|Year : 2022 | Volume
| Issue : 2 | Page : 62-70
A study on common aeroallergens in a coastal city of south india by skin prick test
Vishnu Sharma Moleyar, Abhishek Bali
Department of Respiratory Medicine, A. J. Institute of Medical Sciences and Research Centre, Mangalore, Karnataka, India
|Date of Submission||12-May-2022|
|Date of Decision||18-Jul-2022|
|Date of Acceptance||28-Aug-2022|
|Date of Web Publication||23-Dec-2022|
Dr. Abhishek Bali
Department of Respiratory Medicine, A. J. Institute of Medical Sciences and Research Centre, Kuntikana, Mangalore, Karnataka
Source of Support: None, Conflict of Interest: None
Introduction: Airborne allergens are the major cause of allergic respiratory diseases worldwide, they are present all around, suspended in the air we breathe, spanning different regions, invisible to the naked eye, while causing allergic respiratory flare-ups in susceptible individuals. Although present globally they have a unique distribution which depends on geographic and climatic factors. Hence, a select broad group of allergens cannot be accountable for causing allergic responses worldwide. It is therefore imperative to identify the offending allergens causing flare-ups in patients living in a particular region, to effectively tackle exacerbations. Objectives of Study: (1) To study the clinical profile of patients with rhinobronchial allergies, (2) To determine endemically common aeroallergens for patients with rhino bronchial allergies from Dakshina Kannada District, presenting at A. J. Institute of Medical Sciences, Mangalore, by means of skin prick test (SPT). Materials and Methods: A total of 170 patients with preexisting allergic airway diseases were included in the study over a duration of 12 months. These subjects were screened, history was taken, and then subjected to an SPT after acquiring an informed consent. A customized panel of 55 allergens was used in the test comprising dust/dust mite, animal, fungal, insect, and plant-based allergens. A wheal size of more than 3 mm was considered as a positive reaction and the findings were recorded. Results: This study included 97 male and 73 female patients, with the mean age of the patients being 33.7 years. The most common aeroallergen was found to be, Parthenium hysterophorus, followed by Dermatophagoides farine a dust mite, Typha angustata, Cyperus Rotundus, Mangifera indica, Ischaemum, and Prosopis juliflora. Cockroach, dog epithelia, and Aspergillus fumigatus were found to be most allergenic in each respective group, i.e., insect, animal, and fungal group. Conclusion: Our study showed predominantly pollen-based allergens from mainly invasive wild grasses and small plants to be causing allergic respiratory diseases in susceptible individuals, especially young adults, living in Dakshina Kannada District, Karnataka. Allergic respiratory diseases due to Dust mite D. Farine were found to cause allergic manifestation in mainly urban population included in the study. A. fumigatus, dog epithelia, and cockroach were found to be the most common antigens causing allergic reactions in each respective category.
Keywords: Aeroallergens, skin prick test, South Indian city
|How to cite this article:|
Moleyar VS, Bali A. A study on common aeroallergens in a coastal city of south india by skin prick test. J Assoc Pulmonologist Tamilnadu 2022;5:62-70
|How to cite this URL:|
Moleyar VS, Bali A. A study on common aeroallergens in a coastal city of south india by skin prick test. J Assoc Pulmonologist Tamilnadu [serial online] 2022 [cited 2023 Jan 27];5:62-70. Available from: http://www.japt.com/text.asp?2022/5/2/62/365077
“If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.”
Sun Tzu, The Art of War
| Introduction|| |
Immune responses to antigens, airborne or otherwise, may sometimes cause unwanted symptoms in the host. The affected host is said to be hypersensitive to these agents, and the responses are referred to as hypersensitivity reactions. Production of immunoglobulin (Ig) E is central to the pathophysiology of allergic diseases such as allergic rhinitis and atopic asthma. After IgE binds to high-affinity mast cell surface FCI receptors and is cross-linked by antigen, mast cell activation occurs and sets in motion a cascade of events resulting in the clinical manifestations of allergic disease.
