The images were pretty shocking.

A mother and her daughter suffered painful blistering hours after paddling in a lake near the town of Aix-les-Bains in the Savoie département, south-east France, Le Dauphiné Libéré reported.

Depuis une semaine, une Aixoise et sa fille souffrent de cette maladie mystérieuse, apparue un peu plus de 24 heures après une promenade sur la plage du Rowing à Aix-les-Bains. https://t.co/mQ1pv5GPt1

— Le Dauphiné Libéré (@ledauphine) June 18, 2024

The following day, they both suffered intense burning, stinging sensations on their legs, and then the blisters appeared, French media reported.

They were initially prescribed corticosteroid cream and allergy medication, but a dermatologist diagnosed phytophotodermatitis – a rash occurring after contact between the skin and certain chemicals found in many plants.

It’s sometimes known in France as dermite des prés (meadow dermatitis), and develops when the chemicals in the plant come into contact with skin and are exposed to sunlight. The painful condition is treatable, and – in this instance – both mother and daughter are responding well to the care they are receiving, reports say.

The regional health authority in Auvergne-Rhône-Alpes told BFM TV that it had received no reports of phytophotodermatitis or similar cases.

READ MORE: MAP: How to check the quality of the bathing water in France’s seas and lakes

So should I avoid swimming or paddling in French makes?

Such a reaction is, however, extremely rare and bathing is considered risk-free in supervised areas, where the water complies with regulatory standards. 

But it’s a good idea to acquaint yourself with local rules before taking a ‘wild’ dip – and keep up to date with any temporary changes in water quality. During the bathing season, the local health authorities inspect all bathing areas, and post results of water analysis near beaches and bathing areas.

The French Health Ministry regularly updates an interactive map of safe swimming locations, based on the data of each regional health agency, noting spots that are inspected at least once per month by the local authorities. 

The site allows users to select their département of choice and then zoom in on the beaches or river spots of interest.  Swimming areas are then ranked in a series of colours from excellent (blue) all the way through to pink, where swimming is prohibited for public health reasons. 

Even where swimming is considered safe, water quality is changeable. Recent heavy rains, for example, could cause overflowing from collection or treatment facilities intended for wastewater or significant surface runoff. 

Household wastewater, animal excrement and livestock effluents discharged into the environment, polluting bathing sites, can lead to poor water quality. 

Meanwhile, in artificial water bodies, dermatitis-causing parasites – carried by water fowl – can develop when the water temperature is high enough (from 25°C). These can lead to itching, sometimes known as dermatite des nageurs, or la puce du canard (swimmer’s dermatitis or duck itch).

In both saltwater and freshwater, algae blooms caused by sunlight, warm temperatures and water composition can make the water look green, red or brown. Some algae contains toxins that may affect swimmers’ health.

Supervised swimming areas will also use a flag system to indicate whether it is safe to swim. 

Where can you swim?

Most waterways in France are classed as ‘free locations’, meaning that you can swim without restriction in any body of water (sea, pond, river or lake) as long as there is no rule in place saying that you cannot.

READ MORE: EXPLAINED: Can you swim in France’s largest rivers?

Basically, in locations like this, you swim at your own risk. Local authorities will post signs signifying possible and unseen dangers of swimming outside supervised areas, and it should be noted that more than six in 10 drownings happen in unsupervised swimming areas – a figure that rises to 98 percent for river or canal swimming.

Supervised swimming areas have the advantage of lifeguards on duty for certain periods of the day between June 15th to September 15th for sea swimming, and from July 1st to August 31st for freshwater swimming.

Along the French coast, swimming areas are indicated by two two-tone flags, red at the top and yellow at the bottom. This signage is supplemented by a flag which must be visible from the entire swimming area, with three colours: green indicates “supervised swimming without apparent danger”; yellow is for for “supervised swimming with limited or marked danger”; and red indicates “bathing prohibited”.

Access to these swimming areas is generally free, but the Code du Sport allows for an entry fee in the case of “physical and sporting activity establishments in which aquatic activities, bathing or swimming are practised or in which these activities are part of the provision of services”.