Cleanliness May Not Be Next to Godliness When it Comes to Allergies, Asthma
Feb. 11, 2000 (Los Angeles) -- Zealous hygiene and a "semisterile"
diet could be contributing to the epidemic of asthma and respiratory allergies
currently afflicting industrialized nations, according to researchers in Italy.
The results of the study support the "hygiene hypothesis," which
proposes that modern practices of sanitation and, possibly, vaccination could
be depriving people of the defenses needed to prevent asthma and allergies.
Allergies affect 40-50 million people in the U.S. and are the sixth leading
cause of chronic disease, according to the American Academy of Allergy Asthma
& Immunology. More than 17 million Americans currently are estimated to
have asthma, which claims more than 5,300 lives each year. Between 1980 and
1994, the prevalence of asthma increased by 75%.
The results of the Italian study support a theory known as the hygiene
hypothesis, which states that modern methods of hygiene and sanitation have
decreased children's exposure to certain microbes in food and water, preventing
them from building defenses to those organisms and increasing their risk of
developing allergies. In a separate study of more than 11,000 young Italian
men, lead author Paolo M. Matricardi, MD, and his colleagues found a direct
correlation between a condition called atopy -- a tendency to develop an
allergic reaction -- and socioeconomic status. Matricardi tells WebMD that
"this positive association is confirmed in other European countries, like
the U.K., and is one of the indirect pieces of evidence supporting the
so-called hygiene hypothesis."
In this study, which appears in the current issue of the British Medical
Journal, Matricardi, research director of the Laboratory of Immunology and
Allergy at the Institute of Experimental Medicine in Rome, and his colleagues
looked at male Italian Air Force cadets aged 17-24. They found that individuals
with more allergies had fewer antibodies to a number of organisms, bacteria,
viruses, and parasites transmitted through food, saliva, or feces, indicating
that they had not been exposed to these organisms. Conversely, asthma was rare
and allergies infrequent among the men who had evidence of antibodies against
at least two of the organisms tested for in their blood.
"These findings are not surprising. There is a growing body of evidence
that things that happen to an infant early in life -- perhaps even in the
uterus -- may influence whether or not that baby becomes allergic," says
Paul Williams, MD, clinical professor of pediatrics and environmental health at
the University of Washington in Seattle. He tells WebMD there is evidence that
other environmental factors, such as early exposure to antibiotics, living in
the city or on a farm, family size, and even birth order may influence a
child's tendency to develop allergies or asthma.
However, Williams, who was not involved in the study, warns that the hygiene
hypothesis is far from proven. "There is suggestive evidence that
intestinal bacteria [that can be transmitted by mouth] influence the
development of allergies, but no firm conclusions can be drawn yet." To
minimize the chances of a child developing allergies, he encourages women to
breastfeed, as this promotes the establishment of normal bacteria in the baby's
intestinal tract, and recommends more judicious administration of antibiotics