Allergic respiratory diseases are common throughout the world, spanning all countries and affecting almost 15%–20% of the world population. This imposes a substantial physical and economic burden on the individual in the form of repeated visits to health-care facility and the long medication courses which are followed to keep the allergic flare-up at bay. Some patients have an occasional mild allergic reaction, some react with recurrent or persistent symptoms. Multiple factors contribute to the overall risk of developing allergy. These are atopy, age (more common in children than adults), gender (more common in males than females), family size (less common in large families), smoking, high levels of antigen exposure, and dietary factors. Most often antigens are inhaled, usually triggering more local reactions in the upper or lower respiratory tract (rhinitis or asthma). Asthma and allergic rhinitis are the most common allergic conditions seen in clinical practice.
Aeroallergen with an origin from plants, animals, molds, and mites are the most common allergens involved in asthma and allergic rhinitis. Allergic disorders are diagnosed by a proper history, physical examination, and a detailed clinical examination. Other tests are performed to substantiate the possibility of an allergic respiratory disease. These include serum IgE levels, eosinophil count, allergen-specific IgE, skin prick test (SPT), radioallergosorbent test, and pulmonary function test.
Identifying the airborne allergens and taking measures to avoid them can improve disease control. SPT is a simple, safe, quick, and reliable test to determine allergens affecting individuals and it can be used to advice the patient to avoid exposure to specific offending allergens and also as a guide for immunotherapy for the long-term management of the patient's condition.
Airborne allergens are the major cause of allergic rhinitis and asthma. Airborne allergens may differ in different parts of the world. The distribution of airborne allergens basically depends on geographic and climatic factors. Hence, a select broad group of allergens cannot be accountable for causing allergic responses worldwide. It is therefore imperative to identify the offending allergens in each region to effectively tackle the disease. The identification of airborne allergens is essential in the management of allergic respiratory diseases. Mainstay of the management of allergic asthma includes avoidance of allergens, pharmacotherapy, and immunotherapy. We undertook this study due to a lack of studies on aeroallergens in our region, prevalence of various types of airborne allergens from various sources such as pollen from plants, weed, grasses animal sources, fungi as well as dusts and dust mites, in Dakshina Kannada District, in Karnataka state.
This study was carried out to know the prevalence of various airborne allergens by means of SPT and comprising a panel of allergens which are thought to be prevalent in the region.
| Objectives of study|| |
- To study the clinical profile of patients with rhinobronchial allergies
- To determine endemically common aero allergens for patients with rhino bronchial allergies from Dakshina Kannada district, presenting at A.J. Institute of Medical Sciences, Mangalore, by means of SPT.
| Materials and Methods|| |
For this study, a sample size of 165 patients (Z score of 2.576, P = 0.5, percentage error value of 0.01) were selected, with the age of the patients ranging from 15 to 55 years. These included patients diagnosed to have allergic respiratory diseases namely allergic rhinitis, bronchial asthma, or both. These patients were subjected to a questionnaire based on the 2008 ARIA guidelines and a detailed clinical history was taken following which clinical examination was performed to conclusively diagnose an allergic respiratory disease. This was followed by a spirometry test with the assessment of bronchodilator reversibility to confirm bronchial asthma. These patients were then classified as those having bronchial asthma, allergic rhinitis, or both. Ethical clearance was obtained from institutional ethics committee prior to initiation of the study.
The type of allergic respiratory disease, duration of symptoms, information regarding symptom-free interval, worsening of symptoms on a seasonal basis, and information regarding potential triggers for each patient was also taken into consideration during the process of selection. Patients presenting with acute exacerbations of the disease were excluded from the study as were patients with severe comorbidities. The patients were informed about the SPT for allergic respiratory disease, the procedure of the same, the possibility of adverse allergic reaction to the allergens as well the possibility of a negative outcome of the test due to the patient not having an allergic response to the specific allergens chosen for the panel.
Those patients who were receiving antihistaminic medications, and/or oral corticosteroids were asked to temporarily discontinue the medications as per the guidelines set by the European standards for SPT s due to the potential interference they might have on the test [Table M1]. For candidates with bronchial asthma, who were on inhalation medications at the time of testing, the use of inhalation medication was not discontinued as it could lead to a flare-up of symptoms which would be a contraindication for the proposed study and also because of its effect on the outcome of the study is negligible.
