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Potassium monopersulfate (mps) and itchy skin


poolaris
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I had been using our hot tub for two weeks after filling it and balancing the ph, alkalinity and  dichlor, calcium hardness etc to correct levels. I then added 1.5 oz of MPS and waited 2 days before entering spa. Within an hour after exit I had bumps and redness on my back which itched. After a few days the itching subsided but again returned after going back into spa for 10 minutes. This makes me suspect that I may be allergic to MPS. If I am right will the MPS have diminished after five days as does chlorine, or should I drain and refill to get rid of it? I should mention that apart from adding the MPS this season I also used an silver crystal package from DimensionOne which came with the spa a few years previously and which I only recently found. Other than that, the only chemicals added were dichlor, muriatic acid,and calcium increaser.

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  • 2 weeks later...

 I'm a new and first time hot tub owner, 3 weeks now, and have spent many hours reading lots of posts at PoolSpaForum and TroubleFreePool, so I've only been learning water chemistry for the past 2 weeks. If I say anything wrong, I invite the experts to point out which part is wrong and to provide a reference. I'm sure the experts can't always be on the Internet answering the same questions over and over all the time, so I am sharing my experience and findings since I have the same issue.

Here is everything that I have found in my quest to eliminate the itch.

Yes, MPS is known to cause contact dermatitis, see:
* Gilligan, P., & Horst, A. V. (2010). Allergy to a hot tub water treatment chemical: an unexpectedly common cause of generalized dermatitis in men. The Journal of clinical and aesthetic dermatology, 3(2), 54–56.

* (2004, Sept). Cracking Tough Cases of Contact Dermatitis. The Dermatologist, 12(9): "We tested for chlorine, bromo-chloro-dimethylhydantoin, ammonium persulfate, sodium metabisulfite (used to decrease pH), and fragrances because they’re often added to spa water. The patient did not react to the chlorine or bromide, which the typical patient would. However, he did react to the sodium metabisulfite and ammonium persulfate. Ammonium persulfate was used to screen for contact allergy to the potassium persulfate used as shock treatment in the patient’s spa. The patient switched to a chlorine-based sanitizer and shock treatment and began to use other chemicals to adjust the pH levels in his spa. Soon after, his condition cleared."

* "If the patient reports using a hot tub, then patch testing with ammonium persulfate (APS), which is available from all major allergen suppliers, should be undertaken. If patch testing is positive, then the patient should be instructed to avoid exposure to hot tubs and swimming pools treated with PPMS-based shock treatments. Alternatives are to use hyperchlorination-based shock treatment or hydrogen-peroxidebased shock treatment, or to drain and refill the hot tub periodically instead of shocking it." (Gilligan, H. (2010). Allergy to a hot tub water treatment chemical: an unexpectedly common cause of generalized dermatitis in men. The Journal of Clinical and Aesthetic Dermatology, 3(2), 54–56.)

According to chem geek/Richard, "The decomposition rate of MPS at spa temperatures is about 12% per hour so is 90% decomposed after 18 hours (95% decomposed after 24 hours)" (https://www.poolspaforum.com/forum/index.php?/topic/11366-nature2-and-mps-non-chlorine-shock/)

You can get MPS test strips - see https://hottubwarehouse.com/products/aquachek-monopersulfate-test-strips-561682a - first 2 shades = low, middle 2 shades = ok, last shade = high. Nature2 also sells MPS test strips. If you are allergic to MPS or another ingredient in the chlorine-free shock, you really should do a full drain.

However, I would bet that you aren't keeping your chlorine levels sufficiently high enough on a daily basis.

