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What is “Hot Tub Rash”?

Pseudomonas in hot tub

When you get into a hot tub, the only thing on your mind might be to relax and enjoy the experience.  You can smell the chlorine and the temperature is comfortably high so you need not worry about germs, right? Wrong! There’s a bacterium that can live in hot tubs and has been colloquially referred to as “hot tub rash”.  This blog post will talk about Pseudomonas aeruginosa, the bacteria responsible for “hot tub rash”. 

Pseudomonas aeruginosa

P. aeruginosa is a Gram-negative, aerobic bacteria.  That’s a lot of science talk but let’s break it down. Gram-negative is a group of bacteria that have thinner cell walls and are typically harmful to humans. E. coli is an example of another Gram-negative bacteria. Aerobic means that this bacteria requires oxygen to live. Gram-positive bacteria on the other hand have thicker cell walls.

P. aeruginosa is naturally found in water, soil, and vegetation in our environment. Interestingly, it can also be isolated from a healthy person’s skin, throat, or stool. Since it can live in our natural environment and even in our bodies, it is difficult to escape this bacteria.  We run into serious problems when P. aeruginosa infects medical equipment. Since this bacteria can be found pretty much anywhere, it may be difficult to keep it out of a healing wound which can cause infections. Individuals with compromised or weakened immune systems are more susceptible to these bacterial infections. 

“Hot Tub Rash”

Hot tubs and spas should be cleaned and treated with chemicals to ensure that no bacteria live in the tub. Unfortunately, this ubiquitous bacteria cannot be kept from our favorite hot tubs all of the time.  If a hot tub is contaminated with P. aeruginosa, it can gain access through compromised skin and infect an individual. Infected skin will result in a rash, which may show up a few days after being in a contaminated hot tub. The rash is usually worse in areas that the swimsuit covered and it may look like red spots.  The skin may be bumpy and itchy and blisters may form around hair follicles. 

If you get “hot tub rash” (hot tub folliculitis), know that the rash typically goes away on its own in a few days.  As with any other health problem, if the rash does not go away or gets worse, talk to your doctor. 

Preventing “Hot Tub Rash”

To prevent “hot tub rash”, practice good sense and good hygiene like taking a shower with soap immediately after. Take off and wash your swimsuit after getting into a hot tub. Avoid shaving or plucking hair before entering a hot tub as these activities can compromise the skin and help the Pseudomonas bacteria gain access. Make sure that you are only getting into hot tubs that follow good maintenance practices.  These practices include checking the pH and free chlorine levels in the pool to ensure that the right amount of disinfectant is being used. Generally hot tubs should have free chlorine levels between 2-4 ppm.  


P. aeruginosa is a common bacteria that can cause serious problems in hospital settings, especially for those with weakened immune systems. It can also cause less severe  but still uncomfortable rashes when the infection comes from contaminated hot tub water. Practice good hygiene when using hot tubs and avoid them altogether if your skin is already compromised in any way. Indoor Science can provide P. aeruginosa testing for spas and pools; contact us if you have any concerns or questions.

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”