"At the moment it is the willow and the hazel that emit the most. In two weeks we will have the grasses with the foxtail and the fragrant blur", observes Hervé Tiger, gardener-botanist of the city of Rennes.

In front of it, large planters bathed in sunlight are home to ryegrass, timothy, woolly grass, orchardgrass, bulbous wheaten, fragrant fluff, as well as birches, oaks, hazel trees, willows.

Each plant was taken from the wild, within a radius of 20 kilometers around Rennes, at the four cardinal points.

"The idea is to have a greater genetic variability because each plant does not emit pollen at the same time", explains to AFP the botanist, finger pointing on the stamens, pollen bags.

"If we shake a little, we see the very yellow pollen grains, in the form of very fine dust. That's what is allergenic," he continues.

Male fertilizing element of the flower, the pollen lands on the pistil of a female flower of the same species to fertilize it and form the fruit.

It is made up of tiny grains a few tens of micrometers in diameter, the finest and lightest, transported by the wind, being the most likely to reach the respiratory tract and cause allergies.

Every morning, Hervé Tiger reviews the flowering of the selected species with allergist doctors.

"The objective is to visually observe the pollen emissions. We look to see if there are stamens and we note in a small notebook the date of the start and end of the emission, the most important thing being to observe the whole first issue to raise the alarm," he said.

Botanist Hervé Tiger notes his observations after studying stamens in the Rennes pollinarium, March 18, 2022 Damien MEYER AFP

"Prevention Tool"

The information is then validated by an allergist doctor, entered into a centralized database in Nantes (https://www.alertepollens.org/) and disseminated to the population.

In Rennes, 1,300 patients and doctors appear in the database, registration being free.

"Each zone has its alerts, because allergenic plants are not necessarily the same everywhere", specifies the gardener.

There are twenty pollinariums in France, four of which are in the process of being opened.

The first began to operate in Nantes in 2012. It was the allergists who came up with this "sentinel" tool, believing that there was too great a difference between the symptoms noted in their patients (rhinitis, asthma, conjunctivitis, etc.) and the pollens detected by atmospheric sensors in towns, which are less sensitive at the very start of emission.

“It is a very interesting prevention tool from a public health point of view”, assures Mickaël Pouliquen, allergist doctor and referent of the Rennes pollinarium.

"Thanks to it, you know very precisely when to take and when to stop your antihistamine medication. This also makes it possible to identify the pollen at the origin of a respiratory allergy", he continues.

In addition, treatment administered from the first gram of pollen in the air is "more effective than treatment in the midst of an allergic crisis", adds the doctor.

He underlines "the increase in the prevalence of allergies for 30 years, the WHO even predicting that one in two people will be allergic in 2050".

In France, 10 to 20% of the population suffers from pollen allergy.

Hazelnut stamens, in the Rennes pollinarium, March 18, 2022 Damien MEYER AFP

Ultimately, the objective is to crisscross the entire territory of pollinariums with a hundred structures.

"Global warming and pollution contribute to increasing the amount of pollen in the air", recalls Julia Maguéro, in charge of partnerships at the Association des pollinariums sentinels de France (APSF).

In fact, the heat lengthens the duration of the pollen seasons.

“People are more and more affected throughout the year whereas before they were from February to September”, she specifies, adding that “pollution also increases the allergenic potential of pollens, leading to more and more respiratory problems.

© 2022 AFP