The nose as the airway gatekeeper, is responsible for filtering, humidifying and warming air (10,000 litres daily). Rhinitis is inflammation of the nasal lining with clinically symptoms includes nasal running, sneezing, itching, rhinorrhoea and obstruction. Allergy (via IgE-mediated mast cell degranulation) is common reason of rhinitis, which is common allergic disorders. Allergen avoidance is remarkably effective in AR patients and immunotherapy is important absolute treatment of AR, but there are some challenges to this treatment (7-9). AR is common disease in children and affects up to 50% of the pediatric population worldwide. The AR medications (seasonal and perennial) have an impact on the quality of life. Available treatments of AR include anti-histamines, intranasal corticosteroids, immunotherapy, and anti-leukotrienes. The anti-histamine drugs are first-line therapy for AR, and first-generation anti-histamine drugs are associated with adverse effects (such as sedation) that are caused by the lack of H1 receptor selectivity and the drug penetration into the central nervous system. Therefore, the second-generation anti-histamine drugs were developed with less frequent adverse effects. The intranasal corticosteroid drugs can be absorbed through airway epithelium and may have effect on hypothalamic-pituitary-adrenal axis suppression. Montelukast as an antagonist of the leukotriene receptor, which binds to the cysteinyl leukotriene receptor 1 with high affinity. Environmental factors such as weather conditions may have effect on the LTs (10-12). AR group that were challenged with cold air conditions had increased histamine level compared to the AR group in normal air conditions and it was showed that decreased temperature and cold weather can stimulate histamine releasing and clinical output of allergic reaction in the influenced tissue, especially mucosal and sub-mucosal tissue of airways. Therefore, for control of these problems, anti- histamine drug therapy is needed and recommended.
AR has 10%–40% prevalence in the world, which affects many aspects of life and in the public health field, is an ongoing problem. Cold weather is associated with the development of AR, especially for male children and extreme cold temperature is strong trigger of AR especially in children. On the other hand, it was estimated that 48%–74% of the population is affected by heat waves all the world. Therefore, identifying the AR risk factors is important (13, 14).
There are clinical, epidemiological and biological evidences that propose cold air affects to respiratory symptoms and AR (15). Cold weather and inhalation of dry air cause respiratory symptoms in the general population. Cold sensitivity in asthma was further confirmed in clinical provocation studies and during exercise tests in cold weather (16, 17). Wintertime cold temperature is associated with increased exacerbations of asthma. Furthermore, decreased temperature increases symptoms of AR that may have a negative impact on the everyday life quality of people with AR (17). The AR in combination with asthma increase cold weather-related breath shortness even more than asthma alone. On the other side, nasal mucosa drying could lead to hyperosmolality and bronchoconstriction. In the dry air conditions, the mucosal tissue lost humidity and elasticity that may lead to irritation of local nerves and presents clinical symptoms in sneezing form. (16, 17). In this study, cold air and decreased temperature leaded to increased nasal rubbing in AR mice and also, sneezing was increased in the AR mice that were kept in dry air condition. In the cold conditions, mucosal tissue of nasal and upper airways are irritated and the blood circulation may be changed, therefore, lead to clinical symptoms and nasal rubbing. LTB4 and LTC4 levels as main leukotriene and important inflammatory factors, were increased in the AR group mice that were challenged by warm air conditions compared to the AR group without any challenge. Increased temperature may be trigger of the inflammatory factors, especially leukotriene producing pathways such as lipo-oxygenase cycle.
An increase in airway temperature by hot humid air causes immediate and transient bronchoconstriction. These changes are felt by the potential transient receptor type 1 vanilloid receptor (TRPV1), which is also expressed in the sensory nerve fibers of the pharynx, larynx, and upper airways. TRPV is a family of ion channels consisting of 6 membrane domains that form non-selective and non-voltage cation channels and TRPV1-4 is activated in different temperature ranges (18, 19).Some infections such as Linguatula serrata can change expression of some related allergo-inflammatory molecules and immune responses that should be noted in the infected environments, especially in the endemic places (20, 21). Total IgE and IL-4 levels had no significant changes in AR-C, AR-W, AR-H and AR-D groups compared the AR group. The genes of MUC5a and HRH1 were highly expressed in AR mice that were in cold air conditions compared with the AR mice that were in standard air conditions. Moreover, the CysLT1R gene was highly expressed in AR mice that were in warm air conditions compared with the AR mice that were in standard air conditions. Therefore, hot weather conditions not only affect the production of leukotriene, but also the expression of leukotriene receptors. Cold weather conditions also not only increase histamine secretion, but also increase histamine receptor expression. Increase in MUC5a gene showed that cold temperature can increase mucus production and secretion, which leads to excessive mucus secretion and nasal obstruction. Finally, it was observed that air temperature and humidity affect the pathophysiology of AR and can change the molecular pattern of AR. Therefore, climatic conditions can be an important factor in the control and treatment of AR and affect the future appearance of AR.In the future studies, it was suggested that other weather conditions such as pollutions (especially with heavy metals and new syntheses chemical components) on the expression of related genes in AR will be studied. Also, it would be useful that effect of weather conditions on AR pathophysiology will be studied in newborn, young and old populations.