t214 Date

Not to be confused with the ‘true’ date palm tree (Phoenix dactylifera), which is cultivated for its fruit f289

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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.

IgE mediated reactions

Asthma, allergic rhinitis, allergic conjunctivitis and contact urticaria may occur following contact with pollen from this tree. (1)

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. (1)

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. (2) 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. (3)

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. (4)

To date no allergens have been isolated from this plant.

Six major allergens have been isolated from date pollen from the related species P. dactylifera: Pho d 1 (a 12 kDa protein), Pho d 2 (a 14.4 kDa protein), Pho d 3 (a 57 kDa protein), Pho d 4 (a 65-67 kDa protein), Pho d 5 (a 28-30 kDa protein), and Pho d 6 (a 37-40 kDa protein). The 12, 14.4, 57, and 65-67 kDa bands bind 80-93% of atopic sera, and the 28-30 and 37-40 kDa bands 60-80%. (5) Due to its close relationship within the same genus, P. canariensis could be expected to contain similar allergens.

A more recent study reported that 60 patients (30%) were skin test-positive to date palm profilin, Pho d 2, of the closely-related species P. dactylifera. (6)

Cross Reactivity

Extensive cross-reactivity between the different individual species of the genus could be expected. (7)

RAST inhibition studies have demonstrated significant cross-reactivity between P. canariensis pollen and P. dactylifera pollen. (4) 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. (5)

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), (8,9 )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. (10)

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. (11) 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. (12)

Last reviewed: May 2022