Update on ragweed pollen

Between 1 and 3.5 million people in France are believed to be allergic to ragweed today. What is ragweed? When do pollen levels peak? Is ragweed present across France? Are there ways of keeping it from spreading? Here is our update on the situation. 

What is ragweed?

Ragweed is an invasive plant native to North America. There are several species of ragweed within the genus Ambrosia. The best known and most widespread is common ragweed (Ambrosia artemisiifolia L.). Some other species include giant ragweed (Ambrosia trifida L.), western ragweed (Ambrosia psilostachya DC.) and lacy ragweed (Ambrosia tenuifolia Spreng.).

When do pollen levels peak?

Allergies caused by ragweed pollen occur late in the season, with pollen levels peaking between mid-August and mid-September.  

Where is ragweed found?

Native to North America, ragweed was first identified in Europe in the late 18th century.

Today In France, the main ragweed infestation areas are the Rhône Valley and the Loire Valley. Since 2005, it would seem that ragweed populations have continued to spread increasingly rapidly and become denser in France. The plant is now found in many parts of the country, with varying levels of infestation. There are three main types of infestation areas:

  • areas with heavy infestation/establishment, including the Rhône, Isère, Drôme, Nièvre and Cher départements;
  • "frontline" areas such as the Charentes, Côte-d'Or and Gard départements, located on the edge of the heavily infested areas;
  • areas that are currently affected very little or not at all, such as Brittany.

Although it has been found in Guadeloupe and Martinique, ragweed is not considered invasive in these territories.


How does ragweed spread?

Its spread is favoured by certain human activities: the transport of ragweed-contaminated soil or seeds, agricultural and/or mowing machinery, animal feed, etc.

Common ragweed thrives in:

  • certain agricultural crops such as sunflower or maize, where it causes considerable yield losses;
  • other environments such as riverbanks or roadsides.

What are the health effects of ragweed pollen?

In an expert appraisal published in 2014, ANSES demonstrated that ragweed pollen is among the most problematic in France. This is because it is highly allergenic: it can cause a person to develop a new allergy and can also induce allergy symptoms.

Ragweed pollen causes the same symptoms as other types of pollen in allergic individuals: sneezing, blocked nose, conjunctivitis, redness, swelling of the eyelids, etc. These symptoms heavily impact their quality of life, with consequences in terms of their social and professional life, for example.

Ragweed allergy seems particularly disabling compared with other pollen allergies according to a national survey of healthcare professionals (ANSES, 2020 – ragweed).

In 2020, ANSES estimated that 1,115,000 to 3,504,000 people are allergic to ragweed pollen in metropolitan France.

What is the cost of the health impacts of ragweed?

In 2020, ANSES estimated the costs of the health impact associated with ragweed at a national level:

  • the cost of medical care (e.g. medicines and consultations) may be between €59 million and €186 million each year;
  • the cost of production losses based on absences from work may be between €10 million and €30 million per year.

These costs are expected to increase in the future, due to the predicted expansion of ragweed-infested areas and an increase in pollen levels in ambient air, mainly as a result of climate change.

What steps can be taken to keep it from spreading?


  • In your garden: pull the weeds out before flowering (end of summer) and take care to uproot the entire plant while wearing gloves. Do not do this if you are allergic or sensitive to ragweed.
  • For large amounts of ragweed or for ragweed growing around your property, send a report to:

Building & public works and agricultural sectors:

  • Adopt good ragweed management practices such as cleaning machinery, limiting the amount of bare land, and managing contaminated land.

Local authorities:

  • Act locally in frontline areas (Charentes, Côte-d’Or, Gard) and in areas that still have low levels of ragweed by implementing, starting today, specific (prefectural order) and coordinated regulations by appointing a ragweed expert responsible for control measures on the ground.

ANSES's work on biological air contaminants

For several years now, ANSES has been studying biological contaminants (pollen, mould, etc.) found in air to assess their health impacts on exposed populations. This includes the following work: