Hayfever victims on alert for ragweed pollen season

In Greek mythology it is the food of the gods that helped keep them immortal but, here on earth, ambroisie as it is known in France - aka common ragweed - is an invasive plant that brings misery to hayfever sufferers in the autumn.

In France, it is most common in the Rhone Valley, the Nièvre, and the Dauphiné - but it has spread to other areas of the country, and is found on roadsides, construction sites, in fields or on river banks. Experts predict it will be common to all parts of the country by 2050.

It flowers - and therefore pollinates - in August and September, extending the allergy season for hayfever sufferers.

It may look harmless but its pollen triggers symptoms in anyone sensitive to allergies: asthma, itchy palate or eyes, coughs, sore throat or rhinitis.

Health experts are so concerned that pulling up the weed - the only effective way to stop it pollinating - can be ordered by prefectoral decree, putting the onus on property owners to keep their land clear before it flowers.

"The plant pollinates early in the morning, usually between 7am and 11am. So the easiest thing is to avoid going out at these times, ventilating your home, or hanging your laundry outside," said Gilles Oliver, of the le réseau national de surveillance aérobiologique (RNSA).

An estimated 13% of the population is allergic to the pollen.