Children in
their first year of life who live with two or more cats or dogs have less
chance of having common allergies later in life, a new study has found.
Kids raised
with pets were only 31 percent as likely as children without pets to show
common allergic responses by the time they were ages 6 to 7.
The exact mechanism
accounting for this difference is not yet understood, however, according
to lead researcher Dennis R. Ownby, professor of pediatrics and medicine
at the Medical College of Georgia.
It is only
hypothetical, Ownby said, but it may be that early exposure to certain
types of bacteria residing in the digestive tract of cats and dogs -- such
as Lactobacillus -- could affect development of a child's immune system.
The part of
the immune system regulating overall responses when it detects certain
invaders in the body might learn to tone down its response if in frequent
contact with pet-borne bugs, thereby reducing allergic reactions, he said.
"If additional
research supports this work, then it's worth looking at the question on
a molecular basis. Is there something in these bacteria that we could separate
out and give to children ... in their first year of life that will produce
this same effect?" Ownby said.
Although some
recent research tends to support the new finding, the medical community
long has believed exposure to that cats and dogs in the first year could
lead to allergies.
The study,
appearing in the Aug. 28 issue of the Journal of the American Medical Association,
was completed by the Georgia scientists working with researchers in Detroit
at the Henry Ford Health System and Wayne State University. In all, the
team studied 474 children in suburban Detroit from birth through ages 6
to 7.
In the first
year, investigators recorded the parents' allergic history, smoking habits
and the numbers of siblings and pets. At age 2, allergens were collected
from the homes and children tested for exposure to tobacco smoke. At ages
6 to 7 the children were tested for allergic reactions to cats, dogs, dust
mites, ragweed and blue grass.
After statistical
adjustments were made for parental asthma, allergies, smoking and the presence
of siblings, the researchers concluded, "Exposure to two or more dogs or
cats in the first year of life may reduce subsequent risk of allergic sensitization
to multiple allergens during childhood."
If correct,
the findings would fit with a controversial notion called the "hygiene
theory" that states widespread protection against infection in modern cultures
results in underdeveloped immune systems. For example, some studies have
found prolonged exposure to farm animals also is correlated with fewer
allergies.
Robert L. Roberts,
associate professor of pediatrics at the David Geffen School of Medicine
at the University of California at Los Angeles, who specializes in allergy
immunology, told UPI, "The results are probably correct as far the numbers
go." However, Roberts cautioned, "There is a danger, because we don't really
know what the mechanism is, in telling parents '(to) avoid allergies, get
two or more dogs or cats.' If a child is allergic to these, you'll have
more trouble later."
Although acknowledging
that the study appears solid and had adjusted for parental allergies, pediatric
allergist Peyton Eggleston shared some of Roberts' concerns.
"We really
need to see if these results can be repeated independently," Eggleston,
a professor of pediatrics and head of the pediatric allergy program at
Johns Hopkins Children's Center in Baltimore, told UPI. "As a practitioner,
I have concerns about parents thinking that they should rush out and get
a pet to protect their child.
Ten (percent)
or 15 percent of children in this study became allergic to the pet, and
the family then faces the issue of removing the pet for their child's health."
Exposure to
some bacteria in the gut of cats and dogs might reduce allergies, according
to Pedro Avila, an assistant clinical professor of medicine and pediatrics
at the University of California at San Francisco. "There are even trials
now of giving Lactobacillus to pregnant women and to newborns in the first
month of life.
Preliminary
results show that may decrease the incidence of allergies," Avila, who
specializes in allergies and immunology, told UPI.
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