Fashionable hot tubs may contain the same germs as a toilet, a microbiologist has warned.
As many as one in 20 people in the UK bought a hot tub at the height of the pandemic, according to one survey.
Thousands of people use them on holiday, in hotels and spa resorts.
But relaxing in a hot tub means soaking in a mix of faecal matter, urine traces and sweat from other people’s bodies, according to Dr Primrose Freestone, from the University of Leicester.
She advises people to avoid hot tubs others have used, to shower before and after getting in one, and to stay in the tub for no longer than 15 minutes.
As many as one in 20 people in the UK bought a hot tub at the height of the pandemic, according to one survey
Dr Freestone told the Mail: ‘A hot tub does not contain the same amount of bacteria as a toilet, but it will take up the 100mg or so of faeces each person carries between their buttocks.
‘Urine and sweat will also get into the water, and so the same germs in a toilet will be in a hot tub, which is not hot enough to kill most of them.
‘People describe taking a bath as stewing in your own filth, but being in a hot tub is stewing in other people’s filth.
‘They are not quite the luxury they may appear.’
The health hazards of swimming baths have long been warned about, from verrucas to the threat of children peeing in the pool.
But hot tubs can be worse, according to Dr Freestone, as operators may be less scrupulous about checking filters and maintaining adequate disinfectant levels, while the tubs are smaller so bacteria are more concentrated.
For those determined to enjoy relaxing in a hot tub anyway, she advises using a chlorine testing strip to ensure the tub is clean.
The more strongly it smells like a swimming pool, the more dirty it probably actually is, as that strong chemical smell comes from chlorine reacting with people’s sweat.
Dr Freestone said: ‘If it smells of chlorine, that suggests more people have been in the hot tub and it has not been cleaned recently.
‘A good way to judge it is to wipe your finger along the rim and see if it is slimy with bacteria.
‘I have never used a hot tub, and do find the thought of them fairly yucky.
‘But as many people really love them, they should just be aware of the risks and have the right advice, keeping everybody safe.’
Bacteria from people’s bodies can end up in the air from steam coming off a hot tub or jacuzzi, and be inhaled by others sharing it.
The greatest risk for healthy people, according to experts, is stomach bugs, or skin irritation from chemicals in the water.
But there may be greater health risks for children, pregnant women and those whose immune systems are suppressed.
Dr Freestone advises people to use their hot tub at home, rather than public ones, and change the water after every use if possible, or if not, in accordance with manufacturers’ instructions.
She warns that similar bacterial risks apply to jacuzzis and whirlpool baths, which should be kept scrupulously clean after every use.
The good news from the microbiologist, who wrote an article on hot tubs for The Conversation, is that there is no extra threat of germs from a glass of Prosecco in the hot tub.
She said: ‘Alcohol will kill off any germs which splash into the glass, so there is no issue with having a drink in the tub at all.’