Over the last few decades there has been a dramatic rise in the rate and severity of allergies, particularly in children. This increased prevalence of allergy is heavily associated with an increasingly wealthy, modern Western society. Allergies are not overly prevalent in under-developed countries, suggesting that the rise of allergy in industrialised countries is due to factors specific to Western society, bringing the question – are allergies a 'First World Problem'?
What is causing this rise in allergy?
There is some support for the rise of allergies being partially due to increased awareness and diagnosis, however the majority of experts agree that overall the increase is largely due to a higher percentage of people developing allergies. However, the precise cause of this increase is still under debate, with a number or theories suggested.
Hygiene Hypothesis
In 1989 the term 'Hygiene Hypothesis' was coined to address the theory that an increasingly sterile environment in modern society has caused our immune system to initiate and react to various substances (allergens) as if they were harmful. Factors such as decreased family sizes and increased cleanliness and hygiene standards (such as the increased use of liquid soap, most of which boast 'anti-bacterial' properties) have dramatically reduced the exposure to dangerous disease-causing pathogens. However as an unattended consequence it may have also contributed to the significant increase in allergic sensitivities.
Old Friends Mechanism
However, although there is some evidence to support the 'Hygiene Hypothesis', critics suggest that the rise in allergy isn't due to a more sanitised environment, but rather a decreased exposure to a diverse range of microbes. In 2003 this refinement was termed the 'Old Friend's Mechanism' and suggests that it is the microbes that co-evolved alongside our immune systems that are essential for building a diverse gut microbiome and sustaining a well-regulated immune system.
This hypothesis suggests that lifestyle changes have decreased our exposure to these generally harmless microbes and have caused our immune systems to raise an immune response to harmless allergens. For example, children in today's society are more likely to be found inside in front of a screen rather than playing outside in the dirt where they would be exposed to numerous microbes. Studies have demonstrated that children who are raised on a farm have a low prevalence of allergic sensitisation. Likewise, children who attend day care, have older siblings or have a pet are also less likely to develop allergies. What all these factors have in common is an increased exposure to a diverse range of microbes, suggesting that a decreased exposure to such microbes may indeed contribute to the significant rise in allergic sensitivities.
Antibiotics
Another arm of the 'Old Friends Mechanism' believed to contribute to the rise of allergy incidence is the increased use of antibiotics. Today, antibiotics are prescribed frequently and quickly, often at the first sign of illness. It is well-documented that antibiotic use causes long term alterations to our gut microbiota (the microbes that live in our gut), and considerable evidence indicates that this may contribute to the development of certain allergies. Dr Gary Huffnagle, University of Michigan, provided the first experimental evidence for the role of antibiotics and microbes in the development of allergic airway disease. The study showed that an alteration of the gut microbiota due to a course of antibiotics caused an increased hypersensitivity and reactivity in the lungs of mice in response to harmless yeast spores.
In particular, antibiotic use during the early years of life is shown to significantly impact the risk of childhood atopy (a genetic tendency to develop allergic diseases), in particular sensitivity to food allergens. The immune system continues to evolve throughout the early years of life and having a diverse gut microbiome is highly beneficial to health. Disruptions to the gut microbiota (due to antibiotic use and other factors) are increasingly shown to be associated with a variety of diseases, including allergy.
Vitamin D deficiency
In addition to the role of microbes in allergy, vitamin D deficiency has been linked to the rise in allergies, with a noticeable increase in allergies in climates where vitamin D levels tend to be lower, such as those further away from the equator. Vitamin D deficiency has increased over recent years and has been contributed to inadequate exposure to sunlight due to people spending more time indoors, which could be contributed to a modern Western lifestyle. Australian researchers have demonstrated that children with vitamin D deficiency are three times more likely to develop food allergies. Currently there is conflicting evidence regarding the role of vitamin D in allergic diseases with further research required to determine how much of a role vitamin D deficiency has on the development of allergy.
A modern, Western society is often associated with more wealth, increased hygiene and cleanliness, increased access to and use of medications including antibiotics, and more time spent indoors for both work and leisure. Various studies have shown that these lifestyle factors may contribute to the development of allergic sensitivity due to a decreased exposure to a diverse range of microbes, however, further research is required to determine how much of a role this has in why the immune system reacts to harmless environmental factors. For now, it certainly appears that the so called 'First World' lifestyle has contributed to the rise in allergy.
