Sultan Qaboos Univ Med J 8(3): 319-324

PMC: PMC3074841

PMID: 21748078

The Pattern of Sensitisation to Inhalant Allergens in Omani Patients with Asthma, Allergic Rhinitis and Rhinoconjunctivitis

Objective:

Identification of relevant allergens that are prevalent in each environment which may have diagnostic and therapeutic implications in allergic diseases. This study aimed to identify the pattern of sensitisation to inhalant allergens in Omani patients with asthma, allergic rhinitis and rhinoconjunctivitis.

Methods:

The study was carried out during three consecutive years (2004–2006) at the allergy skin test laboratory of Sultan Qaboos University Hospital, Oman. Records of patients who had undergone an allergy skin prick test with a referring diagnosis of asthma, allergic rhinitis or rhinoconjunctivitis were reviewed. Two panels were used during the 3 years period. The frequencies of positive skin tests were analysed.

Results:

689 patients were tested, 384 for the first panel and 305 for the second panel. In the first panel, the commonest positive allergens were: house dust mites (37.8%), hay dust (35.4%), feathers (33.3%), sheep wool (26.6%), mixed threshing dust (25.8%), cat fur (24.2%), cockroach (22.7%), straw dust (22.7%), horse hair (17.4%), maize (16.1%), grasses (11.5%), cotton flock (10.7%), trees (10.4%), cow hair (7.8%), Alternaria alternata (3.6%), Aspergillus Niger (3.4%), and Aspergillus fumigatus (1.3%). In the second panel, the commonest positive allergens were also house dust mites: Dermatophagoides pteronyssinus (50.8%), Dermatophagoides farinae (47.9%); Mesquite (Prosopis glandulosa) (35.7%), Russian thistle (Salsola kali) (34.4%), cockroach (32.1%), Bermuda grass (Cynodon dactylon) (19.7%), grass mix-five standard (18.0%), wheat cultivate (14.1%), cats (13.8%), Penicillium notatum (4.3%), Alternaria tenius (3.9%), Aspergillus Niger (3.3%), feather mix (3.0%), dog (2.6%), horse hair and dander (2.6%), and Aspergillus fumigatus (1.6%).

Conclusion:

The pattern of sensitisation to environmental allergens in Oman seems to be similar to other reports from the Arabian Peninsula. Methods to identify and characterise environment specific allergens like a pollen survey may help in the management of patients with allergic asthma, allergic rhinitis and rhinoconjunctivitis.

METHODS

Medical records of allergy skin tests of patients with a referring diagnosis of asthma, or allergic rhinitis or rhinoconjunctivitis for three consecutive years 2004–2006 were reviewed. The patients had been referred to the allergy skin test laboratory from the pulmonary, ENT, child health, and other clinics at Sultan Qaboos University Hospital (SQUH) and Ministry of Health hospitals in Oman. SQUH is the referral centre for allergy skin testing for the whole country. The allergy laboratory is supervised by pulmonologists and recently by an allergist. Patients consents verbally for the skin prick tests.

There were two panels of extracts used during the three year period, bought from two different companies, and represented by two different graphs in the results. The panel of allergens used consisted of common inhalant allergens believed to be of significance. In the first period, the extracts used were bought from Bencard Company. In the second period, the extracts used were bought from Allergy Laboratories, Inc., USA. Skin prick tests were performed by qualified technicians according to standard method.17 Disposable Greenlan needles, lancet 23G, were used to prick the skin. Histamine positive control and diluent negative control were used. A skin test was considered positive when a wheal was 3 mm greater than the negative control. Eight patients (7 from the first period and 1 from the second period) were not included in the analysis as they had negative histamine control; none tested positive for negative control.

Using the Statistical Package for the Social Sciences (SPSS), data were entered into two different sheets. For the analysis of baseline characteristics, the data were combined and frequencies were calculated. The two panels of allergens were analysed separately, as they are different and the frequencies were calculated.

RESULTS

There were a total of 689 patients with asthma, allergic rhinitis and rhinoconjuctivitis tested during the study period. A total of 384 were tested for the first panel and 305 for the second panel. The youngest patient was 5 years old and the oldest 81 years old; the median age was 30 years. The majority of patients were referred from the chest and ENT clinics. Of the patients tested, 39.2% had a diagnosis of asthma, 61.3% allergic rhinitis and 1.9% rhinoconjuctivitis. Baseline data are summarised in Table 1.

