Helping the body discover which germs are harmless.


Ask mothers why babies are constantly picking things up from the floor or ground and putting them in their mouths, and chances are they¡¯ll say that it¡¯s instinctive? that that¡¯s how babies explore the world. But why the mouth, when sight, hearing, touch and even scent are far better at identifying things?

Since all instinctive behaviors have an evolutionary advantage or they would not have been retained for millions of years, chances are that this one too has helped us survive as a species. And, indeed, accumulating evidence strongly suggests that eating dirt is good for you.

In studies of what is called the hygiene hypothesis, researchers are concluding that organisms like the millions of bacteria, viruses and especially worms that enter the body along with¡°dirt¡±spur the development of a healthy immune system. Several continuing studies suggest that worms may help to redirect an immune system that has gone awry and resulted in autoimmune disorders, allergies and asthma.

These studies seem to explain why immune system disorders like multiple sclerosis, Type 1 diabetes, inflammatory bowel disease, asthma and allergies have risen significantly in the United States and other developed countries.

¡°What a child is doing when he puts things in his mouth is allowing his immune response to explore his environment,¡±Mary Ruebush, a microbiology and immunology instructor, wrote in her new book,¡°Why Dirt Is Good.¡±¡°Not only does this allow for¡®practice¡¯of immune responses, which will be necessary for protection, but it also plays a critical role in teaching the immature immune response what is best ignored.¡±

One leading researcher, Dr.Joel V.Weinstock, the director of gastroenterology and hepatology at Tufts Medical Center in Boston, said in an interview that the immune system at birth¡°is like an unprogrammed computer. It needs instruction.¡±

He said that public health measures like cleaning up contaminated water and food have saved the lives of countless children, but they ¡°also eliminated exposure to many organisms that are probably good for us.¡±

In answer to the question,¡°Are we too clean?¡±Dr.David Elliott, a gastroenterologist and immunologist at the University of Iowa, said: ¡°Dirtiness comes with a price. But cleanliness comes with a price, too. We¡¯re not proposing a return to the germ-filled environment of the 1850s. But if we properly understand how organisms in the environment protect us, maybe we can give a vaccine or mimic their effects with some innocuous stimulus.¡±

Dr. Ruebush deplores the current fetish for the hundreds of antibacterial products that convey a false sense of security and may actually foster the development of antibiotic-resistant, disease-causing bacteria. Plain soap and water are all that are needed to become clean, she noted.

¡°I certainly recommend washing your hands after using the bathroom, before eating, after changing a diaper, before and after handling food¡± and whenever they¡¯re visibly soiled, she wrote. When no running water is available and cleaning hands is essential, she suggests an alcohol-based hand sanitizer.

Dr.Weinstock goes even further.¡°Children should be allowed to go barefoot in the dirt, play in the dirt and not have to wash their hands when they come in to eat,¡±he said. He and Dr.Elliott pointed out that children who grow up on farms and are frequently exposed to worms and other organisms from farm animals are much less likely to develop allergies and autoimmune diseases.