Hot tub folliculitis

This is the one condition on this site where the correct treatment is nothing at all. That is a genuinely useful thing to know two days after a hotel hot tub, when you are looking at a torso covered in itchy bumps and considering a walk-in clinic.

What is hot tub folliculitis?

An infection of the hair follicles by Pseudomonas aeruginosa, a bacterium that is common in the environment and does well in warm water where the disinfectant has run down.

That last part is why hot tubs specifically. Chlorine and bromine degrade quickly at hot-tub temperatures, so a tub that is not being actively tested and dosed loses its protection much faster than a swimming pool does. Pseudomonas moves in, and warm water opens your follicles and softens the skin — a good route in.

It goes by several names, all the same thing: hot tub rash, jacuzzi folliculitis, Pseudomonas folliculitis. It is also not exclusive to hot tubs. Poorly maintained pools, water slides and physiotherapy pools all do it.

How quickly does it appear, and what does it look like?

Within about 48 hours of exposure. The case literature describes itchy papules and pus-topped papules ranging from two to ten millimetres across.

The distribution is the giveaway, and it is worth knowing because it is what separates this from almost everything else:

• Worst where your swimwear was. A costume holds contaminated water against the skin long after you get out, and adds occlusion and friction on top.
• Spares the palms and soles, which have no hair follicles to infect.
• Often affects several people who used the same water within a day or two of each other.

If you can trace itchy bumps to a hot tub in the last two days and they are heaviest under where a costume sat, you have your answer and you do not need anyone to confirm it.

What is the actual treatment?

For most people, none.

The published review is direct about this: in most cases the lesions are self-limited and resolve without management in one to two weeks. That is the whole prognosis, and it holds even when the organism turns out to be resistant to whatever antibiotic was tried — the Cureus case report describes exactly that, with the rash clearing despite the treatment not being one Pseudomonas was sensitive to.

So what is worth doing:

Cool compresses for the itch. A cool damp flannel for ten or fifteen minutes. This makes you more comfortable; it does not shorten the illness, and that is fine.

Leave it alone. No squeezing, no scrubbing.

Get out of the swimwear and shower — which you have presumably already done by the time you are reading this, but it is the intervention that matters for the next time.

Wait. Mark the date. If it is not improving by two weeks, that is when it becomes a question for a clinician.

Antibiotics are not routine here, and the reason is not caution — it is that Pseudomonas is resistant to a lot of the antibiotics commonly prescribed for skin infections, so a prescription frequently changes nothing about the timeline while adding side effects. Treatment does get considered for people who are immunosuppressed, and for cases that are not following the expected course.

Why does it come back for some people?

The reviewed risk factors are worth knowing if this has happened to you more than once: female sex, changes to normal skin flora — from diabetes, immunosuppression or recent antibiotic use — how long you were in the water, and prior skin trauma such as sunburn or a thermal burn. Differences in which topical products people use appear to matter too.

Practically, the two things you control are contact time and what happens after. Shorter sessions in water you do not know the maintenance history of, and a shower with a change out of swimwear straight afterwards rather than an hour later.

If it is your own tub, this is a maintenance problem with a maintenance answer: test the disinfectant and pH regularly, and follow the manufacturer’s guidance for a hot tub rather than a pool. If it is a hotel or gym, telling them matters — if several guests have a rash, the water is the reason, and nobody else knows to mention it.

Is it this, or another post-swim rash?

Several things cause a rash after being in water, and they are distinguishable by pattern and timing.

Hot tub folliculitis — discrete bumps, each on a follicle, worst under where swimwear sat, onset within about 48 hours, itchy. Palms and soles spared.

Chlorine or bromine irritation — not spots but a diffuse redness and dryness, often with itching, appearing within hours rather than a day or two. It affects exposed skin as much as covered skin, which is close to the opposite of the swimsuit pattern.

Swimmer’s itch — from parasites in fresh water, mostly lakes and ponds rather than treated pools. Intense itching with small red spots, and it typically affects skin that was not covered by a costume, because the fabric provides some protection. Again, the inverse distribution.

Ordinary bacterial folliculitis from occlusion — damp swimwear worn for hours in the sun will irritate follicles without any Pseudomonas involved. This looks similar and follows the same self-limiting course, and the practical distinction barely matters, because the management is the same.

If it fits the first description, you have your answer. If it is diffuse redness rather than discrete bumps, it is chemistry rather than infection and a moisturiser is more use than anything else.

What if it does not clear in two weeks?

Mark the date you noticed it, because two weeks is the decision point and it is easy to lose track.

If there has been steady improvement but some bumps remain at fourteen days, that is within normal and worth another week. If there has been no improvement at all, or it is worse, that is when to get seen — not because the situation is alarming, but because the diagnosis is worth revisiting. Something following a different course is probably a different thing.

The marks are a separate question from the bumps. Faint patches where spots were can persist well past the fortnight and are not a treatment failure.

What to skip and why

Skip the antibacterial scrub. Scrubbing inflamed follicles spreads the organism across the skin and irritates a rash that was going to resolve anyway. Antibacterial washing is the right instinct for bacterial folliculitis and not for this.

Skip thick ointments over the area. Occlusion is part of how this started.

Skip the walk-in clinic on day two, unless something below applies. It is not that clinicians cannot help; it is that the honest advice on day two is to wait, and it is better to know that in advance.

Skip getting back in the same tub until whoever runs it has tested it.

Skip worrying about the marks. Faint patches where the bumps were can hang around for weeks or a couple of months, particularly on deeper skin tones. That is post-inflammatory pigmentation, not the infection persisting. If it bothers you, azelaic acid is the ingredient that works on it, over twelve to sixteen weeks.

When to see a doctor

The reason to go is a course that deviates from the expected one, not the rash itself:

• No improvement at all after two weeks, or it is getting worse.
• Fever, or feeling generally unwell.
• Spreading redness with skin that feels hot to the touch.
• A firm, painful lump forming under the skin.
• You are immunosuppressed, diabetic or pregnant.
• Ear involvement — the same organism causes a painful outer-ear infection, and that one does want treating.

Marks left behind can persist for weeks or a few months after the bumps have gone, particularly on deeper skin tones. That is post-inflammatory pigmentation rather than the infection continuing.