Table 1:

Patient data

	Number = 689	Percentage %
Age Category
< 12 years	28	4.1
≥ 12 years	661	95.9
Sex
Male	314	45.6
Female	375	54.4
Nationality
Omani	635	92.2
Non-Omani	54	7.8
Referring Clinic
Chest	264	38.3
ENT	327	47.5
Child Health	9	1.3
Ophthalmology	1	0.1
Other	88	12.8
Diagnosis
Asthma	271	39.3
Allergic rhinitis	420	61.0
Rhinoconjuctivitis	13	1.9

During the first period [Figure 1], the commonest positive allergen was house dust mites with 37.8% of patients being sensitis ed, hay dust (35.4%), straw dust (22.7%), mixed threshing dust (25.8%), grasses (11.5%) (in 11 cases the extract was not available), trees (10.4%), maize (16.1%), cotton flock (10.7%), animal allergens, sheep wool (26.6%), horse hair (17.4%), cat fur (24.2%), cow hair (7.8%), feathers (33.3%), cockroaches (22.7%) (in 19 cases the extract was not available); mould allergens: Alternaria alternata (3.6%), Aspergillus Niger (3.4%), and Aspergillus fumigatus (1.3%).

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Object name is squmj-08-319f1.jpg

Figure 1:

Number of patients with positive tests and cumulative percentage of positive tests during the first period

During the second period [Figure 2], the commonest positive allergens were also house dust mites: Dermatophagoides pteronyssinus (50.8%), Dermatophagoides farinae (47.9%); pollen allergens: mesquite (Prosopis glandulosa) (35.7%), Russian thistle (Salsola kali) (34.4%), Bermuda grass (Cynodon dactylon) (19.7%), grass mix-five standard (18.0%) and wheat cultivate (14.1%) [in 2 cases the extracts were not available]; animal allergens: cat (13.8%), dog (2.6%), horse hair and dander (2.6%), feather mix 3.0%; moulds: Aspergillus Niger (3.3%), Aspergillus fumigatus (1.6%), Penicillium notatum (4.3%) [in 11 cases the extract was not available] and Alternaria tenius (3.9%) and cockroach (32.1%).

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Object name is squmj-08-319f2.jpg

Figure 2:

Number of patients with positive tests and cumulative percentage of positive tests during the second period

DISCUSSION

In this study, we are able to demonstrate that house dust mites are the commonest sensitisation in Omani patients; half of all patients were sensitised to them which is in agreement with other studies conducted on asthmatic patients elsewhere.18 About one third of patients were sensitised to mesquite tree and Russian thistle, both common plants in Oman. Grasses contributed to 10% of cases. However, there are other plants in Oman that are potentially allergenic like date palm (phoenix dactylifera), a widely planted tree in Oman, for which it may be necessary to test. The families of Chenopodiaceous and Compositae plants both exist in Oman and may contribute to sensitising agents. Hay dust, straw dust and mixed threshing contributed to about one third in the first period, but these were not individual allergens. One third of patients were sensitised to cockroaches implicating a significant contribution.

In Oman, animals are not often allowed into houses, but sometimes there are domestic cats and dogs that stay around houses and people might get exposed to their allergens. Horses are mainly raised in stables and exposure might be limited to people that work with them. The difference in rate of sensitisation between the two panels could be because of lack of standardised allergen extracts from different manufacturers. Some people raise cattle, goat and sheep in small farms attached to the backyard of their houses. Pigeons are found in Oman; it is not a common practice to keep them inside houses, however exposure to their feathers is still possible as they nest on buildings. There were more patients sensitised to animals and birds in the first period than in the second period. This might be due to variation in allergen extracts because of lack of standardised allergens made by different manufacturers. Goats are raised in Omani farms and sometimes close to houses therefore it might be an important allergen that should be tested in conjunction with sheep. In general, not all patients necessarily need to be tested unless there is a history of exposure or ownership of a certain animal or bird.

Oman is a warm country with a dry weather, except in the coastal area where it may be humid in the summer. Houses are usually exposed to sun all year around and well ventilated, and usually there are no basements. Moulds grow in humid places and are well known to cause allergies; their environmental control might be more amenable than other allergens and immunotherapy is readily available, hence all patients should be tested. In both study periods, they did not contribute significantly in patients tested; however, it might be useful to use mixtures of moulds rather than individual ones to minimise skin pricks and, if immunotherapy is contemplated, individual moulds could then be tested.

