MONDAY, Dec. 7 (HealthDay News) -- Children born to mothers exposed to
microbes during pregnancy may be less likely to develop allergies, German
researchers say.

They found that pregnant mice exposed to inhaled barnyard microbes gave
birth to allergy-resistant offspring. The microbe exposure triggered a
mild inflammatory response in the mothers. This response was characterized
by increased expression of microbe-sensing Toll-like receptors (TLRs) and
the production of immune molecules called cytokines.

The study was published online Dec. 7 in the Journal of Experimental
Medicine.

The researchers said the mothers' TLRs are essential for transmitting
allergy protection to their offspring, but it's not known how the TLR
signals translate into allergy resistance in the mice pups.

In addition, further investigation is needed to determine whether this
mother-to-offspring protection applies to a wide range of allergens,
including those found in food, said the team at the Phillips-University of
Marburg.

Previous research has shown that children raised on farms -- which teem
with environmental microbes -- develop fewer allergies than those raised
in cities or in non-farming rural areas. One theory is that early-life
exposure to microbes conditions a young child's developing immune system
to tolerate microbes and allergens later in life.

But it may not be a child's exposure to microbes that protects against
allergies. Studies have found that children of farming mothers are also
less susceptible to allergies, regardless of the child's own exposure to
microbes. This new study reveals a biological mechanism that helps explain
this phenomenon.

More information

The Asthma and Allergy Foundation of America has more about allergies.