In this overview, the evidence used below to make my case for an Allergy Epidemic
is from high quality studies, from peer-reviewed literature. The three main studies
that supports the argument are the International Study of Allergy, Asthma in Children
(ISAAC), the Global Allergy and Asthma European Network (GA²LEN), and one very interesting
objective serologic study looking at increased IgE sensitization, that have shown
an increase in atopy (allergic sensitization).
The first study,
the International Study of Asthma and Allergies in Childhood
is a unique international, questionnaire and video-based
epidemiologic study on allergies, which was established in 1991, and led by Professor
Innes Asher of the University of Auckland. The study started out of concern for
the increasing prevalence of asthma, eczema and rhinitis in Western and developing
countries. This study has become the largest worldwide collaborative study, involving
over 100 countries. The ISSAC findings to date have suggested that these allergic
diseases are increasing more in developed and developing countries. For example,
the Phase 3 of the study which was conducted between 2000 and 2003 and surveyed
children from 233 centres in 97 countries found that the prevalence of wheeze (asthma)
in the past 12 months (current asthma) ranged from 32.6% in Wellington, New Zealand
to 0.8% in Tibet, China in the 13-14 year olds. Also, the study has found that although
the asthma symptoms are more prevalent in more affluent countries, they appear to
be more severe in less affluent countries.
So far the ISAAC study has been unable to find the cause(s) for this increased prevalence
and the wide global variation in asthma prevalence, but they have highlighted some
clues and enough questions for further ongoing studies. Also, even though there
are not a lot of answers, Phase 3 of the study has shown a reduction in the severity
and prevalence of asthma symptoms in 6-7 year-old and 13-14 year-olds in New Zealand,
in the period 2001-2003, when the same age groups were compared to the period 1992-3.
The most likely explanation for this improvement in symptoms in this phase, is improved
awareness that the study as brought about along with better management of asthma
due to national and International Asthma management Guidelines.
The second study,
The GA²LEN study (2)
is a pan-European
multidisciplinary collaboration which was set up in 2005, to increase networking
for scientific projects in allergy and asthma around Europe. The network consists
of 27 research centres, 60 collaborating centres, and 500 researchers in 25 countries.
The aim of the researchers is to become the world leader in the field of allergy
research and to develop and implement allergy guidelines. Its vision is:
all aspects of allergic diseases in order to create a better understanding of allergic
diseases among the general public, patients, health professionals and policy makers".
What they have discovered so far is that:
"Allergic diseases including allergic rhinitis, asthma, rhino-conjunctivitis,
gastrointestinal symptoms, urticaria (hives) and eczema are among the most common
chronic diseases in the world and rank first in Europe. Their prevalence continues
to grow with one child in three now affected by an allergic disease.
indicate that half of all Europeans will suffer from allergy by 2015".
"There is significant under-diagnosis and under-treatment in all areas of allergy,
with the majority of patients left untreated according to existing medical standards."
Some of the epidemiologic questions regarding allergies that GALEN is currently
looking at include:
- Pollution and its effect on allergic sensitization.
Sensitization and symptoms – Understanding the reasons why patients with IgE sensitization
develop allergic symptoms will be crucial to our understanding of the "allergy epidemic".
One of GALEN’s recent studies has shown that only very few of the "asymptomatic"
patients that were sensitized to birch and Parietaria pollen did develop symptoms
when they underwent nasal challenges, when compared with the general (non-sensitized)
- Studies on the interaction between nutrition and allergic immune response.
The third important study
is an objective serologic study showing increasing
prevalence of atopy (3)
. This is one of the few studies where
objective measurements are made to show that the prevalence of allergies (asthma,
eczema and hay fever) have increased over the past 20 – 30 years is a study from
the UK done in 2005. The researchers looked at frozen serum samples of men aged
40 -64 years, who attend the British United Provident Association (BUPA) for routine
medical examinations. One good feature to this study was that all these men were
socioeconomically similar, being all professionals or businessmen. Three groups
of samples (containing 513 each) were matched by age and month of attendance for
1996, 1981, and 1975. The samples were tested for specific IgE sensitization to
11 common inhaled allergens (including cat, grass, house dust mites) and a highly
significant increase in IgE sensitization over time. The average rate of increase
was equivalent to an additional 4.5% of men becoming positive (IgE sensitized) each
decade. This study objectively showed through serological measurements at three
time periods that earlier birth cohorts are less likely to have become atopic than
more recent ones.
