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Pollen asthma

During the days with very high airborne pollen concentrations some pollinosis sufferers may also have symptoms of the lower respiratory tract or asthmatic attack of various severity. The nose filters the pollen grains. Mechanically, it does this by means of its internal structure, creating turbulence in the nasal air flow. As a result, particles of over 10μ in diameter-including pollen-are retained and the allergen carrying pollen grains are caught in the nasal mucus. During recent years, aerobiological and immunochemical research has shown that pollen allergenic activity is carried through the air not only by pollen grains, but also for a substantial fraction by the paucimicronic and submicron atmospheric aerosol fraction. Particles of  5μ or less penetrate the small airways. These small particles, which are abundantly present in the air, can penetrate deeply into the respiratory tract. Although only a fraction will be deposited there, they might introduce sufficient allergen to cause symptoms of pollen asthma.[1]

Pollinosis is defined as the appearance of respiratory symptoms (rhinoconjunctivitis and/or asthma) as a result of the inhalation of pollen to which the individual is sensitized. Pollen allergy becomes all the more relevant on taking into account that it may be responsible for the development of plant food allergy, or may even constitute the direct cause of esophageal, gastric and/or intestinal inflammation in the context of a digestive allergic process. Pollen can act as a source of allergens that induce primary sensitization in the host as a result of inhalation, with secondary allergy to plant foods containing shared allergens via a cross-reactivity mechanism. The observed pattern of plant food allergy depends on the dietary habits of the population in a given geographical setting, and on the pollination found in that setting. Pollinosis may account for the greater or lesser prevalence of allergy to certain plant foods, and for the severity of the associated reactions. Beyond the digestive tract inflammation that may result from allergy to a given food, pollinosis is also intrinsically able to generate a clinically relevant or irrelevant Th2-mediated inflammatory response at digestive level, and may even give rise to eosinophilic esophagitis. Inter-relation with the airway may also extend to the digestive tract as a consequence of the systemic response that characterizes allergic disease[2].

1. Merrel Dow: Pollen in close-up. Franklin Scientific Projects. 1989. p. 15.

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2. Bartra J, Sastre J, del Cuvillo A, Montoro J, Jáuregui I, Dávila I, Ferrer M, Mullol J, Valero A. From pollinosis to digestive allergy. J Investig Allergol Clin Immunol. 2009;19 Suppl 1:3-10.