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Respiratory allergies such as hay fever and asthma are increasing
on a global scale. In Western Europe, the prevalence of asthma
is reported to have doubled in the last ten years, while allergies
in general are also on the increase. One striking feature is the
geographical variation in allergy prevalence in Europe –
major international studies focusing on asthma and allergies in
children have found a 20-fold difference between various European
centres, the reasons for which remain to be explained.
Cause and effect
Allergy is an over-reaction of the immune system to a substance
it perceives as 'foreign'. Outdoor air pollution aggravates respiratory
allergies and is suspected of causing allergies. They are, indeed,
more prevalent in large cities than in rural areas, and workers
experiencing chronic exposure to gases, fumes, and biological
and mineral dusts are particularly susceptible. Yet prevalence
of asthma and allergy does not correlate precisely with air pollution
levels in different cities.
The indoor environment seems to play an important role. Warm
homes with soft furnishings and carpeting tend to have high levels
of allergy triggers, such as dust mites, pet fur, moulds, damp
tobacco smoke, and gas heater fumes. There are also suggestions
that infants raised in a very hygienic environment are more allergy-prone
in later life than those brought up in contact with dirt, animals,
and other children. Early exposure to certain bacteria may actually
protect us against allergies.
KA4 investigates
Research is needed to unravel the genetic, environmental, dietary,
lifestyle and medical causes of allergies. To achieve this, projects
are exploiting the European diversity of lifestyles and environments.
By means of surveys, pollutant measurements, clinical studies,
and DNA banks, European researchers are seeking the keys that
will access better allergy prevention.
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Particles and
allergy
There are major differences in the prevalence
of respiratory allergies across Europe. As small
airborne particles appear to be important contributing
factors here, the RAIAP project1 is addressing
the question: "Do qualitative differences
in particulate air pollution at different locations
explain differences in the prevalence and severity
of respiratory allergies?"
The partners are collecting particulate samples
from Lodz, Oslo, Rome, Amsterdam, and a Dutch
coastal location. They will examine the particles
to determine their physico-chemical characteristics
and to see whether known antigens or inflammatory
agents are bound to them. The team will then
test the allergic and inflammatory potential
of the samples in model systems and try to clarify
the mechanisms by which particles modulate inflammatory
or immune responses.
A final report will review the latest knowledge
and will point to possible preventive measures.
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Respiratory allergy and inflammation due to ambient
particles – a European-wide assessment:
QLK4-2000-00792 |
Prof. Erik Dybing
National Institute of Public Health, (NO)
Erik.dybing@folkehelsa.no
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Under surveillance
In 1992-93, more than 10 000 young adults living
in 24 countries, mainly in Europe, were selected
at random from population registers to take
part in a cross-sectional study of asthma and
allergic disease. Questionnaire data provided
information on respiratory symptoms, diagnosed
asthma and its treatment, smoking, occupation,
and housing (including the presence of pets
and gas appliances) and other environmental
factors. Participants in the study underwent
lung function tests and provided blood samples
for serum markers for allergy. The survey demonstrated
large geographical variations in the prevalence
of asthma and allergy. Further analyses identified
associations between environmental factors –
including exposures in the workplace –
and disease.
Today, the nine-year follow-up2 of this study
is under way. Questionnaire data are being collected
and participants are repeating lung function
tests and providing blood samples. These are
being stored in a ‘bank’ to allow
for analysis for candidate ‘susceptibility
genes’, at a later date.
Analysis of the results will show how factors
in indoor, outdoor and professional environments
relate to the incidence and prognosis of allergy
and allergic disease, and will identify factors
which contribute to lung function decline. The
extent to which the effect of such exposures
is influenced by genetic predisposition may
also be examined. |
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European Community Respiratory Health Survey II
(ECRHS II): QLK4-1999-01237 |
Jill Knox
King's College London (UK)
jill.knox@kcl.ac.uk
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Teaching us tolerance
The Allergyflora project3 is focusing on a
group of 300 infants in their first year of
life. Partners are identifying the bacteria
that compose the intestinal microflora of such
a group, and are collecting data on family size,
day care, housing conditions, and indoor and
outdoor air pollution (at recruitment stage),
and on feeding practices, vaccinations, day
care, illnesses and medications (during the
study). They will screen the children for signs
of allergy at one-and-a-half and three years
of age, and parents will supply additional information
via a questionnaire.
The idea is that certain groups of intestinal
bacteria might 'teach' an infant's immune system
not to over-react to the presence of innocuous
antigens, and that the absence of these bacteria
would result notably in the development of allergies.
Extreme hygiene could account for the absence
of these key bacteria. If this hypothesis is
proved to be correct, it may help explain why
allergies are increasing in Europe. This knowledge
may be used in efforts to modify the composition
of the intestinal flora by means of 'probiotic'
foods.
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Impact of intestinal microflora on allergy development:
QLK4-2000-00538 |
Dr Agnes Wold
Department of Clinical Bacteriology (SE)
agnes.wold@microbio.gu.se |
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