Other well designed global studies supporting an Allergy Epidemic
Increasing asthma prevalence in New Zealand
The increasing prevalence of asthma in New Zealand was noted way back in 1989 in
a survey of 435 asthmatic adolescents looking at asthma symptoms and spirometry.
The survey used identical questionnaire in 1989 as
they used in 1975, and found that the prevalence of reported asthma or wheeze significantly
increased from 26.2% to 34.0% over the 14 year period.
Asthma increase in the USA
The US centre for Disease Control and Prevention noted an increase in the prevalence
of asthma in children in the US from 3.6% in 1980 to 5.8% in 2003.
Food Allergy Epidemic
Rising Prevalence of Peanut allergy in Children from 2 Sequential Cohorts in
Isle of Wight (5)
This is probably one of the most famous and frequently quoted studies on peanut
allergy internationally. Researchers looked at 2878 children born between 1994 and
1996, doing questionnaires, and 1246 had skin prick tests at age 3-4 yrs and those
with positive response to peanut had an oral peanut challenge. This was compared
with a similar cohort from the same area born in 1989. There was a 2-fold increase
in reported peanut allergy, and a significant 3-fold increase in peanut sensitization
from 1.1% in 1989 cohort up to 3.3% of the children 6 years later (the 1994-1996
Increasing prevalence of peanut allergy in Australia (6)
A recent study by Ray Mullins in Canberra, Australia examined the characteristics
of 778 patients with confirmed peanut allergy between 1995 and 2007, and found that
the incidence of peanut allergy in Canberra (Australian Capital Territory) more
than doubled in the children born in 2004 (1.15%) compared to those born in 1995
Evidence for an Anaphylaxis Epidemic (7)
On reviewing the medical literature, there was only rare and scattered reporting
of anaphylaxis, up until in the 1960s when the first small case series of individuals
with anaphylaxis to foods, drugs, and insect venoms was published. This was followed
- In the 1970s the first case series of idiopathic anaphylaxis
The first case series of exercise-induced anaphylaxis and latex-induced anaphylaxis
were reported in the 1980s
The first epidemiologic study looked at the incidence of anaphylaxis in the Minnesota,
USA noted an increase from 20 per 100,000 in 1993 to a high of 70 per 100, 000 in
Recent time trend studies in the UK showed that hospitalization for anaphylaxis
increased recently by 700%
Anaphylaxis fatalities and admissions in Australia (10)
Liew, Williamson and Tang looked at the causes, demographics and time trends of
anaphylaxis fatalities in Australia between January 1997 and December 2005, and
found that food-induced anaphylaxis deaths increased by about 300% , and drug-induced
deaths by about 150% over the eight year period. The authors found drugs were the
commonest cause of anaphylactic deaths about 60%, followed by insect stings (18%),
and foods (6%).
Trends in hospitalization for allergies in Australia (11)
Data on hospital admissions and deaths for anaphylaxis, angioedema (swelling of
soft tissues), and urticaria (hives) were examined for the periods 1993-1994 to
2004-2005 respectively. Over the 8-year period, the researchers found 106 deaths
from anaphylaxis and a continuous increase in the rate of hospital admissions for
angioedema (3% per year), urticaria (5.7% per year), most strikingly, anaphylaxis
(8.8% per year).
Allergic sensitization in infants with atopic eczema from different countries
2184 infants with atopic eczema were randomly screened in 12 countries, and it was
found that 55.5% of the infants were sensitized to at least one allergen. There
was a wide difference in sensitization to foods and aeroallergens globally. The
highest prevalence rate of sensitized infants was found in Australia 83%, the UK
79%, and Italy 76%. Belgium and Poland had the lowest sensitization rates.
The Latex Allergy Epidemic
Latex glove were first used by William Halstead back in 1890. Since then their use
has progressively increased in medicine, until roughly 100 years later when the
latex allergy epidemic occurred. The latex allergy epidemic is probably the best
example of an allergic disease that increased in prevalence to "epidemic" proportions
in the last two centuries and due to careful planning the "epidemic" has been contained,
and the prevalence has fallen over the last 8 years. Latex is a common component
of many medical supplies including disposable gloves, intravenous tubing, syringes,
stethoscopes, catheters, and bandages. It was therefore not surprising that the
latex epidemic was confined to health care workers and patients that have had several
previous surgical operations.
