Treating infants orally with extracts from bacteria apparently reduces the risk that they will develop eczema--but the treatment doesn't work if both parents have a history of atopy, a group of scientists from Germany and the Netherlands recently found.
It's been known for a while that exposure to certain microbes, particularly on farms, seems to protect children against eczema to some degree. The microbes must contain, or be coated in, some active compounds that cause the immune system to develop tolerance; researchers have identified a number of classes of compounds, including those called lipopolysaccharides and peptidoglycans. In this recent trial, involving over 600 subjects, the scientists used whole-cell extracts from heat-inactivated Escherichia coli and Enterococcus faecalis. They asked parents to dose their kids three times daily from the age of 5 weeks to 7 months.
Parents were selected for the trial if one or both had a history of eczema, asthma, or allergic rhinitis. Overall, the treatment had no effect on whether or not the children developed eczema. However, when the scientists considered children who only had one parent with atopy, the treatment reduced the kids' chances of developing eczema from 19% to 10% (measured right at the end of the trial; the improvement was lasting, up to three years out). The effect was even more pronounced if it was the dad, rather than the mom, who was atopic; the risk dropped from 32% to 11%.
Now I'd like to know why the children of atopic dads had a 32% chance of getting eczema, versus 19% for children who had either an atopic mom or dad. I can't find an explanation in the paper.
Instead, the authors focus on why the improvement was weaker in the atopic either-mom-or-dad group. They suggest that this is because a fetus's immune system depends not just on its genetics but also a heavy imprint that the fetus receives from the mother during pregnancy. If the mom is atopic, dosing the infant with bacteria after birth has less influence on whether he or she develops eczema. If the dad is atopic, the medicine has a stronger effect.
This seems contradictory to me; if the maternal imprint has a major effect, the children of parents of whom only the mom is atopic should be more likely to develop eczema than the children of parents of whom only the dad is atopic. The authors say that this is indeed the fact, but their own paper has it the other way around.
The inactivated-bacteria therapy is well-documented as safe, the authors say; it has been used to treat irritable bowel syndrome. In this trial they saw very few adverse reactions.
Do you think that parents of newborns would be likely to use this treatment on their kids? I wonder. Only if you've lived with severe eczema, or already had a child with it, or seen it close up, would you be motivated at the very difficult early months to try to give your kid medicine. And you could say it roughly halves the chances of developing eczema, but in truth, it reduces it from 20% to 10%. If this study is true, that's what you get for six months of giving your kid medicine three times a day. Would you do that if only one parent had hayfever?