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8 Reasons Your Relaxing Hot Tub Is Actually Pretty Gross

Think twice before taking a soak.

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Hot tubs are very, very cozy

Swimming in any body of water exposes you to skin cells, urine, and other contaminants. Pools have a large amount of water to disperse them, but hot tubs hold less water. โ€œYouโ€™re bathing in close quarters with however many of your friends are with you,โ€ says Kelly Reynolds, PhD, microbiologist and associate professor in the public health college of the University of Arizona. With less water to dilute any contaminants, the concentration is higher in a hot tub.

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Itโ€™s hard to keep chlorine levels up to snuff

Those tight quarters also make it tough to keep up with a hot tubโ€™s chlorine demands. Chlorine sticks to skin cells, sunscreen, and body oils, meaning youโ€™re taking some out with you when youโ€™re done soaking. Every time you hop in and out, you mess with the levels even more. โ€œWhen you get out of a hot tub or swimming pool and smell chlorine on your skin, youโ€™ve taken some of that chlorine with you,โ€ says Dr. Reynolds. โ€œYouโ€™re just increasing the chlorine demand by going in and out and bringing debris into the hot tub.โ€ Public hot tubs usually get checked multiple times per day, but you probably arenโ€™t as diligent with your private one. Dr. Reynolds recommends testing the levels more often, and showering before hopping in the hot tub to rinse off any oils. Find out the healthiest shower temperature.

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Bacteria keep growing at night

โ€œIf youโ€™ve used the hot tub during the day, you introduced bacteria to the hot tub,โ€ says Dr. Reynolds. โ€œYou donโ€™t want time for those bacteria to grow overnight.โ€ She recommends shocking the water with an extra-high amount of chlorine before you head in for the night. The next day, test the water again to make sure chlorine levels are safe before you use it again. Meanwhile, learn how to clean your bathing suit without ruining it.

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Poop makes its way in

โ€œDepending on how effective you are at wiping or bathing before you swim, all of us carry some residual amounts of feces,โ€ says Dr. Reynolds. โ€œWhen you jump in the pool, that gets released into the water.โ€ The bacteria in that poop could cause stomach infectionsโ€”luckily, they can only infect via the mouth, and most people donโ€™t stick their faces underwater in hot tubs. But be extra careful if youโ€™ve had diarrhea recently. You could still be carrying those germs up to two weeks after your symptoms are gone. Learn what your bowel movements reveal about your health.

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Chlorine wonโ€™t kill all bacteria

Cryptosporidium and Giardia are parasites that can cause you to have diarrhea for weeksโ€”and both are resistant to chlorine. โ€œMost people donโ€™t know you really shouldnโ€™t swim with other peopleโ€ when infected, says Dr. Reynolds. She recommends shock-chlorinating a hot tub so the high levels can kill off the parasites, or waiting until the filtration process finishes.

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Hot tub rash is pretty common

One type of bacteria that particularly likes warm water is Pseudomonas. With an infection, you could end up with a rash called hot tub folliculitis. โ€œEverywhere you have a hair follicle, you could get a welt or a boil,โ€ says Dr. Reynolds. Some people might get just one or two welts, but others could be covered head to toe. Itโ€™s hard to treat, and even though it will go away on its own after a few weeks, the rash could leave you with scars for about a year. Try these home remedies for rashes.

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You could get a respiratory infection

Legionnaireโ€™s disease is a rare, severe form of pneumonia caused by Legionella bacteria that live naturally in water. The bacteria particularly love warm, spraying environments like home water heaters, shower aerosol mistsโ€”and hot tubs. As you soak, you could be breathing in the bacteria. โ€œYou get these little aerosol mists at the surface that youโ€™re breathing in,โ€ says Dr. Reynolds. โ€œIt creates that route of transmission.โ€

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You could get a staph infection

About a third of the population carries the bacteria Staphylococcus aureus (staph), according to the CDC. In a hot tub, any open woundโ€”even ones you didnโ€™t know you hadโ€”could let staph into your body. โ€œSmall knicks from shaving could create an entry point,โ€ says Reynolds. From there you could get a skin infection similar to hot tub rash. Even worse, a less common form of staph called MRSA is resistant to antibiotics, making the painful bumps even harder to treat. Don’t miss these signs your cut is infected.

Marissa Laliberte
Marissa Laliberte-Simonian is a London-based associate editor with the global promotions team at WebMDโ€™s Medscape.com and was previously a staff writer for Reader's Digest. Her work has also appeared in Business Insider, Parents magazine, CreakyJoints, and the Baltimore Sun. You can find her on Instagram @marissasimonian.