【英语语言学习】全身弄得脏兮兮对孩子健康有益

This is the VOA Special English Health Report.
 
A new study suggests that early exposure to germs strengthens the immune system. That means letting children get a little dirty might be good for their health later in life.
 
The study involved laboratory mice. It found that adult mice raised in a germ-free environment were more likely to develop allergies 1, asthma 2 and other autoimmune disorders 4. There are more than eighty disorders where cells that normally defend the body instead attack tissues and organs.
 
They include rheumatoid arthritis 5, which attacks the joints 6; Crohn's disease, an inflammatory bowel 7 condition; and juvenile 8 diabetes 9. Hay fever, a common allergy 10, is also an autoimmune disorder 3.
 
Richard Blumberg is a professor at Harvard Medical School in Boston, Massachusetts. He says in nineteen eighty-nine, medical researchers sought to explain these diseases with what they called the "hygiene 11 hypothesis." They proposed that the increasing use of antibacterial soaps and other products, especially early in life, could weaken immune systems.
 
RICHARD BLUMBERG: "The hypothesis has stated or suggested that early-life exposure to microbes is a very important determinant of later life sensitivity to allergic 12 and so-called autoimmune diseases, such as hay fever, asthma, inflammatory bowel disease and others."
 
Now, Dr. Blumberg and a team have what they say is the first biological evidence to link early exposure to germs to stronger adult immune systems. They say this exposure could prevent the development of some autoimmune diseases.
 
In the adult germ-free mice, they found that inflammation in the lungs and colon 13 was caused by so-called killer 14 T cells. These normally fight infection. But they became overactive and targeted healthy tissue -- an autoimmune condition seen in asthma and a disease called ulcerative colitis.
 
Dr. Blumberg says the mice raised in a normal environment did not have the same reaction. He says their immune systems had been "educated" by early exposure to germs.
 
RICHARD BLUMBERG: "What was really most remarkable 15 to us was the fact that once the education event provided by the microbes occurred in early life, it was durable 16 and lasted throughout the life of the animal."
 
Rates of autoimmune disorders are rising worldwide, but mostly in wealthier, industrialized countries.
 
RICHARD BLUMBERG: "I think one obvious question, for example, that’s raised by these studies is the early life use of antibiotics 17 and whether we need to be more careful in their prescribing."
 
Rob Dunn is a professor of ecology and evolutionary 18 biology at North Carolina State University in Raleigh. He says the new study does not mean people should stop washing.
 
ROB DUNN: "Wash your hands, but don't do it with antimicrobial soap. Let your kids play in a reasonable amount of dirt and get outside and get exposed to a diversity of things."
 
The study appears in the journal Science.
 
And that's the VOA Special English Health Report. I'm Steve Ember.