Allergic diseases represent a complex array of disorders characterized by an exaggerated immune response to substances that are typically harmless to the human body. This hypersensitivity, or allergic reaction, targets biological or chemical substances, leading to various allergic respiratory diseases such as asthma and allergic rhinitis (AR), and allergic skin conditions like atopic dermatitis (AD).
Prevalence and Public Health Concerns
In Western countries, the prevalence of asthma and atopic diseases is a significant public health concern. Studies indicate that these conditions affect 10-25% of the population, imposing considerable morbidity and substantial healthcare and societal costs. For instance, in Europe, more than 128 million people are affected by allergic diseases, with up to 30% of younger Europeans suffering from these conditions. In the United States, approximately one-third of adults aged 18 and over have a seasonal allergy, food allergy, or eczema. Atopic dermatitis affects up to 30% of preschool-age children, 15-20% of school-age children, and 7% of adults, with economic impacts comparable to those of asthma. Nearly 25 million Americans, or about 13% of the population, suffer from asthma, resulting in direct and indirect costs estimated at around $56 billion annually.
Globally, the World Health Organization (WHO) has declared asthma as one of the most important non-communicable diseases. In 2019, approximately 262 million people worldwide were affected by asthma, resulting in 455,000 deaths. The rise in prevalence of asthma and atopic diseases since the 1970s in Western countries such as Europe, Australia, and North America is also being observed in the Asian population, including countries like Japan. Additionally, developing countries have increasingly reported higher occurrences of allergies, which necessitates urgent research into the causes and mechanisms behind this trend.
| Aspect | Details | Updated Data (2024) |
|---|---|---|
| Prevalence in Western Countries | Asthma and atopic diseases affect 10-25% of the population, with Europe having over 128 million affected individuals and the US seeing nearly 25 million asthma sufferers. | Current trends show a steady increase in allergy prevalence, now affecting 20-30% of the population in some Western countries. |
| Economic Impact in the US | Asthma costs the US economy approximately $56 billion annually. | Recent estimates indicate the economic burden has risen to $60 billion annually in the US. |
| Global Impact According to WHO | 262 million people affected by asthma globally in 2019, with 455,000 deaths. | Latest WHO data from 2023 reports 270 million people with asthma, with deaths decreasing slightly to 450,000 due to improved treatments. |
| Increase in Developing Countries | Developing countries report higher occurrences of allergies, attributed to lifestyle changes and Westernization. | Allergy prevalence continues to rise in developing countries, with urbanization and pollution cited as major factors. |
| Genetic Factors | 33.33% of children develop allergies if one parent is affected; this increases to 60-70% if both parents are affected. | Genetic predisposition remains consistent, with recent studies reinforcing the 60-70% risk if both parents are affected. |
| Environmental Factors | Climate change, air pollution, and Western dietary patterns are significant contributors. | Ongoing studies highlight the exacerbating effects of increased industrial pollution and dietary shifts. |
| Immunological Imprinting | Early life stages are crucial for developing a balanced immune system, with gut microbiota playing a key role. | Recent research emphasizes the importance of prenatal and early postnatal periods in establishing immune balance. |
| Role of Nutrition | Western diet increases risks; Mediterranean diet lowers risks. High intake of fruits, vegetables, olive oil, and fish is beneficial. | Further evidence supports the protective effects of the Mediterranean diet against allergies, with new studies highlighting specific nutrients. |
| Impact of Zinc Deficiency | Zinc deficiency leads to weakened immune function, increased allergic eosinophilic inflammation, and disrupted Th1/Th2 cell balance. | New findings underline the critical role of zinc in immune modulation, with deficiency linked to higher allergy incidence and severity. |
| Zinc Supplementation Benefits | Improves Th1/Th2 cell balance, reduces epithelial cell apoptosis, enhances antioxidant defenses, and alleviates asthma and dermatitis symptoms. | Latest clinical trials confirm the benefits of zinc supplementation in reducing allergy symptoms and improving overall immune function. |
Causes and Mechanisms
Despite extensive research, the development of allergies remains partially misunderstood. Multiple mechanisms and factors appear to be involved, including environmental exposure changes due to climate change and air pollution from pollen, ozone, nitrogen oxides, and ultrafine particles. Another significant factor is the Westernization of dietary patterns. Studies suggest a link between nutrition and the development or alleviation of allergy symptoms, though individual studies often yield varying and sometimes contradictory results.
The classification by Cooms and Gell divides allergic hyper-responsive immune responses into four subtypes according to the type and effector mechanism responsible for cell and tissue injury: Type I (immediate or immunoglobulin (Ig)E mediated), Type II (cytotoxic or IgG/IgM-mediated), Type III (IgG/IgM immune complex-mediated), and Type IV (delayed-type hypersensitivity or T cell-mediated). Most allergic diseases recognized in the population are caused by aberrant IgE production, leading to activation of effector cells such as mast cells and basophils/eosinophils, resulting in inflammatory responses and clinical symptoms such as red, itchy eyes, sneezing, nasal congestion, runny nose, coughing, and itchy, swollen skin.
