Pine
Summary
Pine trees (Pinus spp.) are distributed widely in the Northern hemisphere, both naturally and as part of commercial forestry. Although pine pollen was thought to have low allergenic potential, it is now an inhaled allergen of growing concern. Pine pollen causes allergic rhinitis, conjunctivitis and asthma in adults and children. Lung function deficits and reduced performance of the bronchial epithelial barrier are reported in clinical literature. There is a high level of cross-reactivity between Pinus species. Cross-reactivity to Cypress, Olive and Perennial Ryegrass allergens has been found in some studies.
Epidemiology
Worldwide distribution
Pine pollen was long considered to be non-allergenic. However, sensitization to conifer tree pollen (Cupressaceae and Pinaceae) is thought to have increased dramatically in recent years; in a Spanish study of conifer pollen allergy, 11 of 499 allergic patients (2.2%) showed a positive skin prick test to Pinus pinea. Among 48 patients with suspected pollen allergy, 12% were sensitized to Pinus radiata; this may be primary sensitization to or allergic sensitization to other pines or cross-reactive species.
Pediatric issues
Aeroallergen sensitization to P. radiata was found in 7.5% of 371 skin-prick tests in pediatric patients studied over 5 years in Cova da Beira, Portugal.
The prevalence of ambient Pinus pollen on the day before and 3 days before assessment was associated with reduced lung function (when measured by forced expiratory volume in the first second [FEV1] and forced vital capacity [FVC]) in a cohort of 8-year-old Australian children.
Route Of Exposure
Main
The main route of exposure is inhalation. The relatively large size of Pinus pollen may limit its exposure to the larger airways (trachea and bronchi); however, pollen grains can rupture into fragments small enough to penetrate the lower airways.
Clinical Relevance
Pine pollen is associated with allergic rhinitis, conjunctivitis and increasingly with asthma. It was previously considered of low allergological relevance. Regional sensitization has been recorded in excess of 8%, so its clinical relevance is likely to be underestimated. Pine pollen is considered a plant allergen of emerging importance. Bacteria, endotoxins and molds found on Pinus pollen may contribute to respiratory symptoms in sensitized individuals.
Pinus pollen exposure is associated with decreased lung function test measurements (forced expiratory volume and forced vital capacity). Components of P. sylvestris pollen reduce bronchial epithelial barrier functionality, via increased trans-epithelial electrical resistance and polarized release of inflammatory mediators by epithelial cells.
Diagnostics
Pine pollen is sampled using a vacuum air sampler such as the Burkard spore trap or a large flow pollen collector and extracted using hydrofluoric acid or ammonium bicarbonate.
Prevention And Therapy
Allergen immunotherapy
Due to the high number of allergic patients mono-sensitized to pine pollen, specific immunotherapy may be useful.
Avoidance
Avoidance may be impossible during the pollen season, due to the high prevalence of Pinus species throughout the Northern hemisphere and their global spread. Studies of pollen prevalence in Slovakia and South Korea found Pinus spp. to be the predominant tree pollen.
Cross-Reactivity
Most patients are mono-sensitized to pine pollen, with a high level of cross-reactivity between Pinus species.
Cross-reactivity between pine and cypress (Cupressaceae) pollen is reported as present and absent. Cross-reaction between Monterey pine (P. radiata) and olive tree pollens (Olea europaea) has been identified in Germany. Correlation between sensitivity scores for pine pollen and grass pollen has been reported, although a previous study found this only in patients also sensitized to perennial ryegrass.
References
- Bishan C, Bing L, Chixin C, Junxia S, Shulin Z, Cailang L, et al. Relationship between airborne pollen assemblages and major meteorological parameters in Zhanjiang, South China. PLOS ONE. 2020;15(10):e0240160.
- So HJ, Moon SJ, Hwang SY, Kim JH, Jang HJ, Jo JH, et al. Characteristics of airborne pollen in Incheon and Seoul (2015-2016). Asia Pac Allergy. 2017;7(3):138-47.
- Fernández-González M, Lara B, González-Fernández E, Rojo J, Pérez-Badia R, Rodríguez-Rajo FJ. Pinus Pollen Emission Patterns in Different Bioclimatic Areas of the Iberian Peninsula. Forests. 2021;12(6).
- Lambert KA, Katelaris C, Burton P, Cowie C, Lodge C, Garden FL, et al. Tree pollen exposure is associated with reduced lung function in children. Clin Exp Allergy. 2020;50(10):1176-83.
- Shevtsova T, Kacaniova M, Petrová J, Brindza J, Garkava K. Microbiota of pinus pollen as adjuvant factor of allergy. Journal of Microbiology, Biotechnology and Food Sciences. 2016;05:627-32.
- Röseler STM, Baron JM, Höflich C, Merk HF, Bas M, Bier H, et al. "New" inhalant plant allergens. Allergol Select. 2020;4:1-10.
- CABI. Pinus (pines) Wallingford, UK: CABI Internatioonal; 2021 [cited 2021 02.11.21]. Available from: https://www.cabi.org/isc/datasheet/41522.
- Gastaminza G, Lombardero M, Bernaola G, Antepara I, Muñoz D, Gamboa PM, et al. Allergenicity and cross-reactivity of pine pollen. Clin Exp Allergy. 2009;39(9):1438-46.
- Domínguez-Ortega J, López-Matas M, Alonso MD, Feliú A, Ruiz-Hornillos J, González E, et al. Prevalence of allergic sensitization to conifer pollen in a high cypress exposure area. Allergy Rhinol (Providence). 2016;7(4):200-6.
- Loureiro G, Rabaça MA, Blanco B, Andrade S, Chieira C, Pereira C. Aeroallergens sensitization in an allergic paediatric population of Cova da Beira, Portugal. Allergol Immunopathol (Madr). 2005;33(4):192-8.
- Blume C, Swindle EJ, Gilles S, Traidl-Hoffmann C, Davies DE. Low molecular weight components of pollen alter bronchial epithelial barrier functions. Tissue Barriers. 2015;3(3):e1062316.
- Ščevková J, Dušička J, Hrubiško M, Mičieta K. Influence of airborne pollen counts and length of pollen season of selected allergenic plants on the concentration of sIgE antibodies on the population of Bratislava, Slovakia. Ann Agric Environ Med. 2015;22(3):451-5.
- Asam C, Hofer H, Wolf M, Aglas L, Wallner M. Tree pollen allergens-an update from a molecular perspective. Allergy. 2015;70(10):1201-11.
- Katotomichelakis M, Danielides G, Iliou T, Anastassopoulos G, Nikolaidis C, Kirodymos E, et al. Allergic sensitization prevalence in a children and adolescent population of northeastern Greece region. Int J Pediatr Otorhinolaryngol. 2016;89:33-7.