Aside from MPS, other common sources of skin irritation are:
1) Various bacteria:
* Pseudomonas aeruginosa (Osborne, E., Bilalian, C., Cussans, A., & Ostlere, L. (2020). Pseudomonas folliculitis: a complication of the lockdown hot tub boom? Lessons from a patient. The British journal of general practice : the journal of the Royal College of General Practitioners, 71(702), 43–44. https://doi.org/10.3399/bjgp21X714605)
* Mycobacterium Intermedium (Edson, R. S., Terrell, C. L., Brutinel, W. M., & Wengenack, N. L. (2006). Mycobacterium intermedium granulomatous dermatitis from hot tub exposure. Emerging infectious diseases, 12(5), 821–823. https://doi.org/10.3201/eid1205.051281)
* Legionella (Barton, M. (2017). Legionellosis following water birth in a hot tub in a Canadian neonate. Canadian Medical Association Journal (CMAJ), 189(42), E1311–E1313. https://doi.org/10.1503/cmaj.170711)
* Cercarias larvae (Tracz, E. S., Al-Jubury, A., Buchmann, K., & Bygum, A. (2019). Outbreak of Swimmer's Itch in Denmark. Acta dermato-venereologica, 99(12), 1116–1120. https://doi.org/10.2340/00015555-3309)
* Staphylococcus aureus (Blicharz, U. (2020). Is itch intensity in atopic dermatitis associated with skin colonization by staphylococcus aureus? Indian Journal of Dermatology, 65(1), 17–21. https://doi.org/10.4103/ijd.IJD_136_19)

You didn't mention your exact pH, FC, CC, TC, and CD numbers. Is your FC between 3-5ppm before you get in? Five days of no chlorine is more than enough time for bacteria to repopulate. On a weekly basis or more frequently, do you sustain a shocking level of FC for over 4 hours? The shock FC ppm depends on your CYA; higher CYA means higher FC required to shock (https://www.troublefreepool.com/threads/chlorine-cya-chart.2177/, https://app.poolcalculator.com/, https://www.troublefreepool.com/calc.html).

If you are using dichlor exclusively, your CYA levels may be already too high, requiring more chlorine to do the same amount of sanitization. The most practical way to lower CYA in a spa is to drain and replace with fresh water. Exposure to sunlight/UV breaks down CYA, but according to the 2021 Bullfrog Owner's Manual pages 13, 38, and 46, "WARNING: An empty spa (spa without water in it) must not be left exposed to sunlight as shell damage may occur. Once the spa is unwrapped, fill spa with water immediately or shade the spa with cover to prevent direct exposure to sunlight" (https://1tuyvq3ivrlq1h927b2gtsql-wpengine.netdna-ssl.com/wp-content/uploads/2020/12/2021-Bullfrog-Owners-Manual-rev1.1.2-web.pdf). Perhaps an in-line UV sanitizer could help knock CYA levels down enough to allow for use of dichlor tabs through a dose-limiting float feeder.

High pH reduces effectiveness of chlorine (https://www.poolcalculator.com/the-relationship-between-pool-chlorine-and-ph/). Hypochlorous acid is what kills bacteria. "At a pH of 7 free chlorine consists of 75 per cent hypochlorous acid and 25 per cent hypochlorite ions. At a pH of 7.8 free chlorine consists of just 28 per cent hypochlorous acid and 72 per cent hypochlorite ions. It can therefore be seen that a swimming pool with a pH of 7 and a free chlorine level of just 0.5ppm has the same sanitising effect as a pool with a pH of 7.8 and a free chlorine level of 1.35ppm." This is why it is necessary to first adjust the pH prior to adding chlorine. Source: Pool industry pioneer and chemistry expert David Lloyd from International Quadratics. The Bullfrog Owner's Manual page 38 concurs, stating "Always test, and adjust the pH level before you test and adjust the sanitizer level."

To eliminate the possibility of excessive bacteria causing the itch, get your pH closer to 7, shock with chlorine, then hold this shock level for at least 4 hours, but multiple days would be better to knock the bacteria/biofilms down sufficiently. Then you can run the jets or add some borax to raise pH to a more comfortable 7.4-7.6 for regular use, and then never, ever, let FC go below 3ppm, even when using a mineral/silver additive/filter that claims to enable low chlorine sanitization. Consider the mineral/silver as a second or third layer of defense for when chlorine doesn't work, and not your primary sanitization method.

If it's a new tub (you mentioned it was filled 2 weeks ago), it will likely come with all kinds of bacteria from factory wet-testing, transportation across the country, and storage by your local dealer over many months. Even if it's a used tub sitting around empty, you likely have bacteria and biofilms inside the plumbing, and this bacteria can be the cause of skin irritation, coming back very quickly after your chlorine levels get below 2ppm. You need to clear out the biofilms in the plumbing with Ahh-some, kill the bacteria it dislodges with a shocking amount of chlorine, drain, repeat as needed. After refill, always maintain a FC level of 3-5ppm with a 20-40 CYA level, and chlorine-shock to 10ppm once a week or more. Super Sanitation aka Shock is recommended weekly per the Bullfrog Owner's Manual, as "Normal sanitation does not eliminate non-filterable wastes, such as perspiration, oils, hair sprays, etc., which may build up in the water. These substances make the water unattractive, and can interfere with sanitizer effectiveness"

If you want to test how long it takes for chlorine to knock out a biofilm, wait for a biofilm to form in your toilet, then drop some dichlor or trichlor tabs in your tank. At the rate I'm seeing, it will take weeks. Ahh-some to dislodge the bacteria and chlorine shock to kill them is the only way.