Just before beginning the test, the patients were evaluated and auscultated. Those patients who had some bronchospasm or rhonchi on auscultation of the chest were then subjected to a peak flow meter test to determine their forced expiratory volume 1st s (FEV1) values. If the values were found to be <70% of the normal, the SPT was postponed for the candidate as it is a relative contraindication.
A customized allergen panel comprising 55 different airborne allergens was used in our study. These included allergens from animal, insect, plant, and fungal sources as well as dust mites and various organic dusts. The allergens used in the test were manufactured by CREDISOL®, a division of Creative Diagnostic Medicare Pvt Ltd, Mumbai. The allergen pack was procured institutionally, by A J Institute of Medical Sciences and Research Centre, Mangalore, for use on its patients. Allergen extracts utilized for our SPT had a concentration of 1 ug/ml and were glycerine-free, in order to avoid false-positive reactions. The panel of allergens was created keeping in mind the common flora of the region, the exposure of the inhabitants of the area to the various pollen throughout the year. The date of expiration of the antigens was also frequently checked during conducting the study.
The pollen allergens included were subdivided into:
- Shrubs and
The pollen antigens were selected on the basis of the local flora and plant life which was readily growing in Dakshina Kannada district, Karnataka. Epidemiology of bronchial asthma in the region was also considered while including various fungal antigens. Animal- and insect-based sources such as cat and dog dander, ant- and honeybee-based allergens, and pigeon-based allergens were included in the list of allergens in the panel prepared [Table M2].
Normal saline was used as a negative control while histamine dihydrochloride (0.1%) was used as a positive control while performing the SPT s. Testing was halted in case the patient had a positive skin reaction with normal saline. The antigens used were stored at a controlled temperature which was always regulated constantly between 2°C and 8°C during the duration of the tests. Chances of contamination and dilution were reduced to a minimum using the in-built dropper attached to the cap of every vial of antigen in the panel. The antigen vial was recapped tightly and then stored in its secure box after every test. Contamination was also prevented using a different blood lancet for each of the antigens used.
The procedures were performed on the patients within the confines of the Respiratory Medicine ward at A.J. Institute of Medical Sciences, Mangalore. A written consent form was presented to the patient and signature was taken from the patient before beginning the procedure.
A quick clinical examination was done it was made sure that the candidates had stopped taking anti-histamine medications for the appropriate duration before presentation. The patients with bronchial asthma were subjected to a peak flow meter test to determine FEV1 values at the time of testing and if the FEV1 values were found to be < 70% of the normal value, testing was postponed for later. A crash cart was also kept on standby in case a severe anaphylactic reaction was encountered. The ventral aspect of the arm was used for performing the tests. The area was swabbed clean using a solution of isopropyl alcohol and 2.5% chlorhexidine solution. A skin marking pen was used to mark out the various antigen drop placement locations on the skin. 0.1 ml of the antigen solution was placed on the skin and then the skin was lightly punctured with a single head disposable lancet. Care was taken to avoid bleeding as it can lead to incorrect readings. A different lancet was used for each antigen, to prevent cross-contamination and to maintain reproducibility.
After all the allergens had been introduced to the skin and pricked with the lancet, the testing site was observed for any local reaction to the different antigens in the form of a wheal formation or a flare. Although the skin reactions may start appearing immediately after the prick and may peak 8–10 min after performing the test, the readings were recorded officially 15–20 min after application. A timer with stopwatch was used to keep track of the time. The wheal size was measured using a Vernier caliper then graded on wheal size as seen in the table below. A wheal size larger than 3 mm was considered a positive reaction.
Patients were observed postprocedure and were instructed to immediately report and discomfort such as breathing difficulty, excessive lacrimation, chest discomfort, or severe itching among others as well as any delayed anaphylactic responses. After an observation period of 4 h, signs of a delayed reaction were noted, and then, the patients were discharged with a copy of the test result written in their outpatient book.
| Results|| |
Our study was conducted on a total of 165 patients who were diagnosed to have either allergic rhinitis or bronchial asthma or both. The tests for skin prick sensitivity to allergens were carried out on an outpatient basis in the Department of Respiratory Medicine, A.J. Institute of Medical Sciences, which is a Tertiary Level Referral Teaching Hospital, located in the city of Mangalore, Karnataka.
