w20 Nettle

Allergens within Weed Pollens

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  • Latin name: Urtica dioica
  • Family: Urticaceae
  • Common names: Stinging Nettle, American Stinging Nettle, European Stinging Nettle, Hoary Nettle
  • Source material: Pollen
The North American plants cannot be distinguished at the species level from each other or from European plants. The following three subspecies are currently recognised:
  • U. dioica ssp. dioica - European Stinging Nettle
  • U. dioica ssp. gracilis (Ait.) Selander - American Stinging Nettle
  • U. dioica ssp. holosericea (Nutt.) Thorne - Hoary Nettle
A weed species producing pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
The species is distributed throughout Europe, western Asia and North Africa, and has been introduced in western North America, Australia and parts of South America.
 
The Nettle is a fast-growing perennial reaching 1.2 m wide by 1 m tall. In Urticaceae, the plant grows as a large main stem with leaves in opposite pairs. Leaves are produced from March to November. The leaves are large, dark-green, triangular, coarsely toothed, and covered with poison-filled hairs. The leaves discharge their poison when touched, which results in a burning sensation and then a rash.
 
The reddish-brown to greenish-white flowers have no petals, are found in dangling clusters at the junction of stems and leaves, and are dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant). The plant is wind-pollinated. Most Nettle species flower from April to October. The pollination mechanism is unusual: When the sun shines on the curly young flowers, the filaments become taut and eventually shoot up so quickly that the pollen is released in a puff. The small green seeds ripen from June to October.
 
Environment
Nettle is found in open areas and meadows, near buildings, and especially in nitrate-rich soils. Nettle has been used for salads, soups, tea, colouring, as a curdling agent, and in herbal remedies.
 
Allergens
No allergens from this plant have yet been characterised.

Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected, as well as to a certain degree among members of the family Urticaceae, e.g., Parietaria judaica and Parietaria officinalis (1). This however, does not appear to be the general case. RAST inhibition demonstrated the total absence of cross-reactivity between Parietaria and Urtica (2-3). Ramie (Boehmeria nivea), a plant of the Urticaceae family, is widely distributed in the Nagasaki area, and is known as a cause of asthma. Yet Ramie and Parietaria, examined by an ELISA inhibition test using P. officinalis and P. judaica, demonstrated no cross-reactivity (4).

Clinical Experience

IgE mediated reactions
Nettle pollen frequently induces asthma, allergic rhinitis and allergic conjunctivitis (5).
 
Specific IgE to Urtica has also been detected due to occupational sensitisation (6).
 
Urticaceae pollen including both Parietaria and Urtica has been detected in large quantities in aeroallergen studies. It is reported to be the predominant pollen in northwest Spain (7). In Muros, Spain, pollen from this plant comprised 67% of the total aeroallergen load. The proportion of Urticaceae pollen found in Muros was the highest among all samples belonging to the Spanish Aerobiology Network (8). Other studies from Salamanca, Cordoba (9), and other parts of Spain (10- 11) have documented the importance of this aeroallergen in this country.
 
Nettle pollen is also an important aeroallergen in England. Specific IgE to Nettle pollen was found in 13 of 62 patients with a clinical history of summer seasonal respiratory symptoms (12).
 
Nettle pollen has also been detected in aeroallergen studies in Rochester, New York, Minnesota (13), Nebraska (14), and Texas (15), in Balikesir, Turkey (16), and in Korea (17).
 
Other reactions
Stinging Nettle-induced urticaria (18) and contact urticaria (19)  have been reported following non-pollen contact with the Nettle plant. Immediate and delayed hypersensitivity reactions to the Nettle plant may also occur (20).
 
A 57-year-old woman showed symptoms of atropine poisoning after drinking Stinging Nettle tea. Belladonna (Atropa belladonna) was found on investigation to be present in the tea (21). 

Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09 
    2. Bousquet J, Hewitt B, Guerin B, Dhivert H, Michel FB. Allergy in the Mediterranean area. II: Cross-allergenicity among Urticaceae pollens (Parietaria and Urtica). Clin Allergy 1986;16(1):57-64 
    3. Corbi AL, Cortes C, Bousquet J, Basomba A, Cistero A, Garcia-Selles J, d'Amato G, Carreira J. Allergenic cross-reactivity among pollens of Urticaceae. Int Arch Allergy Appl Immunol 1985;77(4):377-83 
    4. Miura N. Ramie (Boehmeria nivea) pollen-induced bronchial asthma and allergenic cross-reactivity of ramie and Parietaria. Arerugi 1993;42(5):649-55 
    5. Wuthrich B, Annen H. [Pollionosis: I. Findings on the clinical aspects and the pollen spectrum in 1565 pollen-sensitive patients. [German] Schweiz Med Wochenschr 1979;109(33):1212-8 
    6. Dutkiewicz J, Skorska C, Milanowski J, Mackiewicz B, Krysinska-Traczyk E, Dutkiewicz E, Matuszyk A, Sitkowska J, Golec M. Response of herb processing workers to work-related airborne allergens. Ann Agric Environ Med 2001;8(2):275-83 
    7. Marcos C, Rodriguez FJ, Luna I, Jato V, Gonzalez R. Pinus pollen aerobiology and clinical sensitization in northwest Spain. Ann Allergy Asthma Immunol 2001 Jul;87(1):39-42 
    8. Vidal C, Dopazo A, Aira MJ. Parietaria pollinosis in an Atlantic area: clinical and palynological data. J Investig Allergol Clin Immunol 2001;11(2):107-11 
    9. Galan C, Alcazar P, Carinanos P, Garcia H, Dominguez-Vilches E. Meteorological factors affecting daily urticaceae pollen counts in southwest Spain. Int J Biometeorol 2000;43(4):191-5 
    10. Hernandez Prieto M, Lorente Toledano F, Romo Cortina A, Davila Gonzalez I, Laffond Yges E, Calvo Bullon A. Pollen calendar of the city of Salamanca (Spain). Aeropalynological analysis for 1981-1982 and 1991-1992. Allergol Immunopathol (Madr) 1998;26(5):209-22 
    11. Gonzalez Minero FJ, Candau P, Tomas C, Morales J. Daily variation patterns of airborne allergenic pollen in southwestern Spain. J Investig Allergol Clin Immunol 1998;8(2):89-93 
    12. Holgate ST, Jackson L, Watson HK, Ganderton MA. Sensitivity to Parietaria pollen in the Southampton area as determined by skin-prick and RAST tests. Clin Allergy 1988;18(6):549-56
    13. Decco ML, Wendland BI, O'Connell EJ. Volumetric assessment of airborne pollen and spore levels in Rochester, Minnesota, 1992 through 1995. Mayo Clin Proc 1998;73(3):225-9 
    14. Bolick MR. Airborne pollen survey for Lincoln, Nebraska. III. Weeds. Nebr Med J 1991 Jun;76(6):178-81 
    15. Lewis WH, Dixit AB, Wedner HJ. Aeropollen of weeds of the western United States Gulf Coast. Ann Allergy 1991;67(1):47-52 
    16. Bicakci A, Akyalcin H. Analysis of airborne pollen fall in Balikesir, Turkey, 1996-1997. Ann Agric Environ Med 2000;7(1):5-10 
    17. Park HS, Jung KS, Jee SY, Hong SH, Kim HY, Nahm DH. Are there any links between Hop Japanese pollen and other weed pollens or food allergens on skin prick tests? Allergy Asthma Proc 2001;22(1):43-6 
    18. Taskila K, Saarinen JV, Harvima IT, Harvima RJ. Histamine and LTC4 in stinging nettle-induced urticaria. Allergy 2000;55(7):680-1 
    19. Oliver F, Amon EU, Breathnach A, Francis DM, Sarathchandra P, Black AK, Greaves MW. Contact urticaria due to the common stinging nettle (Urtica dioica)--histological, ultrastructural and pharmacological studies. Clin Exp Dermatol 1991;16(1):1-7 
    20. Edwards EK Jr, Edwards EK Sr. Immediate and delayed hypersensitivity to the nettle plant. Contact Dermatitis 1992;27(4):264-5 
    21. Scholz H, Kascha S, Zingerle H. Atropine poisoning from "health tea". [German] Fortschr Med 1980;98(39):1525-6

2002