The sudden rise in the use of latex gloves to prevent the spread of AIDS and Hepatitis
B in the 1980s is blamed for the latex allergy epidemic which peaked between 1996
and 2000. To keep up with the demands of increased glove production the manufacturing
time had to be decreased by reducing the number of washing and purifying steps.
This resulted in increased amounts of sensitizing protein that the gloves could
transmit. Another very interesting finding in this epidemic was the fact that the
prevalence was much higher in genetically susceptible individuals, atopics. So this
highlights the belief that increased exposure to a highly allergenic substance in
a genetically susceptible population could contribute to the allergy epidemic.
In 1994 Blanco coined the term ‘latex-fruit syndrome”, due to the fact
that 52% of their patients with latex allergy were sensitized to fruits: 36% were
sensitized to avocados, 36 to chestnuts, 28% to bananas, and 20% to kiwis. This
example of adult-onset fruit allergy is very much like the "birch-fruit syndrome"
which is responsible for the "epidemic" of fruit allergy that is being experienced
in New Zealand adults at the moment.
Causes of the Allergy Epidemic
The causes of the allergy epidemic are complex interplay between genetics and environmental
changes. The time frame for the increased prevalence of allergies is too short to
explain a genetic change in the population. Therefore most of the current epidemiological
research has focused on identifying possible environmental factors that are associated
with the increased prevalence of allergies. Some of the proposed reasons due to
environmental changes over the last 30 years, that could be contributing to the
allergy epidemic include:
Parental cigarette smoking has been strongly correlated with increased prevalence
of allergies in offspring
Formula feeds instead of exclusively breast-feeding for the first 4-6 months, which
is known to decrease the risk of allergies. Breastfeeding promotes colonization
of the infant’s gut with bifidobacteria and lactobacilli, which in necessary
for the development of normal oral tolerance to foods
Dietary factors are being explored, since the modern dist is very different from
the diet 20 years ago. Researchers are looking at vitamins, especially Vitamin D,
Folic acid and the effects of sunlight in terms of their effects on allergies
Use of antacids may prevent the destruction of potential allergens, and infants
are increasingly being given potent acid suppressing drugs for reflux disease
Hygiene Hypothesis – is the most popular theory that supports the "allergy epidemic".
Over the last 20 years there have been striking improvements in medical science
and hygiene, and this has led to increased life expectancy due to decreased infections
from harmful microorganisms. This reduced microbial load early in life could have
a down side; it could be one of the causes of the increased incidence of allergic
diseases, seen over the last 2 centuries. A review of the medical literature between
1966 until 2004 identified more than 20 prospective studies which showed an inverse
relationship between allergies and microbial infection or endotoxins related to
microbes. Some well designed studies supporting the hygiene hypothesis include:
The risk of allergies is higher in children growing up in smaller families, and
families of higher socioeconomic status, as seen in developed countries. One study
showed lower incidence in younger siblings, when there is 3 or more older siblings,
and another showed decreased incidence in children who attend day care but only
if they are without siblings
- Low incidence of allergies in children growing up on farms
One study showing a positive association between infections in early life and a
reduced risk of atopic eczema
Several studies showing antibiotic use in early life and even in the antenatal period
associated with increased risk of atopic eczema
A study done in Italy, and published in the BMJ in 1997, showed that young men with
antibodies to Hepatitis A virus had a lower prevalence of allergic diseases. Hepatitis
A, in this case could be considered a marker for poor hygiene
A few small randomized controlled trials have shown that probiotics could reduce
severity and prevalence of some allergies.
To put it briefly, we can say that the allergy epidemic which is occurring in developed
countries, with a higher living standards, is probably a result of modern life style,
where there is an almost obsession with cleanliness. Infants are not getting exposed
to bugs and germs as they use to, there fewer childhood infections, families are
smaller, along with more frequent use of antibiotics in infancy are all contributing
to the "hygiene hypothesis".
Increased prevalence of peanut allergies possibly related to advice given by health
care professional (13)
One study in the UK showed that when peanut was introduced to children at about
12.6 months for a cohort born in 1989, the peanut allergy rate was 0.5%, and when
it was introduced around 36 months for a cohort born between 1999 and 2000, the
peanut allergy rate went up to 1.8%. Also Du Toit and others have found that the
prevalence of peanut allergy among Jewish schoolchildren in the UK was 1.85% compared
to 0.17% in schoolchildren living in Israel. This almost 10-fold higher rate is
probably due to the much lower consumption rate of peanut in UK children. Peanut
is introduced earlier and is eaten more frequently and in larger quantities in Israel.
