Impact of pollen on human health: more than allergen carriers?

The transfer of pollen from floral anther to recipient stigma is the critical reproductive event among higher plants--this is the botanical view of pollen. Proteins and glycoproteins from pollen can function as allergens, environmental molecules interacting with the human immune system to elicit an allergic response in susceptible individuals--this is how allergists and immunologists see pollen grains. Between 10 and 25% of the population now have symptoms of hay fever or allergic asthma and the incidence has more than doubled in the past three decades while the reason(s) for this increment are only hypothetical, but there is a multitude of them. Despite our natural focus on this impact of pollen on human health, pollen have to be considered in a larger context. First of all, to evaluate the bioavailability of allergens from pollen, we have to understand their function and their influence factors. Furthermore, pollen grains are not only releasing proteins eliciting specific immune responses, but they also liberate bioactive lipid mediators and this much more rapidly. And last but not least, recent observations indicate, that pollen do not only induce allergy and thus have a much broader impact on human health. This review is an attempt to favour this holistic view of pollen and their impact on human health.