The study was started on December 01, 2016, and was concluded on November 30, 2017, with 12 months.
The study included a total of 165 individuals who were selected on the basis of their symptoms, clinical history, and a previous diagnosis of allergic airway disease such as allergic rhinitis or bronchial asthma or both. Out of a total of 165 patients, the subjects comprised 68 females and 97 males.
The ages of the candidates included in our study ranged from 15 to 55 years of age (Mean 33.7 years) [Figure 1].
|Figure 1: Graphical representation of the number of patients in each age group|
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The patients were subdivided into groups based on their age group for a better understanding of the distribution of allergic airway diseases in patients across the different ages. In terms of the distribution of the patients in each age group, our study showed that 28.2% of the patients (n = 46) were from the age group of 25–34 years, while 27% (n = 46) were from the age group of 15–24 years. The total number of patients from each age group is described in [Table 1]. The least number of candidates was the 45–55 years of age group. This demonstrates that mainly young adults were more affected by allergic airway diseases than the elderly.
|Table 1: The distribution of patients in each age group out of a total number of 165 patients|
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Distribution based on gender
Our study included a total of 170 patients out of which 73 were female and 97 were male patients with allergic airway disease, who presented to the respiratory medicine outpatient department at A.J. Institute of Medical Sciences and Research Centre [Figure 2] and [Table 2].
|Figure 2: Venn diagram representing the number of patients with bronchial asthma, allergic rhinitis or both as represented by the area of the two circles and the overlapped|
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|Table 2: The statistical data of the ages of the patients included in the study|
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Distribution based on domicile type
The patients were further classified according to their area of residence into those living in rural areas and those living in urban areas. This was done as the patients living in different areas, urban or rural, would be exposed to different allergens specific to that area. In our study, 64.8% (a total of 107 patients out of 165) of the patients were found to be from urban areas while 35.15% (58 out of 165 patients) were found to be from a rural area of residence [Figure 2] and [Table 3].
Distribution based on clinical history
Out of the 165 patients under study 77 patients were diagnosed with cases of bronchial asthma without allergic rhinitis while 59 patients were diagnosed to be cases of allergic rhinitis without allergic airway disease. Twenty-nine patients out of 170 were cases of allergic rhinitis with bronchial asthma as is represented by the Venn diagram [Figure 3] and [Table 3].
|Figure 3: Graphical representation of the number of patients included in the study based on domicile type and gender. Fifty one patients out of 170 lived in a rural location while 119 patients lived in urban areas. Key to graph: R = Rural domicile, U = Urban domicile, F = Females, M = Males|
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Each of the patients was subjected to a SPT after acquiring an informed consent from them. The tests, which were performed as per the Department's protocol in accordance with the standards set forth by the European standards of skin prick testing. None of the 170 patients had a negative result on SPT and all patients showed a response to subcutaneous injection of histamine di-hydrochloride with the presence of a wheal formation more than 3 mm. All the patients exhibited a positive reaction for more than one allergen. A wheal size of more than 3 mm size was considered as a positive response to the allergen, which was then recorded. No serious anaphylactic adverse effects were seen in the patients under the study. Various endemically important allergens were grouped based on source (pollen, animal, insect, etc.,) and the percentage of positive reaction among the total number of patients, to each allergen, in each group was recorded. A wheal size <3 mm was not considered significant.
A selected panel of allergens from plants, grasses, and trees was used for our study. The allergens from pollen extracts that had the highest frequency of positive response are listed in [Table 4].
|Table 4: Pollen-based allergens with the highest percentage of positive reactions on skin prick test|
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Our study found grass pollens to be most allergenic in the patients included in our study. Pollens of grasses Parthenium hysterophorus, Typha Angustata and Cyperus rotondus were found to have the highest frequency of allergic reactions in our patients at 28.21% and 24.1%, respectively. Ageratum conyzoides, a weed was found to have least frequency of positive response. Most of the pollen allergens which gave a positive response were native to the region and were a part of the local wild flora. The bar graph listing the percentage of positive response of each pollen allergen in the patients under study is given in [Figure 4].
