Pollen calendars.

The various pollens are detected successively in the air from January until October. The partial daily or weekly pollen count data can be combined to constitute a summary of the flowering periods of plants with allergenic pol len. A definitive pollen calendar cannot be established, as the dates vary from one year to the next and from one place to another. The date of appear ance of pollen, the date of the pollen peak, its intensity and its duration can be defined. Annual calendars can be used to predict the periods during which a pollen is present in the atmosphere, and therefore to determine th e course of pollen flow during the season. Analysis of pollen counts from y ear to year is useful at several levels: it allows a better diagnosis of se asonal respiratory allergies; it allows the detection of new allergenic pol lens. More adapted treatments can consequently be proposed to patients: sym ptomatic treatments during the pollen season and preventive treatments.