Retrospective and predictive systems of information on airborne pollen concentrations in relation to hay fever

Summary In this survey, the most important aspects concerning information on airborne pollen concentrations in relation to hay fever are reported. Six of these aspects are briefly discussed. They are: target group, “spectivity”, subject exactness, routes, frequency. These aspects of information system can concern airborne pollen and/or pollinosis. The “Leiden” system has two flows of information: daily hay-fever forecast and weekly pollen bulletin.