|Figure 4: A representation of the different allergens used in the panel from pollen-based source versus the percentage of positive reaction on SPT. SPT = Skin prick test|
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Dusts and dust mite
Our study found the female dust mite Dermatophagoides farinea to have the highest frequency among the patients under study affecting 26.20% of the subjects. The percentage of positive reactions of the other pollen-based allergens is listed in [Table 5] and [Figure 5].
|Table 5: Allergens from dusts and dust mite group and their frequency of positive reaction|
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|Figure 5: A representation of the various dusts and dust mite based allergens and the percentage of positive reactions based on the SPT. Highest percentage of positive reaction being noted in D. farine and the least percentage of positive reaction. SPT = Skin prick test, D. farina = Dermatophagoides farinae|
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Fungi and molds
Among fungal- and mold-based antigens, Aspergillus fumigatus recorded the highest frequency of 21.76% followed by Aspergillus niger at 18.70%, Aspergillus flavus at 17.20%, and Rhizopus nigracans indica at 15.80% [Figure 6]. Alternaria alternata was found to have the least frequency at 2.30%. The SPT for fungal allergens was found to be positive in 75% of patients with underlying bronchial asthma.
|Figure 6: Graphical representation of the most prevalent allergens in the fungi group. The frequency of positive reaction among the patients under study is represented as the percentage value|
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Among insect-based allergens, a cockroach was most predominantly seen to cause a positive reaction at 21.70% (n = 170), while honeybee antigen had the least percentage of positive reaction at 3.50% (n = 6). The relative percentages of all antigens are listed in [Figure 7].
|Figure 7: Graph depicting the percentage of positive reaction of insect based allergen among test subjects. Cockroach antigen was found to be most reactive among the other allergens in this category|
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Our study found dog dander to cause a positive reaction in 18.23% of the subjects included in the study (n = 31) while pigeon feather had the least incidence [Table 6]. The incidence of the rest of the animal-based antigens is listed in [Figure 8] and [Table 7]. Of the 31 patients who were found sensitive to dog dander, only 8 had dogs as pets in their residence as was discovered after performing the SPT.
|Table 6: The most reactive antigens in each of the sub groups of dusts, mites, fungi, animal, insect and pollen sources and the percentage of positive reactions in the patients|
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|Figure 8: Representation of the percentage of positive reactions on skin prick test using allergens of animal origin|
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|Table 7: Showing the most reactive antigens in each of the sub groups of dusts, mites, fungi, animal, insect and pollen sources and the percentage of positive reactions in the patients|
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| Discussion|| |
Worldwide an estimated 300 million individuals, of different age groups are affected by asthma. It is estimated that 30% of adults and 40% of children are affected by allergic rhinitis with global trends showing an increase in the numbers annually. Asthma may coexist with allergic rhinitis in the same patient as there is a high association between the two. In some cases, suboptimally managed allergic rhinitis may cause asthma exacerbations, thereby increasing the burden of asthma.
The most important cause of these exacerbations in asthma and allergic rhinitis are aeroallergens. These aeroallergens are small particles which are present in the air, and after being released from various sources such as plant pollen, fungi, and animals, make their way into the respiratory tract, causing a cascade of events leading to an exacerbation. However, it must be noted that the distribution of the type of allergens is not universally the same. It varies from place to place, having a geographic, endemic, and region-specific distribution.
Our study included 165 patients of either kind of allergic airway disease (bronchial asthma and allergic rhinitis) comprising 97 males and 58 females with the ages of the subjects ranging from 15 to 55 years (mean age 33.7 years). These subjects were further subclassified into those who lived in an urban environment and those who lived in a rural environment. This was done to identify the different causes of airborne allergies affecting the people from various areas if any.
Our study found a higher incidence of allergic rhinitis and asthma in the urban population. A study conducted by Nicolai et al. on the effects of urban environment in the development of atopy and respiratory allergies in children, found that high levels of vehicle emissions and the presence of suspended particulate matter in urban areas leads to an increased prevalence of atopy and respiratory allergies. A higher proportion of patients with allergic airway disease were found to be from the urban areas which was in agreement with our study.