2) Other sulfates:
* There are many non-chlorine shock products on the market, many of them are wishy-washy on the amount of MPS, not to mention the full ingredient list. Some non-chlorine shock MSDS sheets show potassium hydrogen sulfate (10-30%), sodium carbonate (10-30%), magnesium salt of carbonic acid (1-5%), potassium persulfafe (1-5% and a known skin irritant), in addition to the primary ingredient monopotassium salt of peroxymonosulfuric acid (30-60%). Some companies I reached out to told me their product is 60-80% MPS, which is slightly hard to believe if you look at the prices of 100% MPS from a chemical supplier, but I digress.

* Dry acid products for reducing pH are generally sodium bisulfate and may also contain sodium metabisulfite, a known skin irritant.

To rule out sulfates, do a complete drain and don't add that silver crystal package, don't add any products containing any kind of sulfates, and don't add any chlorine-free shock products that don't list fully itemize their ingredients and percentages.

3) Chlorine/bleach itself. Does your skin get dry/irritated when showering daily with city-chlorinated tap water, or when wearing laundry whites that were bleached and not rinsed really well?

To rule out chlorine, you could try switching to bromine, but note that research shows more people are allergic to bromides than to chlorine, and bromine results in higher total amounts of toxic disinfection byproducts than chlorine (Chowdhury, A. (2014). Disinfection byproducts in swimming pool: Occurrences, implications and future needs. Water Research (Oxford), 53, 68–109. https://doi.org/10.1016/j.watres.2014.01.017)

4) pH. Too low is a skin irritant, too high is a skin irritant. The CDC recommends pH 7.2-7.8 and NOT using cyanuric acid or chlorine products with cyanuric acid in hot tubs/spas. Source: https://www.cdc.gov/healthywater/swimming/residential/disinfection-testing.html

"Some hot tub users may find it is more comfortable to keep a pH slightly elevated – closer to 7.6 on the recommended 7.4 to 7.6 range because the hot water can be more likely to cause irritation if it is too acidic." Source: https://www.poolcalculator.com/what-should-ph-levels-be-in-swimming-pools-and-hot-tubs/

5) Hot water. Some people's skin just don't like being in hot water. To rule this out, have a nice hot soak in your bathtub at the same temperature as your hot tub and for your typical soak duration and see what happens.

I did a test on myself to rule out MPS. I've gotten into the tub 15 minutes after adding 26g MPS (the Nature2 recommended pre-soak dosage for 1643L) with my FC at 4. Nothing unusual happened after, so I conclude I'm not allergic to the MPS (Spa Pure Shock from Home Depot, unknown ingredients aside from MPS, and unknown MPS %).

My itching issues are generally solved now. Itchy skin with bumps appearing 1-3 days after is correlated with FC levels being 0-2ppm after 12-48 hours, likely causing bacteria growth, solved by adding dry acid to keep pH closer to 7.4 instead of 7.8 (resulting in my true target pH of 7.6 after the pH rise from using jets), plus dosing of 10.8% chlorinating liquid to 10-15ppm instead of 5ppm as my owner's manual suggested, using the pool calculator to factor in my CYA, TA, etc. Also changed my ozonator+filter cycle to start as far as possible from the post-soak chlorine dose, letting more chlorine stay active overnight instead of being consumed by ozone. This results in 3-4ppm FC up to 48 hours later.

My itchy skin without bumps 2-24hrs afterwards is sensitivity and dryness caused by bleach/chlorine and/or hot water (spa is kept at 37-38C), and this is corrected by applying moisturizer to the affected areas. Note that laundry washed with bleach has always irritated my skin, so I know for sure that bleach/chlorine residues causes contact dermatitis for me.

