers suffered from them.
In earlier studies, the researchers found no benefits of the probiotic when the babies were 1 to 2.5 years old.
This latest report finds still no effects at the age of 5. Of 66 kids who had received the probiotic in infancy, 44 percent had some type of allergy - such as nasal allergies, food allergies or asthma. That compared with 38 percent of 57 kids who got the placebo.
Probiotics are live microorganisms, usually bacteria, which are naturally present in the gut, and are often added to certain foods, like yogurt and fermented milk, or sold as supplements.
In theory, probiotics given early in life could help curb kids' allergy risk by ensuring a healthy balance of microbes in the intestines, which promotes normal immune function.
Allergies arise when the immune system overreacts to a normally benign substance.