In our study, the patterns of positive skin prick reaction revealed pollen allergies, (especially grasses and plants) being more common in the urban population. This could be attributed to decreased exposure to pollens in the early childhood. Children in an urban area tend to play less outdoors and spend less time outdoors. Lack of exposure to various aeroallergens increases the risk of developing sensitization when exposed in later life. A similar study conducted by Ege et al. demonstrated that children raised and living on a farm have less hay fever, asthma, and allergic sensitization indicating that the pollen-based allergens present in rural areas tend to cause fewer allergies in the population. This was also found true in our study which found dust mite, tree, and insect-based antigens were found to be more in the rural patients.
The most prevalent causes of allergy in our study population belonged to the pollen group namely P. hysterophorus (28.2%) which is a variety of highly invasive flowering weed, present in the wild and near cultivated fields in Dakshina Kannada District. This is due to the fact that Dakshina Kannada District is rich in greenery even within the urban areas and wild varieties of grasses are found in abundance, in close proximity to the residential areas. The other pollen-based allergens which were found positive in a number of individuals was Cyperus Rotudus, another species of wild grass (24.10%), while among small plants Typha angustifolia, a wild plant (25.29%), and Prosopis juliflora (22.94%) were found to be common causes of allergic reactions. Our study found predominantly wild grasses and plants which are invasive in nature as the main causes of allergic flare-ups when compared to other plants included in the study. Clearing off the offending wild vegetation would therefore help in the avoidance of the pollens and thus reduce the incidence of flare up of respiratory diseases in the susceptible patients.
Among dust and dust mites, the most common cause of allergic airway disease was found to be a dust mite, particularly D. farine affecting 26.20% of the subjects included in the study, and D pteronyssinus, found to be positive in 20.60% of the subjects, particularly in urban residents and caused perineal symptoms in the said group of patients. The most common dust to cause a positive reaction in our study was Spider web dust accounting for 22.30% of positive skin responses.
The most predominant insect to show a positive response was cockroach at 21.70%. While in the fungal group A. Fumigatus was the most prevalent (21.76%), followed by A. niger (18.76%) and A. Flavus (18.76%). A higher degree of sensitization to fungal spores and molds was observed in patients of asthma, compared to those with allergic rhinitis alone.
The least number of positive skin reactions were seen in the animal group in which dog epithelia topped the list at 18.23%. This could be due to the fact that most of the patients did not have any close interaction with the animals or birds and only 24 patients either had pets or were exposed to animals/birds at work.
It was also noted that the maximum number of patients, 49% (N = 170) in whom a positive skin reaction was seen, belonged to the age group of 25–34 years. This showed that young adults were more likely to be exposed to the allergens as a part of their daily life as compared to the people of other age groups. The next age group to be most affected was found to be the 15–24 years accounting for 46% of the subjects with positive SPT for aeroallergens. These are the two age groups that would have the highest exposure to the allergens while being engaged in household chores like dusting, while working outside or while traveling to and from work or school.
Our study endeavored to determine the prevalent aeroallergens and help the patients in identifying the offending allergen, avoiding those which can be easily avoided like pollens and dust mite through simple and yet effective measures. The identification of offending allergens also helps avoidance of the offending allergen and in the initiation of targeted immunotherapy to effectively sensitize the patient to the said allergen. These along with pharmacotherapy help to relieve the symptoms of allergic respiratory diseases, effectively reduce the symptoms, frequency of exacerbations, reduce the morbidity associated with these conditions and improves the quality of life of the patient.
| Conclusion|| |
Our study showed a predominantly pollen from grass and plant of the wild, invasive kind, followed by dust mites to be the most common sources of aeroallergens prevalent among the subjects, with the highest incidence seen in young adults in the age group of 25–34 years living in Dakshina Kannada District, Karnataka. Allergic respiratory diseases due to Dust mite D. Farine was found to cause allergic manifestation in mainly urban population. A. Fumigatus, dog epithelia, and cockroach were found to be the most common antigens causing allergic reactions in each respective category.
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Conflicts of interest
There are no conflicts of interest.
| References|| |
National Heart, Lung, and Blood Institute. Guidelines for the Diagnosis and Management of Asthma. NIH Asthma Expert Panel Report. Bethesda, MD: National Heart, Lung, and Blood Institute; 1991.
