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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.

There is growing evidence to support an increase in air temperature over recent decades, with significant effects on aeroallergens such as pollen. It is generally accepted that the trend will continue, and become even more pronounced in the future.Global climate change is already affecting, and will continue to affect, with earlier floral initiation, the timing of the production of allergenic pollen. In addition, a warmer climate might lead to a longer pollen season and more days with high pollen counts. It could also increase the allergen content of pollens, and result in extension of plant species towards the poles and higher altitudes. Finally, rising levels of atmospheric CO₂ are likely to reinforce these trends.These predictions are subject to uncertainties that may lead to outcomes that differ materially from what is expected. Understanding the magnitude and direction of the changes affecting pollinisation is critical in order to quantify the future allergic disease burden and model the impacts of different climate change scenarios.Climate change influences the production, distribution, dispersion and allergenicity of anemophilous pollen and the growth and distribution of weeds, grasses and trees that produce it. These changes in aeroallergens and subsequent human exposure could affect the prevalence and severity of allergic disorders. There is, therefore, an important public health issue that requires development and implementation of appropriate response strategies without delay.

Pollen is a major cause of allergy and monitoring pollen in the air is relevant for diagnosis, treatment and prevention, as well as for biomedical and biological research. Many aero-biological studies have been conducted all over the world to ascertain aerial concentrations and seasonality of pollen grains.Monitoring of airborne biological particles is carried out by various gravimetric, impaction, and suction sampling devices. The Hirst trap, later modified to Burkard(®) or Lanzoni(®) traps, is the most widely used sampler. Counting and identifying pollen grains is then performed under optical microscopy. Based on differences in airborne pollen recorded over several years of observation, pollen calendars have been drawn up as aids to allergy diagnosis and management but they could be replaced advantageously by allergy-risk calendars. Pollen counts also provide valuable information about the geographical origin of pollen grains.Since the identifying and counting of pollen grains in ambient air samples is still a demanding and time-consuming task, there is an increasing interest in the automation of pollen monitoring. Furthermore, the divergence sometimes observed between clinical observations and pollen counts provides an incentive to collect aero-allergens directly. Lastly, pollen monitoring could be improved through the use of personal bioaerosol samplers.Great progress has been made in aerobiology for over a century, but much remains to be accomplished, particularly in relation with the standardization of methods.

The purpose of this paper was to verify the effect of pollen peaks on blood eosinophilia in an all and sundry population, including allergic as well as non-allergic subjects, so that we can open up new horizons in the understanding and prevention of pollinosis. Daily eosinophilia counts of hospital patients were measured at the time of a blood checkup (1996-1998), and divided into six classes. Those data were compared to daily pollen counts of twelve taxa, coming from the Hirst trap of Dijon (France). An eosinophilia increase occurred when hazel, hornebeam, birch, oak, grasses, ragweed and plantain were present in high concentration. In other cases, only simultaneous presence of several taxa seemed to play a part, because of cross-reactivity or polysensitization. Lastly, Cupressaceae-Taxaceae and ragweed were seen as increasing eosinophilia in seemingly non allergic people. The analysis of eosinophilia in the general population was able to reveal potential allergic patients and potential allergic diseases.

Over a 28-year period cerebrospinal meningitis, in sporadic as well as epidemic situations, mainly affected the Beninese territory from November to March, April or sometimes May. On the average, the acme occurred in February-March. A regression analysis confirmed that 14 to 34.5% of the temporal variability of the disease was due to the northern trade wind (harmattan) and a low absolute humidity in the northern areas, which constitute the main epidemiological pole of the country. On the contrary, cerebrospinal meningitis and climate turned out to be fully independent one from the other in the southernmost areas, where the harmattan is seldom experienced although the meningitis belt is at the present time spreading southwards. But the case-fatality ratio was especially high in the coastal region and during the off season, i.e. when endemic meningitis predominantly affected small children aged under one year. In any way, the climate-meningitis relationship proved to be weaker than is sometimes assumed, perhaps because this relationship is partly overshadowed by both anthropic effects (vaccination campaigns) and latency before disease outbreak.