Just how gross are hot tubs? Depends how you feel about bathing in feces, urine and fungi

‘Whatever we have on our skin we deposit into the warm water swirling around us, including the 100mg or so of feces usually present between our buttock cheeks’

For many centuries we have bathed in communal waters. Sometimes for cleanliness but more often for pleasure. Indeed, in ancient Greece, baths were taken in freshwater, or sometimes the sea – which was thought of as a sacred place dedicated to local gods and so was considered an act of worship. But it was the Romans who created state-sponsored aqueducts to allow for large-scale public baths. These were mainly used for relaxation but also for more private pleasures, too. Yes, the public baths were often where Romans did the dirty deed – sometimes with their bath attendant slaves.

Two millennia on, we’re still attracted to bathing communally, though many people now have their own hot tub or Jacuzzi – sales of which went up massively during the pandemic.

For those that don’t have their own hot tub, there’s always the local gym or spa. And many hospitals also feature one too. This is because Jacuzzis are often used therapeutically for relieving and treating joint inflammation in rheumatoid and osteoarthritis patients. Indeed, in many ways Jacuzzi bathing is regarded as a luxury treat experience – one that’s both relaxing and rejuvenating.

The warmth of the water within the hot tub naturally widens blood vessels, which helps our muscles to relax and eases sore joints. As well as being physically comforting, a sense of psychological wellbeing may also be created by the buoyant warm water and the companionship of those who share the bathing experience.

Bacteria, viruses and fungi in hot tubs

But it’s also worth bearing in mind that when we enter the waters of a Jacuzzi whatever we have on our skin we deposit into the warm water swirling around us. This includes the 100mg or so of feces that is usually present between our buttock cheeks. This means that while you’re relaxing in the hot tub’s warm water, you’ll likely breathe in or swallow your Jacuzzi partner’s body’s bacteria, viruses and fungi.

The more people in the Jacuzzi, the higher the levels of feces and sweat shed into the water (and urine if anyone has peed in the water). And these bodily deposits can be used by the bacteria as direct nutrients.

As Jacuzzi owners are advised to change the water in their hot tubs only around every three months, bacteria will grow. For microbiological safety, most Jacuzzis that recirculate water have microbe-removing filters and water is treated with microbicides (which kill germs) such as chlorine, bromine, or other disinfectants to control bacterial numbers.

Such chemicals are toxic and cause skin and eye irritation. This is why Jacuzzi users are advised to shower after bathing (and should also shower before, too). The temperature of the water within a Jacuzzi (around 104°F or 40°C can also cause potentially serious health problems such as core overheating which can lead to feeling faint or even loss of consciousness and potentially drowning.

This is especially the case for pregnant women and children, along with people with underlying health conditions, who should always check with their doctor before using a hot tub. This is why most sessions are advised to last no more than around 15 minutes and should be supervised.

Dirty or filthy?

While personal Jacuzzis may be relatively safe microbiologically, public (hotel or spa) Jacuzzis can potentially be very high in infection-causing bacteria (germs), particularly if water is recycled.

The root problem is poor public compliance with personal hygiene guidelines and inadequate water treatment maintenance. Improperly maintained public Jacuzzis can lead to outbreaks of infections by human-associated bacteria which survive well in water.

These include E.coli, Staphylococcus aureus, Pseudomonas aeruginosa and Legionella pneumoniae. These Jacuzzi pathogens can cause gut infections, diarrhoea, septicemia, skin infections, urinary tract infections and respiratory infections, including Legionnaires’ disease.

Legionella bacteria are particularly found in the water droplets within the hot tub steam and inhaling the contaminated steam could lead to the development of life-threatening pneumonia.

Indeed, the infection risk from hot tubs is so significant that in the U.S., the Centers for Disease Control has released official advice on how to prevent this.

So if you do still want to enjoy a hot tub or a Jacuzzi, is there a way of telling if it’s safe or not? There are some clear signs of a germ-filled Jacuzzi. When urine and other body fluids such as sweat mixes with the chlorine used to disinfect Jacuzzi waters it creates an irritant, a pungent chemical called chloramine, which is what causes sore eyes when swimming in public pools.