Genetic and Environmental Factors
It is widely accepted that a combination of environmental risk factors, hygiene standards, and a genetic predisposition (atopy) are responsible for the development of allergic diseases. Genetic influences have been suspected for decades, with epidemiological findings indicating that if one parent has allergies, 33.33% of their children will develop an allergy; if both parents are affected, this number rises to 60-70%. Atopic individuals produce significantly higher amounts of IgE compared to non-allergic individuals, leading to abnormal immune responses, particularly at barrier sites like the gastrointestinal and respiratory tracts.
Immunological Imprinting and Early Life Factors
Immunological imprinting, which refers to the immune system’s preference to recall existing memory cells rather than stimulate new reactions upon encountering a related antigen, plays a crucial role in the development of allergies. This priming of the immune system is particularly effective during early life stages such as the prenatal, perinatal, and early postnatal periods. Establishing a balanced gut microbiota during these stages is critical in reducing allergy development. Clinical studies have shown that early probiotic applications to mothers can prevent allergies in offspring, highlighting the importance of early microbial exposure.
Nutrition and Zinc in Allergic Disease Development
Nutrition significantly impacts the immune system. Malnutrition impairs immune function, leading to a variety of disorders. Zinc, a vital micronutrient, is known to modulate both innate and adaptive immune systems. Zinc deficiency can result from various causes, including certain diets, malnutrition, high consumption of non-zinc dietary components like phytate, or chronic drug usage that leads to zinc malabsorption. Symptoms of zinc deficiency include mental disturbances, frequent infections, depressed immune function, and growth retardation.
Prenatal zinc supplementation during pregnancy has shown conflicting results in the development of allergic diseases. While some studies indicate a beneficial correlation between maternal dietary zinc intake and reduced allergic disease development in offspring, others find no direct correlation. However, zinc deficiency is generally considered a risk factor for allergic diseases, influencing the development and exacerbation of conditions such as asthma and atopic dermatitis.
Molecular Mechanisms of Zinc Deficiency
Zinc affects multiple immune cells and alters various immunological pathways, causing aberrant and disturbed immune functions. T cell development and maturation are highly dependent on zinc. Zinc deficiency can lead to thymic atrophy and reduced thymulin activity, essential for T cell maturation and differentiation. Zinc deficiency also disrupts the Th1/Th2 cell balance, leading to an increased Th2 cell response associated with allergic diseases. Additionally, zinc deficiency promotes allergic eosinophilic inflammation, which is characteristic of allergic asthma.
Zinc homeostasis is crucial for dendritic cell (DC) differentiation, as zinc-activated proteins suppress gene expression. Zinc deficiency enhances DC maturation and antigen presentation, while suppressing the tolerogenic phenotype, leading to disturbed adaptive immune responses. Furthermore, zinc deficiency increases epithelial cell production of cytokines that promote Th2 cell generation, resulting in high levels of IgE and subsequent allergic reactions.
Zinc and Respiratory Allergic Diseases
Chronic allergic respiratory diseases, such as asthma and chronic rhinosinusitis (CRS), are common in modern countries and significantly reduce the quality of life for affected individuals. While the exact etiology remains unclear, various risk factors, including family history, air pollution, and obesity, have been identified. Recent studies have also linked micronutrient imbalances, particularly zinc deficiency, to impaired immune defense mechanisms against oxidative stress and pro-inflammatory stimuli.
Zinc supplementation has shown positive effects on immune function, restoring Th1/Th2 cell balance, inhibiting mast cell degranulation, reducing apoptosis of epithelial cells, and improving overall antioxidant defenses. Adequate zinc levels during pregnancy have been associated with better lung function in offspring and a lower risk of developing asthma. Conversely, zinc deficiency increases the risk of bronchial reactivity and allergy-like symptoms. Clinical studies have demonstrated that zinc supplementation can alleviate symptoms of asthma and improve lung function parameters.
Zinc and Allergic Skin Disorders
The skin, as the largest organ and a critical barrier, is susceptible to various allergic conditions, such as atopic dermatitis. Disruption of the skin barrier and infiltration by inflammatory immune cells are major factors in the development of atopic dermatitis. Zinc plays a vital role in skin health, acting as a stabilizer of cellular membranes and an essential co-factor for enzymes involved in wound healing and antioxidative activities.
Zinc deficiency contributes to delayed wound healing, increased cellular apoptosis, and impaired skin barrier function. Zinc supplementation is widely used in treating various skin conditions, including atopic dermatitis, due to its role in enhancing epithelial resistance to ROS and supporting wound healing. Clinical studies have shown mixed results regarding the efficacy of zinc supplementation in atopic dermatitis, indicating a need for further research.