Johnson CC, Ownby DR, Zoratti EM, Alford SH, Williams LK, Joseph CL. Environmental epidemiology of pediatric asthma and allergy. Epidemiol Rev 2002;24:154-75.
Settipane RJ, Hagy GW, Settipane GA. Long-term risk factors for developing asthma and allergic rhinitis: A 23-year follow-up study of college students. Allergy Proc 1994;15:21-5.
Howarth PH, von Mutius E, Martinez FD. Allergic and non allergic rhinitis. Natural history, development and prevention of allergic disease in childhood. In: Middleton's Allergy Principles and Practice. USA: Mosbey; 2003. p. 1391-407.
Grossman J. One air way, one Disease: Chest 1997;111 suppl 1:11-6.
Heinzerling L, Mari A, Bergmann KC, Bresciani M, Burbach G, Darsow U, et al.
The skin prick test – European standards. Clin Transl Allergy 2013;3:3.
Flora of South Kanara: Dakshina Kannada and Udupi Districts of Karnataka. Udupi, India: K. Gopalakrishna Bhat. 'Madhuca', Srinivasa Nagara, Chitpady; 2014. p. 928.
Piette V, Bourret E, Bousquet J, Demoly P. Prick tests to aeroallergens: Is it possible simply to wipe the device between tests? Allergy 2002;57:940-2.
Oppenheimer J, Nelson HS. Skin testing. Ann Allergy Asthma Immunol 2006;96:S6-12.
Konstantinou GN, Bousquet PJ, Zuberbier T, Papadopoulos NG. The longest wheal diameter is the optimal measurement for the evaluation of skin prick tests. Int Arch Allergy Immunol 2010;151:343-5.
Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema: ISAAC. The International Study of Asthma and Allergies in Childhood (ISAAC) Steering Committee. Lancet 1998;351:1225-32. PMID: 9643741.
Nicolai T, Carr D, Weiland SK, et al
. Urban traffic and pollutant exposure related to respiratory outcomes and atopy in a large sample of children. Eur Respir J 2003;21:956-963. doi:10.1183/09031936.03.00041103a.
Bosch-Cano F, Bernard N, Sudre B, et al
. Human exposure to allergenic pollens: A comparison between urban and rural areas. Environ Res 2011;111:619-25. doi:10.1016/j.envres.2011.04.001.
Ege MJ, Bieli C, Frei R, van Strien RT, Riedler J, Ublagger E, et al
. Parsifal Study team. Prenatal farm exposure is related to the expression of receptors of the innate immunity and to atopic sensitization in school-age children. J Allergy Clin Immunol. 2006 Apr;117(4):817-23. doi: 10.1016/j.jaci.2005.12.1307. Epub 2006 Feb 7. PMID: 16630939.
Sharma VK, Verma P. Parthenium dermatitis in India: Past, present and future. Indian J Dermatol Venereol Leprol 2012;78:560-8. [Full text]
Hussain MI, Shackleton RT, El-Keblawy A, Del Mar Trigo Pérez M, González L. Invasive Mesquite (Prosopis juliflora), an Allergy and Health Challenge. Plants (Basel) 2020;9:141. doi: 10.3390/plants9020141. PMID: 31979176; PMCID: PMC7076653.
Denning DW, Pashley C, Hartl D, Wardlaw A, Godet C, Del Giacco S, et al
. Fungal allergy in asthma-state of the art and research needs. Clin Transl Allergy 2014;4:14. doi: 10.1186/2045-7022-4-14. PMID: 24735832; PMCID: PMC4005466.
Zahradnik E, Raulf M. Animal allergens and their presence in the environment. Front Immunol 2014;5:76. doi: 10.3389/fimmu.2014.00076. PMID: 24624129; PMCID: PMC3939690.
Larsen JN, Broge L, Jacobi H. Allergy immunotherapy: the future of allergy treatment. Drug Discov Today 2016;21:26-37. doi: 10.1016/j.drudis.2015.07.010. Epub 2015 Sep 2. PMID: 26327511.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]