R espiratory disorders such as asthma and allergic rhinitis are common in the United Arab Emirates (UAE). In a study of 850 schoolchildren, the prevalences of diagnosed asthma and allergic rhinitis were 13.6% and 22.9%, respectively ( 1). The present study aimed to obtain basic data on prick test reactivity to inhalant allergens and to construct a prick test series suitable for local use. To accomplish this, patients with allergy-like respiratory disorders were prick-tested with a panel of inhalant allergens.
This study was carried out in the Allergy Clinic of Tawam Hospital, Al Ain, Emirate of Abu Dhabi, UAE. The study population comprised 249 patients (146 females, mean age and range 28.4, 6–62 years, respectively) who suffered from nasal, conjunctival, or chest symptoms.
The patients were prick-tested by a standard technique. The prick test series changed somewhat with time, but the latest version included the allergens listed in Table 1. The allergens were purchased from Stallergènes, Fresnes Cedex, France, or from Bayer, Spokane, WA, USA. A prick test reaction was defined as positive if it gave a wheal with an area of at least 7 mm2 (corresponding to a wheal diameter of 3 mm) and if the area of the wheal was at least half of that of the positive control (10 mg/ml histamine).
(no. positive of those tested)
|Natural rubber latex||1.0 (1/105)|
|Cockroach mix||14.7 (28/190)|
|D. pteronyssinus||17.1 (38/222)|
|D. farinae||9.5 (21/221)||0.432|
|Cat dander||9.4 (21/223)|
|Goat dander||14.6 (19/130)|
|Feather mix||7.1 (6/85)|
|Camel hair and dander||5.9 (3/51)|
|Bermuda grass||31.3 (74/238)|
|Grass mix||40.7 (22/54)||0.614|
|Russian thistle||48.2 (119/247)|
|Sea blite||43.8 (67/153)||0.714|
|Scale mix||32.9 (26/79)||0.383|
|Pigweed mix||44.3 (27/61)||0.572|
|Date palm||13.8 (8/58)|
|Mesquite tree||45.5 (80/176)|
|Golden acacia||25.6 (11/43)||0.754|
|Aspergillus mix||7.3 (4/55)|
|Penicillium mix||3.9 (2/51)|
The concordance of prick test reactions among various representatives of taxonomically related species was estimated by calculating the kappa coefficient.
The results of the prick tests are shown in Table 1. Sensitization was common to the pollens of chenopods (Russian thistle, lamb's-quarters, firebush, sea blite, and scales), pigweeds, grasses, and legumes (mesquite tree, golden acacia, and alfalfa). Table 1 also shows how compatible prick test reactions were to taxonomically related species.
The family Chenopodiaceae is well represented in the UAE. Most local chenopods are perennial bushes called saltbush. In accordance with previous reports from Kuwait ( 2) and Saudi Arabia ( 3), chenopods seem to be commonly sensitizing allergenic plants also in the UAE. In most cases, it was not possible to obtain chenopod allergen extracts from locally growing species; therefore, extracts from the same genus had to be used. However, high levels of positive reactions to these commercial chenopod extracts were seen, and patients may have reacted to common allergen epitopes shared by different members of the Chenopodiaceae family.
Many species of Leguminosae, including trees, shrubs, and herbs, grow naturally in the UAE. Several members of this family are also cultivated for animal fodder or ornamental purposes. The prick test panel used included three representatives of this family, and positive reactions to them were common. In addition, prick test reactivity to the mesquite tree was associated with that to acacia and alfalfa, and here again cross-reactivity may play a role. In investigations performed in other Gulf countries, sensitization to legume pollens was likewise common ( 2, 3).
Grasses are important inhalant allergens throughout the world, as in the UAE, where around 100 grass species are represented ( 4), and sensitization to grass pollens has been found to be frequent. Bermuda grass and a 12-grass mixture were selected for the prick test series since the former commonly grows here and the latter should provide a good selection of grass allergens.
I suggest that the basic inhalant allergen series for the inland area of the UAE include the following 15 allergens: cockroach, Dermatophagoides pteronyssinus, D. farinae, cat, Bermuda grass, 12-grass mixture, date palm, mesquite tree, acacia, Russian thistle, lamb's-quarters, scale mix, pigweed mix, mugwort, and plantain. This series could be complemented, when necessary, with animal epithelia or other relevant allergens. It is also desirable that more allergen extracts be available from locally growing plant species.