Contributing: Jessica Berman
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, asthma
and other autoimmune disorders.
There are more than eighty disorders where cells that normally defend the body
instead attack tissues and organs. They include rheumatoid arthritis, which
attacks the joints; Crohn's disease, an inflammatory bowel condition; and
juvenile diabetes. Hay fever, a common allergy, is also an autoimmune disorder.
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 hypothesis." They proposed that the
increasing use of antibacterial soaps and other
products, especially early in life, could weaken
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 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
was caused by so-called killer 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 to us was the fact that
once the education event provided by the microbes occurred in early life, it was
durable and lasted throughout the life of the animal."
Rates of autoimmune disorders are rising worldwide, but mostly in wealthier,
RICHARD BLUMBERG: "I think one obvious question, for example, that’s raised
by these studies is the early life use of antibiotics and whether we need to be
more careful in their prescribing."
Rob Dunn is a professor of ecology and evolutionary biology at North Carolina
State University in Raleigh. He says the new study does not mean people should
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.