CONCLUSION

The pattern of sensitisation to environmental allergens in Oman seems to be more or less similar to other reports published from Arabian Peninsula. Methods to identify and characterise unique allergens through a pollen survey may still be necessary. This will help in the management of patients with asthma and rhinoconjuctivitis who are sensitised to environmental allergens and may benefit from environmental control measures and immunotherapy.

^{Departments of Child Health}

^Surgery

^{Clinical Physiology, Sultan Qaboos University Hospital, Muscat, Sultanate of Oman;}

^{Department of Medicine, College of Medicine & Health Sciences, Sultan Qaboos University, Muscat, Sultanate of Oman}

^{To whom correspondence should be addressed. Email:}mo.ude.uqs@imemat

Received 2008 Feb 26; Accepted 2008 May 8.

Abstract

Objective:

Methods:

Results:

Conclusion:

Keywords: Asthma, Allergic, Rhinitis, Conjunctivitis, Allergens, Skin tests, Oman

Abstract

Advances in Knowledge

Environmental allergens are well identified and characterised in Western countries, but only a few reports have been published on environmental allergies from the Arabian Peninsula, mainly from Kuwait and Saudi Arabia.
Each environment may have unique allergens that may contribute to the pathogenesis of allergic diseases.
This paper highlights the pattern of sensitisation in Omani patients with asthma, allergic rhinitis and rhinoconjunctivitis,
The common and uncommon allergens are identified for skin testing in Omani patients. This opens up the potential for other allergens to be included in the panel of skin testing.

Application to Patient Care

Patients should be tested with a panel of allergen extracts that would identify the highest number of sensitising agents that may contribute to their allergic disease; hence measures could be instituted to avoid exposure to the responsible allergens.
Immunotherapy for allergic diseases is dependent on identifying the sensitising agents.
This can make postoperative management more specific and result oriented.

Environmental allergens are important immunopathogens that contribute to the pathophysiology of allergic diseases represented mainly by bronchial asthma, allergic rhinitis and rhinoconjuctivitis. It is very important to identify the most relevant allergens in each environment as they differ from one to another. This has diagnostic and therapeutic implications. These patients may benefit from environmental allergen control measures and, where medical therapy is not sufficient to control their symptoms, immunotherapy might be beneficial; hence, the identification of allergens is vital.

Atopy is the tendency of an individual to develop specific IgE against common allergens in the environment. IgE mediates the early phase response of an allergic reaction by involving mast cells as an effecter cell that release chemical mediators which are responsible for the clinical features of an allergic reaction.1, 2 Asthma is a worldwide problem that affects around 10–15% of all populations. In Omani children, as assessed by ISAAC study, the prevalence rates of reported diagnoses of asthma and allergic rhinitis were higher in older children, 20.7% and 10.5%, compared with 10.5% and 7.4% respectively, in younger children.3 Asthma is a chronic inflammatory airway disease characterised by the presence of inflammatory cells and cytokines in the airway mucosa that lead to inflammation responsible for the symptoms of asthma. The etiology of asthma is multifactorial, the role of allergy in asthma is well established; for example, there is a strong link between house dust mites (HDM) sensitisation and the development of asthma.4, 5 Allergic rhinitis is a common medical condition characterised by nasal, throat, and ocular itching; rhinorrhea; sneezing; nasal congestion and, less frequently, coughing. Patients could be sensitised to perennial or seasonal allergens that are present in the environment. Patients with allergic rhinitis may benefit from specific immunotherapy in case medical treatment is insufficient to control their symptoms.6, 7, 8 There is now evidence supporting a link between asthma and allergic rhinitis which may have therapeutic implications.9 Most of the experience of environmental allergies comes from the Western hemisphere. There are several studies conducted in neighbouring countries which have shown a different pattern of allergies from the West.10–15 Little is known about the pattern of environmental allergies in Oman.16 The aim of this study was to identify the pattern of sensitisation to inhalant allergens in Omani patients with asthma, allergic rhinitis and rhinoconjunctivitis.

