[Outdoor aeroallergens and climate change]

Pollen and fungal spore concentrations in outdoor air are partly dependent on atmospheric conditions. Since the climate is changing, there is a growing body of research on the effects of climate change on aeroallergens. The present article provides a rapid review of this literature, highlighting the points of agreement, but also drawing attention to the main mistakes to be avoided.

For pollen, the prevailing view is that rising temperatures lead to an earlier start to the pollen season, a longer season, increased allergenic potential and higher concentrations. However, there are exceptions: what is true for one taxon, in one place and at one time, can almost never be generalised. For fungal spores, it is even more difficult to state universal rules.

Four priorities can be set for future research: (1) to look for trends only on sufficiently long series and not to neglect possible trend reversals; (2) to give priority to the local scale and the separate consideration of the various pollen and mycological taxa; (3) not to limit oneself to temperature as an element of explanation, but also to consider the other elements of the climate; (4) not to try to explain any evolution in the abundance or seasonality of aeroallergens by climate change alone.

Many more analytical studies giving precedence to observation over reasoning are still required, without any preconceptions, before it is possible to synthesise the impacts of climate change on pollen and, even more so, on fungal spores.