The median monthly consumption in Isreali infants from 8 – 14 months was 7.1 g compared
to 0 g in their UK counterpart. Another study in the UK showed that high levels
of environmental exposure to peanut in infancy, when associated with no ingestion
of peanuts appear to promote peanut sensitization.
The low peanut consumption in infancy is probably related to the 1998 UK Department
of Health’s Committee on the Toxicology of Chemicals in food advice on the consumption
of peanut and peanut products in preventing peanut allergy. The Committee advised
that peanut should be avoided by pregnant breast-feeding atopic women and those
children with a parent or sibling who is atopic should avoid peanuts up until three
years. Incidentally, this advice was adopted in New Zealand and other developed
countries that are experiencing this peanut allergy epidemic.
Looking into the future: How can we reverse or halt the epidemic?
The good news is that, it has been shown that these diseases can be controlled effectively
through increased awareness, National and International Guidelines (protocols),
which leads to better management The health proffessionals’response to the asthma
and the latex epidemic has led to stabilization or even reduction in symptoms and
new cases (in the case of latex epidemic). Through National Guidelines and policies
we have seen that the epidemic can be managed until a “cure” is found.
Also we might be learning from the peanut allergy epidemic, that until the studies
on allergy prevention are completed, we need to be careful with the advice we give
to our patients.
Hospital policy and Guidelines used to effectively combat the latex epidemic
Since 1999 the US FDA has regulated the need for manufacturers to apply warning
labels on medical devices containing natural rubber latex. Also medical device companies
have developed many latex-free alternatives.
Internationally, over recent years hospitals have developed policies and guidelines
recommending the use of non-powdered, reduced-latex, or latex-free (non-latex),
"hypoallergenic" gloves. Follow-up studies have shown reduced latex sensitization
and asthma in HCW, and even shown a reduction in latex-specific IgE antibodies after
latex use has been substantially reduced in the health care workplace.
In the UK prior to 2002, several health care workers have been compensated by their
employers for developing latex allergy. A trainee nurse was awarded more than £300,000
compensation in an out of court settlement with Scarborough General Hospital NHS
Trust after developing allergy to latex gloves. In another case, a nurse was awarded
₤354,000 compensation after "she was forced to abandon her nursing career due to
an allergy to latex." Probably because of these cases, in the UK, natural latex
rubber is now classified as a substance hazardous to health, and as such it falls
under the Control of Substances hazardous to Health regulations 2002. (COSHH). Under
COSHH, employers must access all the circumstances in which employees may be exposed
to substances hazardous to health.
In Belgium the use of powdered latex gloves fell from 80.9% in 1989 to 17.9% in
2004, and this is paralleled with the national compensation-based data confirmation
of a persistent decline in the incidence of latex-induced occupational asthma has
occurred since late 1990s.
We can learn from this epidemic that atopic adults are likely to become allergic
to an allergen if the allergen exposure is high enough. We might not necessarily
be able to extrapolate this to prevention of food allergy in infants, but in genetically
susceptible adults, we can prevent certain occupational allergies, with the possible
Phase 3 ISSAC study showed a decrease in asthma symptoms due to better control
As discussed earlier, the Phase 3 ISAAC study has demonstrated a reduction in asthma
symptoms in 6-7 year-old and 13-14 year-olds in New Zealand.
However, one should not get complacent, because this same study has showed that
"asthma reported ever" has increased in both age groups, suggesting that the improvement
of asthma symptoms is due to better management of the disease.
In conclusion, allergies, including, asthma, eczema, hay fever, food allergy, and
anaphylaxis have increased in New Zealand and other developed countries by epidemic
proportions over the last 25 years. The “Hygiene hypothesis” or diminished
microbial stimulation of the immune system of infants has been cited as one of the
main cause for this “epidemic”, and there are some good studies to support
this theory. However, the exact cause is far from being certain, at the present
We know from the response to the latex and asthma epidemic that we can reduce symptoms
and increase quality of lives in allergy suffers. However, controlling the symptoms
of the diseases in the “allergy epidemic” is only apart of the solution.
We also need to reverse the increasing allergic sensitization in developed countries.
However, we can only do this when we have figured out the cause(s) for this increase,
and this will only be done through more very good international studies like GALEN
and ISAAC. New Zealand needs to follow the example set by the GA²LEN study in Europe,
and invest more into funding of research into allergies.
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