Blistered children’s hands, dog paws covered with blisters… These images, accompanied by a photo of a plant, may seem alarmist. On closer inspection, the plant species featured in several very viral Facebook posts over the past few days is familiar. This is the “giant hogweed”. Very present in France, especially along the roads, it has been listed since 2017 on the list of invasive species of concern of the European Union. According to the authors of these publications, this plant would also cause severe burns.
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The plant in question is a Heracleum mantegazzianum, more commonly known as “giant hogweed”. This is a species of herbaceous plants of the family Apiaceae. As the viral publications point out, this plant is indeed harmful to humans as well as to animals. Its sap is irritating to the skin. Worse, it contains furocoumarins, a substance sensitive to light. Exposed to the sun, it can cause lesions and burns, which result in red patches or blisters like those shown in the photos accompanying certain publications. This is what scientists call phototoxicity.
The Fernand-Widal Poison Control Center in Paris is familiar with this plant and compares its effects to latex from fig trees and to Corsican peucedan. “These furocoumarins, photosensitive toxic agents, are unfortunately” classics “,” explains a doctor from the center in 20 minutes. One of the difficulties is that the effect is not immediate, it is often necessary to wait for exposure to the sun and the burn to realize that you have been “touched”.
However, those who realize that they have handled this plant can first soak up the sap with an absorbent paper or cloth without rubbing. After that, one should wash the area with soap and water and then rinse thoroughly before covering the area to protect it from the sun for two to three days.
According to the National Botanical Conservatory of Brest, giant hogweed was introduced to Western Europe in the 19th century as an ornamental plant, before actually becoming invasive at the end of the 20th century. Very competitive species which, “by its rapid growth and its large size, eliminates most of the native species where it establishes itself”, it is recognizable by its large size (from 2 to 3 meters). Its leaves are divided into one to three deeply indented and toothed leaflets. They are often over a meter long, reaching three meters in length (with the petiole) and 1.5 m in width.