The more bathers that deposit their bodily fluids the stronger the smell of the chloramine (which smells a bit like bleach) and the greater the likelihood that the spa or hotel Jacuzzi has low levels of disinfectant and high levels of bacteria. So if the hot tub is strong smelling, the chances are it may be unsafe to use – even if the waters look clean and clear, though it’s also worth noting that the water does become murkier the longer it goes without chemicals.The Conversation

Article by Primrose Freestone, Senior Lecturer in Clinical Microbiology, University of Leicester

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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  1. As a Certified Commercial Pool Operator, I can attest that hot-tubs and spas are much more prone to carrying bacteria and disease for several reasons. Less water than a swimming pool, higher temperature, and enclosed areas all contribute to the problem. Think about this: the reason you smell “chlorine” at facilities is because the chlorine is OXYDIZING the bacteria in the water, creating COMBINED CHLORINE. Fresh, untethered chlorine molecules are called FREE CHLORINE. The more chlorine you smell, the higher the amount of bacteria and COMBINED CHLORINE in the water/atmosphere. Health departments specify 1-3 PPM of free chlorine in pools, and 5-7 PPM in spas and hot tubs.

  2. Public baths are a favorite among the Japanese. An easy solution helps them resolve a similar issue. Before getting into the bath, bathers scrub themselves with soap. Problem solved.

  3. This is why I have always limited my relaxation endeavors to saunas and steam baths, rather than pools or jacuzzis or hot tubs.

  4. This is why we invented the EPA Registered Hot Tub Serum and AhhSome Hot Tub Plumbing Cleaner. Read about biofilms and other ways you can make your hot tub overwhelmingly healthy with the clearest water ever and hardly any foaming.

  5. I was once in the hot tub in our local aquatic center. A friend was also there. There was a big fuss going on up at the front desk. Turned out that the 500,000 customer had just come through the door.

    “Wow,” my friend said. “Just think! There have been a million armpits in this water. ” I nearly died laughing.

  6. I blame a spa hot tub for an ear infection in my left ear 40 years ago which eventually led to hearing loss . I had an infection on my leg for 6 years and was diagnosed incorrectly by numerous doctors and dermatologists. Everything from old age to edema to staph… Finally a Dr online gave me a fungus med for folliculitis and it was gone overnight !
    I never used to shower after the hot tub which I blame myself. I still use my spa gym hot tub for my back and it helps . THis article gave me some info on the smell ..many hot tubs give off that pungent chemical called chloramine. Good to know!

  7. To the author who walks around with a 100mg of feces between his buttocks. Take a damn shower you filthy bastard.

  8. Great article!
    I’m a retired public health infectious disease investigator.
    A local, now closed, hot tub establishment was the source of numerous herpes simplex 2 (genitals) infections as people slid their buttocks on the edges getting in and out. We cultured and found most of the diseases listed in the article, including potentially deadly organisms like legionella and E.Coli.

  9. Reading these Karen comments is hilarious, thank you for the laughs. You people willingly would stick a substance into your arm that a government whos sponsored by BIG PHARMA says is safe, but freak over a jacuzzi. Its rich! Bunch of scared internet humans, how did we ever survive without all these useless studies?

  10. Your article is very misleading and makes many false assumptions. You need to use quantifies and not assume all hot tubs are the same. Poorly written.

    1. Don’t have to drink it, all you need is the moisture (some airborne) to get Into an abrasion, eye, nostril, mouth or genital area.

  11. Basic etiquettes of a hot tub lifestyle and very few joys in life beat a hot tub lifestyle
    – Water runs through filtration
    -Drink plenty of water while in the hot tub- avoid alcoholic drinks
    -Always shower before and after using a hot tub

  12. Like public events, cities, government, and doctors; stay away from public pools for your personal safety and physical safety.

  13. Disclaimer, I’m no chemist but chloramine is used in water treatment as an alternative to chlorine. I understand chlorine bonded to ammonia produces chloramine and that is how free chlorine in a spa mixed with human soup makes chloramine but why doesn’t that disinfect as chloramine in drinking water does?

    1. Safest hot tub is the cheep one you can buy , use and properly maintain, at your own house. Assuming anyone who uses it showers before and doesn’t use it as a toilet. Same thing with my pool. The solution to pollution is not dilution.

    2. The big concern is trichloramine formed primarily by reaction of the chlorine additive and urea from urine and less so sweat. Simple answer if you “smell” chlorine someone peed in the pool. This is the typical chloramine discussed in pool chemistry. Sidebar I am no chemist either.

  14. I’m done with public jacuzzis. It’s not worth Legionairres Disease. If people were to shower before jumping in, the water would be cleaner. And for the love of God, don’t pee in the jacuzzi. Gross!

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