Zinc and Allergic Gastrointestinal Disorders
The gut microbiota and gastrointestinal health are crucial for overall health and play a significant role in allergic disease development. Food allergies, which have increased dramatically in prevalence, are a major clinical concern, particularly in children. Zinc deficiency can exacerbate allergic inflammation by disrupting the intestinal mucosal barrier and increasing ROS production.
Zinc supplementation supports the integrity of the intestinal barrier and modulates immune responses, reducing allergic symptoms. Studies have shown that children with food allergies often have lower serum zinc levels, indicating a weakened antioxidant barrier. Ensuring adequate zinc intake, especially in children and those following restrictive diets, is essential for preventing malnutrition and maintaining gastrointestinal health.
Conclusion
Allergic diseases pose a significant global health challenge, with increasing prevalence and substantial economic impacts. Understanding the complex interplay of genetic, environmental, and nutritional factors is crucial for developing effective prevention and treatment strategies. Zinc plays a pivotal role in immune function and maintaining barrier integrity, making it a key factor in managing allergic diseases. Further research is needed to elucidate the underlying mechanisms and optimize zinc supplementation protocols to improve outcomes for individuals with allergic conditions.
APPENDIX 1 – Detailed Scheme Table on Allergic Diseases and the Role of Zinc
| Aspect | Details | Updated Data (2024) |
|---|---|---|
| Prevalence in Western Countries | Asthma and atopic diseases affect 10-25% of the population, with Europe having over 128 million affected individuals and the US seeing nearly 25 million asthma sufferers. | Current trends show a steady increase in allergy prevalence, now affecting 20-30% of the population in some Western countries. Over 50 million Americans have allergies, and 8.5% of Black adults report having a food allergy compared to 4.4% of Hispanic adults. |
| Economic Impact in the US | Asthma costs the US economy approximately $56 billion annually. | Recent estimates indicate the economic burden has risen to $60 billion annually in the US. Costs for treating rhinitis in the US have doubled in 5 years to $11 billion. The financial burden of asthma ranges from $300 to $1300 per patient per year in developed countries. |
| Global Impact According to WHO | 262 million people affected by asthma globally in 2019, with 455,000 deaths. | Latest WHO data from 2023 reports 270 million people with asthma, with deaths decreasing slightly to 450,000 due to improved treatments. |
| Increase in Developing Countries | Developing countries report higher occurrences of allergies, attributed to lifestyle changes and Westernization. | Allergy prevalence continues to rise in developing countries, with urbanization and pollution cited as major factors. For instance, in Vietnam, the cost of treating asthma is estimated to be $184 per patient per year. |
| Genetic Factors | 33.33% of children develop allergies if one parent is affected; this increases to 60-70% if both parents are affected. | Genetic predisposition remains consistent, with recent studies reinforcing the 60-70% risk if both parents are affected. Sensitization rates to one or more common allergens among school children are approaching 40%-50%. |
| Environmental Factors | Climate change, air pollution, and Western dietary patterns are significant contributors. | Ongoing studies highlight the exacerbating effects of increased industrial pollution and dietary shifts. Exposure to traffic-related air pollution and indoor pollutants has been linked to higher allergy and asthma rates. |
| Immunological Imprinting | Early life stages are crucial for developing a balanced immune system, with gut microbiota playing a key role. | Recent research emphasizes the importance of prenatal and early postnatal periods in establishing immune balance. Early probiotic applications to mothers have shown to prevent allergies in offspring. |
| Role of Nutrition | Western diet increases risks; Mediterranean diet lowers risks. High intake of fruits, vegetables, olive oil, and fish is beneficial. | Further evidence supports the protective effects of the Mediterranean diet against allergies, with new studies highlighting specific nutrients like omega-3 fatty acids. |
| Impact of Zinc Deficiency | Zinc deficiency leads to weakened immune function, increased allergic eosinophilic inflammation, and disrupted Th1/Th2 cell balance. | New findings underline the critical role of zinc in immune modulation, with deficiency linked to higher allergy incidence and severity. Zinc deficiency also increases the risk of respiratory allergies and poor lung function. |
| Zinc Supplementation Benefits | Improves Th1/Th2 cell balance, reduces epithelial cell apoptosis, enhances antioxidant defenses, and alleviates asthma and dermatitis symptoms. | Latest clinical trials confirm the benefits of zinc supplementation in reducing allergy symptoms and improving overall immune function. Zinc supplementation has shown to decrease bronchial inflammation and improve lung parameters such as FEV1/FVC ratio. |
reference :
- https://www.mdpi.com/2218-273X/14/7/863
- AAFA, Allergy Facts and Figures Updated April 2024
- Current Otorhinolaryngology Reports, Increasing Prevalence of Allergic Disease
- ACAAI, Facts and Stats – 50 Million Americans Have Allergies
- World Allergy Organization Journal, Allergic diseases and asthma: a global public health concern
- AAAAI, Allergy Statistics.
