JAMA Report: Children, Pets, & Allergies

For report, visit:
http://jama.ama-assn.org/issues/v288n8/rfull/joc02287.html

{Please keep all of these links bookmarked and next time you hear the
staple excuse "My child's allergic" you will have up-to-date info to
pass on. One less excuse for animal dumpers to use!}

http://www.cbsnews.com/stories/2002/08/27/earlyshow/health/health_news/main519978.shtml

Study: Pets Halt Allergies In Infants
NEW YORK, Aug. 28, 2002

(CBS) Conventional medical wisdom has always assumed that the
presence of pets puts children at a higher risk of developing
allergies.

But more and more evidence is proving that the opposite is true.
Children raised in a house with two or more dogs or cats during the
first year of life may be less likely to develop allergic diseases as
compared with children raised without pets, according to a study in
the latest issue of the Journal of the American Medical Association.

Dr. Dennis Ownby, the chief investigator of the study printed in
JAMA, explains on The Early Show that allergists were trained for
generations that dogs and cats in the house were bad because they
increased the risk of kids becoming allergic to them. The views were
based on the knowledge that before you become allergic to something,
you have to be repeatedly exposed to it.

The latest study, he says, finds that the reverse seems to be true.
Children who grow up with dogs and cats in the home have a
significantly reduced risk of developing pet allergies — plus common
ones, like allergies to pollens and molds — by as much as 50 percent
or more.

This study followed hundreds of children from birth to nearly age 7.
Ownby says that he and his researchers simply started looking at
their data to see if exposure to dogs and cats really increased the
risk of allergies. The data generated surprised researchers because
it concluded that pets gave the opposite reaction. However, the
findings only applied to infants exposed during their first year of
life, when the immune system is still developing.

The researchers think that exposure to dogs and cats leads to lower
risks of allergies because children living with these animals are
probably exposed to higher levels of endotoxins, the breakdown
products of bacteria commonly found in the mouth of a cat or dog.
Exposure to endotoxins is thought to force the body's immune system
to develop a different pattern of response that makes you less likely
to become allergic.

Immediate allergic reactions are caused when immunoglobulin E, a
class of antibodies that causes allergic responses, become bound to
mast cells, a type of white blood cell. This coupling is needed
because antibodies recognize allergens but it's the mast cells that
release histamines and other chemicals that cause allergic symptoms,
the most rapid type of immune response. The result can be swelling,
redness and itching within minutes. But there are checks and balances
within the immune system, and allergic sensitivity can also be
regulated by other portions of the immune system.

Ownby theorizes that early exposure to endotoxin activates a down-
regulatory portion of the immune system, reducing the risk of
allergies. He notes that several studies in this country and others
have provided the first bits of evidence suggesting that exposure to
animals may reduce a child's risk of allergies. For example, studies
in Germany and Switzerland have shown that city dwellers' children
have higher rates of allergies than children of farmers.

The Opposite Reaction

The children in the study were born between 1987 and 1989 to largely
white, middle-class parents who were members of a large, Midwestern
health maintenance organization. The study was funded by the National
Institutes of Health. Doctors followed a group of 474 healthy babies
in the Detroit area from birth to about age 7, comparing the 184
exposed during infancy to two or more dogs or cats to the 220 who
were not exposed to these animals.

When the children were one year old, the researchers contacted
parents by telephone to find out how many pets were in the home. When
the children were two years old, researchers measured the level of
dust mite allergen in their bedrooms. When the children were six or
seven, the researchers tested them for allergic antibodies to common
allergens by two approaches — a skin prick test and a blood
measurement. Allergies usually do not develop until children are
older.

They found that the children exposed to two or more indoor pets were
half as likely to develop common allergies. Children exposed to two
or more dogs or cats during the first year of life were on average 66
to 77 percent less likely to have any allergic antibodies to common
allergens, as compared with children exposed to only one or no pets
during their first year.

Both girls and boys with pets had fewer positive skin tests than
those without to common indoor allergens (dust mite, cat and dog) and
outdoor allergens (grass, ragweed and Alternaria, a fungus found in
air). The reduction remained significant even after adjusting for
risk factors such as older siblings, parental history of asthma and
parental smoking. Also, fewer of the children who had early exposure
to indoor pets had hyper-responsive and easily irritated airways, a
risk factor for asthma. Reactivity was based on the airway's response
to a chemical stimulant called methacholine. Children raised with two
or more dogs or cats had 45 percent less hyper-reactivity. The boys
experienced an even greater reduction of asthmatic symptoms than
girls. About 7 percent of the children developed asthma during the
study, which is on par with national averages.

The results were exactly the opposite of what Ownby and his team
would have predicted from the beginning, and the study is a
significant contribution to the mounting evidence that the things
allergists have believed for years and parents have lived by are
wrong. The striking finding here is that high pet exposure early in
life appears to protect against not only pet allergy but also other
types of common allergies, such as allergy to dust mites, ragweed,
and grass. Other studies have suggested a protective effect of pet
exposure on allergy and asthma symptoms but generally have looked
only at whether pet exposure reduced pet allergy. This new finding
changes the way scientists think about pet exposure.

Scientists must now figure out how pet exposure causes a general
shift of the immune system away from an allergic response.

Some of the Study Findings

Cat allergies: 15.5 percent of the children without a dog or cat in
the home were allergic to cats, compared to 11.6 percent with one cat
or dog and 7.7 percent with two or more pets in their home.

Dog allergies: 8.6 percent of the children without a dog or cat in
the home were allergic to dogs, compared to 3.5 percent with one cat
or dog and 2.6 percent with two or more pets in their home.

Atopy (positive test to any of several common allergens including
cat, dog and grass): 33.6 percent of children were allergic without
exposure to dogs or cats, compared to 15.4 percent allergic with
regular exposure to two or more of the animals. The exception here
was a slight increase in allergies - from 33.6 to 34.3 percent - for
children exposed to only one dog or cat.

Society Too Sterile?

The bottom line is that maybe part of the reason we have so many
children with allergies and asthma is we live too clean a life. When
kids play with cats or dogs and the animals lick them, the transfer
of bacteria may be changing the way the child's immune system
responds in a way that helps protect against allergies. Parents
should not be concerned about having pets in the home with a new baby
but the findings do not go far enough in allergy prevention to
warrant the purchase of pets.

Perhaps one day, scientists might be able to develop a new allergy
therapy based on future research on pets and their bacteria.

© MMII, CBS Worldwide Inc. All Rights Reserved.

Posted on SHARE Yahoo group Aug 30, 2002