News and Research
Immune System
Early Fevers Associated With Lower Allergy Risk Later
In Childhood
2-10-2004
Infants who experience fevers before their first birthday
are less likely to develop allergies by ages six or seven,
according to a new study funded by the National Institute
of Allergy and Infectious Diseases (NIAID), part of the
National Institutes of Health (NIH). The study, published
today in the Journal of Allergy and Clinical Immunology,
lends support to the well-known "hygiene hypothesis,"
which contends that early exposure to infections might protect
children against allergic diseases in later years.
"The
prevalence of asthma and allergies has increased dramatically
worldwide in recent years," says Anthony S. Fauci,
M.D., director of NIAID. "This study provides evidence
that diminished exposure to early immunological challenges
could be one of the reasons for this trend."
"The
hygiene hypothesis is widely recognized but largely unproven,"
says Kenneth Adams, Ph.D., who oversees asthma research
funded by NIAID. "The findings of this study strengthen
the hypothesis and, after more research, could lead to preventative
therapies for asthma and allergies."
The
authors of the study followed the medical records of 835
children from birth to age 1, documenting any fever-related
episodes. Fever was defined as a rectal temperature of 101
degrees Fahrenheit or above. At age 6 to 7 years, more than
half of the children were evaluated for their sensitivity
to common allergens, such as dust mites, ragweed and cats.
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Researchers
found that, of the children who did not experience a fever during
their first year, 50.0 percent showed allergic sensitivity. Of
those who had one fever, 46.7 percent became allergy-prone. The
children who suffered two or more fevers in their infancy had
greater protection, with only 31.3 percent showing allergic sensitivity
by ages 6 to 7.
In particular, fever-inducing infections involving
the eyes, ears, nose or throat appeared to be associated with a lower
risk of developing allergies, compared with similar infections that
did not result in fevers.
"We didn't expect fever to relate with such a
consistent effect," says Christine C. Johnson, Ph.D, M.P.H.,
senior research epidemiologist of the Henry Ford Health System in
Detroit, MI, and one of the co-authors of the study. "It also
was interesting that the more fevers an infant had, the less likely
it was that he or she would be sensitive to allergies."
Dr. Johnson says that more research is needed to establish
if early fevers have a direct effect on allergic development in children.
Additionally, she and the other authors are working to determine if
early exposure to pets as well as high levels of bacteria could also
lower allergy risk. "If we can uncover which environmental factors
affect allergic development and why, it may be possible to immunize
children against these conditions," she says.
This study also received support from the National
Institute of Environmental Health Sciences, another NIH component.
NIAID is a component of the National Institutes of
Health (NIH), an agency of the U.S. Department of Health and Human
Services. NIAID supports basic and applied research to prevent, diagnose
and treat infectious diseases such as HIV/AIDS and other sexually
transmitted infections, influenza, tuberculosis, malaria and illness
from potential agents of bioterrorism. NIAID also supports research
on transplantation and immune-related illnesses, including autoimmune
disorders, asthma and allergies.
Reference:
L Keoki Williams et al. The relationship between early
fever and allergic sensitization at age 6 to 7 years. Journal of Allergy
and Clinical Immunology 113(2): 291-296 (2004).
Press
releases, fact sheets and other NIAID-related materials are available
on the NIAID Web site at www.niaid.nih.gov.
This
article has been adapted from a news release issued by NIH/National
Institute Of Allergy And Infectious Diseases, www.niaid.nih.gov.
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