Acknowledgments

This study was approved by the Institutional Review Board (Scientific & Ethics Committee) of College of Medicine at Sultan Qaboos University

Acknowledgments

REFERENCES

References

1. Arshad SH, Karmaus W, Matthews S, Mealy B, Dean T, Frischer T, et al. SPACE study group (Study of Prevention of Allergy in Children of Europe). Association of allergy-related symptoms with sensitisation to common allergens in an adult European population. J Investig Allergol Clin Immunol. 2001;11:94–102.[PubMed]
2. Arshad SH, Tariq SM, Matthews S, Hakim ESensitization to common allergens and its association with allergic disorders at age 4 years: a whole population birth cohort study. Pediatrics. 2001;108:E33.[PubMed][Google Scholar]
3. Al-Riyami BM, Al-Rawas OA, Al-Riyami AA, Jasim LG, Mohammed AJA relatively high prevalence and severity of asthma, allergic rhinitis and atopic eczema in schoolchildren in the Sultanate of Oman. Respirol. 2003;8:69–76.[PubMed][Google Scholar]
4. Johnson JR, Wiley RE, Fattouh R, Swirski FK, Gajewska BU, Coyle AJ, et al Continuous exposure to house dust mite elicits chronic airway inflammation and structural remodeling. Am J Respir Crit Care Med. 2004;169:378–385. Epub Nov 2003. [[PubMed][Google Scholar]
5. Arshad SH, Hamilton RG, Adkinson NF., Jr Repeated aerosol exposure to small doses of allergenA model for chronic allergic asthma. Am J Respir Crit Care Med. 1998;157:1900–1906.[PubMed][Google Scholar]
6. Hellings PW, Fokkens WJAllergic rhinitis and its impact on otorhinolaryngology. Allergy. 2006;61:656–664.[PubMed][Google Scholar]
7. Frew AJ, Powell RJ, Corrigan CJ, Durham SREfficacy and safety of specific immunotherapy with SQ allergen extract in treatment-resistant seasonal allergic rhinoconjunctivitis. Allergy Clinic Immunol. 2006;117:319–325.[PubMed][Google Scholar]
8. Varney VA, Tabbah K, Mavroleon G, Frew AJUsefulness of specific immunotherapy in patients with severe perennial allergic rhinitis induced by house dust mite: a double-blind, randomized, placebo-controlled trial. Clin Exp Allergy. 2003;33:1076–1082.[PubMed][Google Scholar]
9. Sale R, Silvestri M, Battistini E, Defilippi AC, Sabatini F, Pecora S, et al Nasal inflammation and bronchial reactivity to methacholine in atopic children with respiratory symptoms. Allergy. 2003;58:1171–1175.[PubMed][Google Scholar]
10. Al-Dowaisan A, Fakim N, Khan MR, Arifhodzic N, Panicker R, Hanoon A, et al Salsola pollen as a predominant cause of respiratory allergies in Kuwait. Ann Allergy Asthma Immunol. 2004;92:262–267.[PubMed][Google Scholar]
11. Behbehani N, Arifhodzic N, Al-Mousawi M, Marafie S, Ashkanani L, Moussa M, et al The seasonal variation in allergic rhinitis and its correlation with outdoor allergens in Kuwait. Int Arch Allergy Immunol. 2004;133:164–167. Epub Feb 2004. [[PubMed][Google Scholar]
12. Al Mousawi M, Behbehani N, Arifhodzic N, Lovel H, Woodcock A, Custovic AEnvironmental allergens in Kuwait. Allergy. 2001;56:1237–1238.[PubMed][Google Scholar]
13. Ezeamuzie CI, Thomson MS, Al-Ali S, Dowaisan A, Khan M, Hijazi ZAsthma in the desert: spectrum of the sensitising aeroallergens. Allergy. 2000;55:157–162.[PubMed][Google Scholar]
14. Kwaasi AA, Parhar RS, Harfi H, Tipirneni P, Al-Sedairy ST. Major allergens of date palm (Phoenix dactylifera L.) pollen. Identification of IgE-binding components by ELISA and immunoblot analysis. Allergy. 1993;48:511–518.[PubMed]
15. Al-Nahdi M, Al-Quorain AASex distribution and common allergens of bronchial asthma in a Saudi Arabian (eastern province) population. Allergol Immunopathol (Madr) 1987;15:389–391.[PubMed][Google Scholar]
16. Al-Amri M, Al-Rawas OA, Al-Riyami BMS, Richens ERAtopy in Omani patients with asthma. SQUJ Sci Res Med Sci. 2002;4:15–23.[Google Scholar]
17. Skin tests used in type I allergy testing position paper. EAACI. Sub-committee on skin tests of the European Academy of Allergology and Clinical Immunology. Allergy. 1989;44:1–59.[PubMed]
18. Dibek ME, Reha CMSkin prick test results of child patients diagnosed with bronchial asthma. Allergol Immunopathol (Madr) 2007;35:21–24.[PubMed][Google Scholar]