t214 Date

Allergens within Tree Pollens

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  • Latin name: Phoenix canariensis
  • Family: Arecaceae
  • Common names: Canary Island Date Palm tree
  • Source material: Pollen
Not to be confused with the "true" Date Palm tree (Phoenix dactylifera) which is cultivated for its fruit.
  • Canary Island Date Palm (P. canariensis)
  • Date Palm (P. dactylifera)
  • Sugar Date Palm (P. sylvestris)
  • Blue Date Palm (P. zeylanica)
  • Pygmy Date Palm (P. roebelenii)
See also: Date (the fruit of Phoenix dactylifera) Rt289
 
A tree species producing pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
Phoenix canariensis is native to the Canary Islands in the Atlantic Ocean off northeast Africa. These Palms are popular landscape items around the world, and particularly along coastal regions.
 
Although there are many Palms that we call "Date Palms" (i.e., Pygmy Date Palm, Senegal Date Palm, Canary Island Date Palm, etc.), Phoenix dactylifera is the "true" Date Palm from which the tasty fruit is obtained.
 
The Canary Island Date Palm is a very large and imposing tree. It grows up to 20m tall. The large trunk supports a huge crown of over 50 arching, pinnate leaves that may reach 6 meters long. The leaves are deep green, shading to a yellow stem where the leaflets are succeeded by vicious spines. The trunk is covered with diamond designs that mark the point 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 to yellow flowers are borne on stalks about 2m long in summer. 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 shade and approximately 2 cm in size. They are edible but not very tasty.
 
Environment
These Palms are popular in near frost-free climates around the world, and particularly along coastal regions.
 
Allergens
Date pollen from the related species Phoenix dactylifera has six major allergens;
  • 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)
  • Pho d 6 (a 37-40 kDa protein)
The 12, 14.4, 57, and 65-67 kDa bands bind 80-93%, and the 28-30 and 37-40 kDa bands 60-80% of atopic sera (1).

Due to close relation within the same genus, Phoenix canariensis could be expected to contain similar allergens.

Potential Cross-Reactivity

Extensive cross-reactivity among the different individual species of the genus could be expected (2). 
 
RAST inhibition studies have demonstrated significant cross-reactivity between P. canariensis pollen and P. dactylifera pollen (3).
 
A study from Calcutta, India, found cross-reactivity between the pollen of 4 species of important Palms in that region (Areca catechu, Cocos nucifera, Phoenix sylvestris and Borassus flabellifer) (4). This would indicate that, as cross-reactivity between P. canariensis, P. dactylifera and P. sylvestris is likely, cross-reactivity between P. canariensis and Areca catechu, etc., may also be possible. On average, 30-50% of the patients showed positive skin reactions and enhanced specific IgE level to more than one Palm pollen extract. Further evidence of allergenic crossreactivity among the four Palm pollen grains was demonstrated by dot blotting and ELISA inhibition studies (5).

Antigens and allergens of date fruits cross-react with date pollen allergens and date fruit-sensitive as well as date pollen-allergic patients' sera recognize the same group of date fruit IgE-binding components (1).

Clinical Experience

IgE mediated reactions
Asthma, allergic rhinitis, allergic conjunctivitis and contact urticaria can occur following contact with pollen from this tree (3).
 
The skin prick test (SPT) and measurement of specific IgE are useful in the diagnosis of this allergy (3).
 
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 the pollen 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 this pollen. Pollen levels decreased with increasing distance from the trees, and were low at approximately 100 m from a source (6). 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.

Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Kwaasi AA, Parhar RS, Tipirneni P, Harfi H, 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(7):511-518  
    2. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09   
    3. Blanco C, Carrillo T, Quiralte J, Pascual C, Martin Esteban M, Castillo R. Occupational rhinoconjunctivitis and bronchial asthma due to Phoenix canariensis pollen allergy. Allergy 1995;50(3):277-80   
    4. 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):977-983   
    5. 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):281-290   
    6. 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):305-310

2002



Further Reading