Many people suffer or are at risk of suffering allergies. Many of these problems are caused by the pollen released into the air by thousands of plants in the environment. These are examples of pollinosis or allergic rhinitis produced by pollen.Pollen grains are minute and invisible to the human eye. After release from the producing plant, they are transported in air (dispersion) and can travel considerable distances. When the atmospheric concentration of certain pollen species reaches a certain level, exposed people who are allergic to these species will develop the typical manifestation of the allergic reaction.

It is important to stress the importance of different meteorological factors, since the atmospheric conditions influence pollen concentrations in the air. In this sense, dry and warm conditions or the presence of moderate winds that favour pollen dispersion tend to facilitate the appearance of pollinosis. In contrast, rain tends to clear pollen from the air—thereby reducing the risk of allergic episodes.

Although we cannot avoid coming into contact with pollen, it is possible to palliate its deleterious effects by adopting a series of measures such as avoiding the countryside in the peak pollen season, traveling with the windows closed, visiting the seaside on holidays and closing the windows at home in the afternoon-evenings (when pollen concentration in the air peaks). Smoking should also be avoided and, where necessary, susceptible people should wear a surgical mask when they go outside.

Thanks to the distribution of pollen traps throughout the country, it has been possible to develop a "pollen calendar" with precise information on when pollens appear, how long they remain present, when they reach peak concentrations, when the concentrations begin to decrease, when they disappear, etc.

Although there is a generalised belief that pollen grains are well differentiated by their morphological characteristics (appearance, size, shape, ornamentation / details, etc.), experts know the difficulties involved in specific identification because different species often present similar pollinic morphologies.