Allergic diseases have been increasing in prevalence worldwide over the last few decades, partly as the result of the impact of climate change.1 Climate change leads to increases in extreme weather events, such as flooding, bushfires and thunderstorms.2 Changes in temperature, rainfall, and other variables of climate change have been shown to indirectly affect allergies and asthma by influencing pollen and mould formation.3 Changes in vegetation, increased spore concentrations and prolonged pollen seasons are all linked to climate change and the effect on human health is well documented, specifically with regard to allergies.4 The impacts of climate change on allergens and allergic diseases are important and potentially serious in Australia. Australia is highly vulnerable to such impacts because of its high prevalence of allergic disease and increasing allergic sensitisation to environmental allergens.5 An analysis of available pollen data indicates that the composition and abundance of airborne pollen in urban Australian areas are strongly influenced by climate.6 Evidence has shown further effects on mould formation and growth in indoor environments due to increases in humidity and water damage risk.5 Beyond respiratory allergens, climate change may also affect food allergens, stinging insect allergens and contact allergens in Australia.5
Aeroallergens refers to any airborne substance, such as pollen or mould spores, which triggers an allergic reaction. These aeroallergens in combination with exposure to air pollutants act synergistically to intensify the allergic response.7 (See figure 1)
Figure 1: The mechanism by which aeroallergens increase risk of allergic respiratory diseases
Figure 2: The intersection of the environment, climate change and allergic disease
Air pollution and climate change have resulted in faster growth of allergenic plants, increasing the air allergen load for patients with inhalant allergy.8 Air pollution not only affects plant growth, pollen and flower production, but also induces direct health effects by increasing the amount of allergenic protein exposure.9 Higher atmospheric levels of carbon dioxide leads to enhanced photosynthesis and greater reproductive effects exhibited by plants, producing more pollen as a response.10 Other air pollutants such as nitrogen dioxide can directly influence the allergenicity of pollens, while simultaneously promoting adaptive immune responses to non-toxic agents.1 Vehicular-exhaust pollution has also been reported to increase pollen allergenicity.11
Weather events related to climate change including drought or extreme rainfall, wind gusts, thunderstorms and any kind of extreme meteorological event can influence pollen concentrations.1 Higher rainfall prior to pollen liberation can lead to increased plant and flower production, thereby increasing available pollen for release.12 Lightning storms or wet conditions rupture pollen grains releasing the allergenic proteins that cause asthma exacerbations in patients with pollinosis (thunderstorm-asthma).13 These smaller size pollen fragments permit their entry deep into the lungs, intensifying the allergic response. Increases in mould caused by heavier rainfall and higher temperatures can lead to respiratory and asthma-related conditions. Provoking an immune response, these moulds can produce and release millions of airborne spores that can be easily inhaled, causing hay fever and asthma associated symptoms.14
Bushfires and deforestation
Bushfires are becoming increasingly frequent in Australia and have been linked to climate change. The fine particle matter in bushfire smoke exacerbates asthma attacks, where it has been shown that subjects who have been exposed to bushfire smoke have significantly higher levels of inflammatory markers, indicative of airway inflammation.15 Smoke emissions from bushfires can travel hundreds of kilometers, exposing people to a complex mixture of fine particles. Furthermore, bushfires and deforestation can lead to desertification. In dry conditions, more pollen, dusts and smoke can irritate respiratory epithelium, exacerbating chronic respiratory illnesses, allergies and asthma.16
The risk factors for allergies and asthma include both genetic and external triggers. Those who have a family history of atopy are more likely to be susceptible to environmental insults.17 City dwellers have a greater risk of allergic respiratory diseases because of the synergistic exposure to air pollutants, high temperatures and allergens. Migration from rural regions to urban centers is accompanied by an increased rate of asthma.18 Therefore, urban populations will be disproportionately affected by further increases in air temperature, as excess heat can directly impact respiratory airways by exacerbating inflammation and bronchoconstriction, leading to shortness of breath.19
Children have higher asthma and allergy prevalence than adults and are more sensitive to environmental exposure. During the critical phase of lung development, exposure of the airway epithelium to environmental insults may lead to persistent and life-long changes to lung structure and function.20 A birth cohort study reported that exposure to allergens in the first 3 years of life impaired lung function in children and influenced the development of adult asthma.21 Prenatal and perinatal exposure to air pollutants has also been linked to increased respiratory symptoms and asthma risk in childhood.22
- Education around symptom surveillance, trigger identification and exposure reduction.
- Implementing extra precaution strategies when allergy levels are high; monitoring pollen counts, staying indoors where possible, wearing a pollen mask and taking preventions to reduce hypersensitivity.
- Promoting the utilisation of available technology for monitoring airborne pollen levels such as AirRater – tracks exposure of temperature, air particles and aeroallergens.30
Such technologies improve understanding of how environmental conditions affect your health, providing you with a means to better manage disease.
- Air purifiers can effectively reduce particle matter and dust mite concentration indoors, thereby improving clinical manifestations of patients with allergic rhinitis.31
- Routinely clean air conditioning systems to reduce build-up and expelling of mould spores.32 Using pure lemon essential oil in the cleaning water with a microfibre cloth can reduce mould in the indoor unit. It’s best to have your system cleaned professionally at least once a year.
- Dehumidifiers reduce the likelihood of mould growth indoors during humid seasons or climates. Humidity control also reduces the growth of other indoor allergens such as dust mites.32
In a changing world, complementary healthcare professionals have a significant role to play in patient education and allergy management.
Various clinical interventions can be considered to minimise climate change-related risk in allergenic respiratory diseases. Identifying and addressing individuals with risk factors combined with tailored prescriptions may help patients better adapt to changing exposures.
Article courtesy: BioMedica Neutraceuticals
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- Climate Central. https://www.climatecentral.org/gallery/graphics/top-10-warmestyears-on-record (Top 10 Warmest Years on Record) (2020).
- Ziska, L. In Impacts of Climate Change on Allergens and Allergic Diseases (ed P. Beggs) 92–112 (Cambridge University Press., 2016).
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