Friendly bacteria may halt allergies in babies

A clinical study from Finland

Giving soon-to-be mothers and newborns doses of friendly lactobacilli- bacteria may help prevent childhood allergies, according to findings published in The Lancet. The results are preliminary, but allergy experts say they offer the first good evidence that harmless bacteria can train infants' immune systems to resist allergic reactions.

Researchers at the Turku University Hospital Finland, used a type of bacteria found naturally in the gut, called Lactobacillus rhamnosus, to try to prevent allergy development in at-risk infants. Cultured bacteria that can potentially promote health are called probiotics. Such cultures are found in certain foods like yogurt and cheese.

In this case, Dr. Marko Kalliomaki and his colleagues gave a group of pregnant women probiotic capsules every day for a few weeks before their due dates. For 6 months after delivery, women who breast-fed continued on the probiotics, while bottle-fed infants were given the treatment directly. All of the babies were considered to be at high risk of developing allergies because a parent or sibling was affected.

Excellent results

By the age of 2 years, 35% of the children (46 of 132) had developed allergic eczema, a condition in which the skin becomes irritated, red and itchy. But children who had received probiotics were half as likely to develop the skin condition, . This cut in eczema risk is the "most spectacular, single result" to come out of studies on preventing allergic disease, Dr. Simon H. Murch of Royal Free and University College School of Medicine in London, UK, said in an interview.

Exactly why friendly gut bacteria might protect against allergies is unclear, but the effect may be an "extension of the hygiene hypothesis." This hypothesis holds that the worldwide growth in allergic disease is in part due to our increasingly sterile surroundings. When babies are exposed to germs early on, some experts suggest, their immune systems are steered toward infection-fighting mode, and away from the tendency to overreact to normally benign substances. Support for this idea comes from studies showing that infants who have more colds and other infections have lower asthma rates later in life.

The results of this study suggest that intestine-dwelling bacteria may also play an important role in pushing the immune system away from allergic reactions, the Finnish researchers explain. But how gut bacteria might do this is unclear, noted Dr. Andrew Liu, a pediatric allergy specialist at National Jewish Medical and Research Center in Denver, Colorado. Also unknown is whether these friendly bacteria or infection-causing germs are more important in cutting allergy risk. Still, Liu said the findings are "quite exciting," in part because probiotic treatment seems harmless. And although the treatment has so far shown effects only on eczema, Liu noted, eczema is often an indicator of a child's later asthma risk.

Kalliomaki M, Salminen S, Arvilommi H, Kero P, Koskinen P, Isolauri E. Probiotics in primary prevention of atopic disease: a randomised placebo-controlled trial. The Lancet 2001;357:1076-1079.