Date
Summary
Not to be confused with the ‘true’ date palm tree (Phoenix dactylifera), which is cultivated for its fruit
Route Of Exposure
Other Topics
Phoenix canariensis is native to the Canary Islands in the Atlantic Ocean off north-east Africa. These palms are popular landscape items around the world, particularly in coastal regions with Mediterranean climates.
Although there are many palms that we call ‘date palms’ (e.g. Canary Island date palm, pygmy date palm, Senegal date palm), Phoenix dactylifera is the true date palm, cultivated for its delicious fruit.
The Canary Island date palm is a very large and imposing tree. It grows up to 20 m tall. The large trunk supports a huge crown of over 50 arching, pinnate leaves that may each measure 6 m long. The leaves are deep green, shading to yellow stems where the leaflets are succeeded by vicious spines. The trunk is covered with diamond designs that mark the points of attachment of previously discarded leaves.
Palms have separate male and female plants. Flowers are mostly wind- pollinated, and the plant produces a large amount of pollen. Cream-coloured to yellow flowers are borne in summer on stalks about 2 m long. The heavy bunches of fruits (dates) are yellow-orange or deep red, with edible, sweet but almost dry flesh. They are cylindrical to ellipsoid in shape and approximately 2 cm in size. They are edible but not very palatable.
These palms occur in nearly frost-free climates around the world, and particularly in coastal regions.
Clinical Relevance
IgE mediated reactions
Asthma, allergic rhinitis, allergic conjunctivitis and contact urticaria may occur following contact with pollen from this tree.
An individual was described with asthma, rhinoconjunctivitis, and contact urticaria from pruning dried leaves from this palm. A skin-prick test and IgE antibody tests were positive. A bronchial provocation test with the pollen elicited a positive response.
In an Israeli study, pollen extracts of 12 varieties of palm and 9 of pecan were tested on 705 allergic patients living in 3 cities and 19 rural settlements. Sensitivity to extracts of date palm pollen and pecan tree pollen was much higher among residents of rural than of urban communities. There was a relationship between the abundance of these trees in a region and the incidence of positive skin-prick tests to their pollen. Pollen levels decreased with increasing distance from the trees, and were low at approximately 100 m from a source. In view of the significant cross-reactivity between members of this species, the findings of this study would be relevant to areas where P. canariensis is grown.
In 553 asthmatics in Kuwait, sensitisation to common aeroallergens evaluated by serum-specific IgE testing found that 87% were sensitised to pollens, 76% to house dust and 30% to moulds. The three most prevalent sensitising pollens were from saltwort (Salsola kali) (71%), Bermuda grass (63%), and mesquite tree (Prosopis juliflora) (63%), all of which are horticultural plants imported for the purpose of ‘greening’ the desert. Forty per cent were sensitised to date palm tree.
In a study from West Bengal, India, it was reported that 18 common airborne types of pollen were detected, and that they induced sensitisation in susceptible individuals: the closely related species P sylvestris (sugar date palm) was shown to result in sensitisation in 43% of 475 individuals tested.
Cross-Reactivity
Extensive cross-reactivity between the different individual species of the genus could be expected.
RAST inhibition studies have demonstrated significant cross-reactivity between P. canariensis pollen and P. dactylifera pollen. Furthermore, allergens present in the fruit of P. dactylifera have been reported to be cross-reactive with pollen allergens from the same palm, and the study reported that date fruit-sensitive as well as date pollen-allergic patients’ sera recognised the same group of date fruit IgE-binding components.
Studies from India have reported cross-reactivity bettween the pollen of 4 species of important palms in that region (Areca catechu, Cocos nucifera, Phoenix sylvestris and Borassus flabellifer), suggesting cross-reactivity between these 4 palms and the closely-related date tree. Cross-reactivity between the 4 Palm pollen grains was also demonstrated by dot blotting and ELISA inhibition studies.
The closely-related P. dactylifera contains a profilin allergen, Pho d 2, which was shown to have high sequence identity with other allergenic food and pollen profilins. Pollen from this palm has been reported to show cross-reactivity with antigens from Artemisia, Cultivated rye (Secale cereale), Timothy grass (Phleum pratense), Sydney golden wattle (Acacia longifolia) and Bermuda grass (Cynodon dactylon) pollen. Cross-reactivity was also reported to exist between pollen from this palm and a number of foods implicated in oral allergy syndrome, but the authors stated that the clinical relevance of this needed to be elucidated.
References
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- Waisel Y, Keynan N, Gil T, Tayar D, Bezerano A, Goldberg A, et al. Allergic responses to Date Palm and pecan pollen in Israel. [Hebrew] Harefuah 1994;126(6):305-10.
- Ezeamuzie CI, Thomson MS, Al-Ali S, Dowaisan A, Khan M, Hijazi Z. Asthma in the desert: spectrum of the sensitizing aeroallergens. Allergy 2000;55(2):157-62.
- Boral D, Chatterjee S, Bhattacharya K. The occurrence and allergising potential of airborne pollen in West Bengal, India. Ann Agric Environ Med 2004;11(1):45-52.
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- Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
- Chowdhury I, Chakraborty P, Gupta-Bhattacharya S, Chanda S. Allergenic relationship among four common and dominant airborne Palm pollen grains from Eastern India. Clin Exp Allergy 1998;28(8):977-83.
- Singh AB, Kumar P. Aeroallergens in clinical practice of allergy in India. An overview. Ann Agric Environ Med 2003;10(2):131-6.
- Kwaasi AA, Parhar RS, Tipirneni P, Harfi HA, al-Sedairy ST. Cultivar-specific epitopes in Date Palm (Phoenix dactylifera L.) pollenosis. Differential antigenic and allergenic properties of pollen from ten cultivars. Int Arch Allergy Immunol 1994;104(3):281-90.
- Asturias JA, Ibarrola I, Fernandez J, Arilla MC, Gonzalez-Rioja R, Martinez A. Pho d 2, a major allergen from date palm pollen, is a profilin: cloning, sequencing, and immunoglobulin E cross-reactivity with other profilins. Clin Exp Allergy 2005;35(3):374-81.
- Kwaasi AA, Harfi HA, Parhar RS, Saleh S, Collison KS, Panzani RC, Al-Sedairy ST, Al-Mohanna FA. Cross-reactivities between date palm (Phoenix dactylifera L.) polypeptides and foods implicated in the oral allergy syndrome. Allergy 2002;57(6):508-18.