The pollen, which is described as the "kind that causes hayfever" (known as "rhume des foins" in French) is spreading, according to reports.
A "red alert" means the risk of allergies is very high, at a four out of five on the scale, created by air pollution group L’Association pour la Prévention de la Pollution Atmosphérique (APPA).
Every year, grass pollen especially causes some people to have significant hayfever, including a runny nose, itchy or weeping eyes, a headache, and repeated sneezing.
People who suffer from allergies can take some simple actions to reduce the impact.
One tip from APPA is to rinse your hair with clean water before going to bed, which will remove any pollen that could be lingering.
It also advises people to wear sunglasses when leaving the house, to limit the amount of pollen that could irritate your eyes.
The guidelines also advise against drying washed clothes outside, as this can cause the fabric to collect pollen, which in turn can become an irritant when the clothes are later worn.
Every week during the summer, APPA releases a "pollen forecast" to warn people who are affected by the fluctuating levels.
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