What is causing this rise in allergy?
There is some support for the rise of allergies being partially due to increased awareness and diagnosis, however the majority of experts agree that overall the increase is largely due to a higher percentage of people developing allergies. However, the precise cause of this increase is still under debate, with a number or theories suggested.
Hygiene Hypothesis
In 1989 the term 'Hygiene Hypothesis' was coined to address the theory that an increasingly sterile environment in modern society has caused our immune system to initiate and react to various substances (allergens) as if they were harmful. Factors such as decreased family sizes and increased cleanliness and hygiene standards (such as the increased use of liquid soap, most of which boast 'anti-bacterial' properties) have dramatically reduced the exposure to dangerous disease-causing pathogens. However as an unattended consequence it may have also contributed to the significant increase in allergic sensitivities.
Old Friends Mechanism
However, although there is some evidence to support the 'Hygiene Hypothesis', critics suggest that the rise in allergy isn't due to a more sanitised environment, but rather a decreased exposure to a diverse range of microbes. In 2003 this refinement was termed the 'Old Friend's Mechanism' and suggests that it is the microbes that co-evolved alongside our immune systems that are essential for building a diverse gut microbiome and sustaining a well-regulated immune system.
This hypothesis suggests that lifestyle changes have decreased our exposure to these generally harmless microbes and have caused our immune systems to raise an immune response to harmless allergens. For example, children in today's society are more likely to be found inside in front of a screen rather than playing outside in the dirt where they would be exposed to numerous microbes. Studies have demonstrated that children who are raised on a farm have a low prevalence of allergic sensitisation. Likewise, children who attend day care, have older siblings or have a pet are also less likely to develop allergies. What all these factors have in common is an increased exposure to a diverse range of microbes, suggesting that a decreased exposure to such microbes may indeed contribute to the significant rise in allergic sensitivities.
Antibiotics
Another arm of the 'Old Friends Mechanism' believed to contribute to the rise of allergy incidence is the increased use of antibiotics. Today, antibiotics are prescribed frequently and quickly, often at the first sign of illness. It is well-documented that antibiotic use causes long term alterations to our gut microbiota (the microbes that live in our gut), and considerable evidence indicates that this may contribute to the development of certain allergies. Dr Gary Huffnagle, University of Michigan, provided the first experimental evidence for the role of antibiotics and microbes in the development of allergic airway disease. The study showed that an alteration of the gut microbiota due to a course of antibiotics caused an increased hypersensitivity and reactivity in the lungs of mice in response to harmless yeast spores.
In particular, antibiotic use during the early years of life is shown to significantly impact the risk of childhood atopy (a genetic tendency to develop allergic diseases), in particular sensitivity to food allergens. The immune system continues to evolve throughout the early years of life and having a diverse gut microbiome is highly beneficial to health. Disruptions to the gut microbiota (due to antibiotic use and other factors) are increasingly shown to be associated with a variety of diseases, including allergy.
Vitamin D deficiency
In addition to the role of microbes in allergy, vitamin D deficiency has been linked to the rise in allergies, with a noticeable increase in allergies in climates where vitamin D levels tend to be lower, such as those further away from the equator. Vitamin D deficiency has increased over recent years and has been contributed to inadequate exposure to sunlight due to people spending more time indoors, which could be contributed to a modern Western lifestyle. Australian researchers have demonstrated that children with vitamin D deficiency are three times more likely to develop food allergies. Currently there is conflicting evidence regarding the role of vitamin D in allergic diseases with further research required to determine how much of a role vitamin D deficiency has on the development of allergy.
A modern, Western society is often associated with more wealth, increased hygiene and cleanliness, increased access to and use of medications including antibiotics, and more time spent indoors for both work and leisure. Various studies have shown that these lifestyle factors may contribute to the development of allergic sensitivity due to a decreased exposure to a diverse range of microbes, however, further research is required to determine how much of a role this has in why the immune system reacts to harmless environmental factors. For now, it certainly appears that the so called 'First World' lifestyle has contributed to the rise in allergy.
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