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On 12/29/2020 at 10:43 AM, poolaris said:

I also used an silver crystal package

Red flag here! What FC are you maintaining. While MPS can cause a skin reaction I suspect that if you are running low chlorine because of the silver you might be suffering from "hot tub itch" caused by pseudomonas.

https://www.healthline.com/health/hot-tub-folliculitis

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On 1/10/2021 at 12:09 AM, 5tan said:

'm a new and first time hot tub owner, 3 weeks now, and have spent many hours reading lots of posts at PoolSpaForum and TroubleFreePool, so I've only been learning water chemistry for the past 2 weeks. If I say anything wrong, I invite the experts to correct me.

So much misinformation here. I don't know where to start. FWIW, I was one of the original Mods at TFP and wrote much of their pool school. However my name was taken of when the board was sold to it's current owner and we had a bit of a disagreement.

FYI, the chlorine/cya chart was originated by Ben Powell at PoofForum, as was much of the information that started TFP, such as the use of bleach,borax, and baking soda for swimming pools. FWIW, I was also a senior contributor at PoolForum before TFP even existed and much of the info on the use of borate originated there, mostly from ChemGeek and myself based on a question from an Industry contributor there as to whether the products Proteam Supreme and BIoguard Optimizer (both the pentahydrate form of borax) actually lived up to all the claims made for them. They do.

I understand you desire to help but until you learn a bit more I would suggest not just quoting from other sources that may or may not be applicable to the OP's question. Most of what you posted has nothing to do with the possible causes of the skin rash the OP is asking about.

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On 1/10/2021 at 12:09 AM, 5tan said:

 I'm a new and first time hot tub owner, 3 weeks now, and have spent many hours reading lots of posts at PoolSpaForum and TroubleFreePool, so I've only been learning water chemistry for the past 2 weeks.

2 weeks does not make you an expert. Please refrain from giving advice on water chemistry until you learn a lot more.

On 1/10/2021 at 12:09 AM, 5tan said:

Yes, MPS is known to cause contact dermatitis

However, it is rare, generally not localized to one area of the exposed skin, and is not as the OP described. While it is possible that it is contact dermatitis other more likely options need to be ruled out and more information is needed such as water test results before jumping to a conclusion.

"Potassium monopersulfate (MPS) is widely used in spa and pool "shock" treatments, yet contact dermatitis associated with MPS has been rarely reported. "

https://pubmed.ncbi.nlm.nih.gov/18413112/

On 1/10/2021 at 12:09 AM, 5tan said:

However, I would bet that you aren't keeping your chlorine levels sufficiently high enough on a daily basis.

I already alluded to that in my previous post. Is this one of your 'edits' for my benefit?

On 1/10/2021 at 12:09 AM, 5tan said:

Exposure to sunlight/UV breaks down CYA

No, It doesn't.

On 1/10/2021 at 12:09 AM, 5tan said:

Perhaps an in-line UV sanitizer could help knock CYA levels down enough to allow for use of dichlor tabs through a dose-limiting float feeder.

 

This shows that you don't know the first thing about chlorine sources. Trichlor is a tablet used in a feeders and is not normally recommended for spas because of its extremely low pH. Dichlor is a granular product that is only slightly acidic that is usually used in spas that is broadcast on the water surface. A UV unit will not get rid of CYA. UV breaks down unstabilized chlorine very quickly. CYA stabilizes chlorine against degradation from UV. You got that backwards.

On 1/10/2021 at 12:09 AM, 5tan said:

High pH reduces effectiveness of chlorine (https://www.poolcalculator.com/the-relationship-between-pool-chlorine-and-ph/). Hypochlorous acid is what kills bacteria. "At a pH of 7 free chlorine consists of 75 per cent hypochlorous acid and 25 per cent hypochlorite ions. At a pH of 7.8 free chlorine consists of just 28 per cent hypochlorous acid and 72 per cent hypochlorite ions. It can therefore be seen that a swimming pool with a pH of 7 and a free chlorine level of just 0.5ppm has the same sanitizing effect as a pool with a pH of 7.8 and a free chlorine level of 1.35ppm."

This is ONLY true if there is NO CYA present. OP mentioned dichlor use. Dichlor adds 9 ppm CYA for eery 10 PPM of FC added. This effect is cumulative so if the spa was shocked twice and the FC raised from 2 ppm to 12 ppm each time that means 20 ppm FC have been added along with 18 ppm CYA. The effect of adding CYA basically take pH out of the equation in terms of chlorine's effectiveness. Here is a white paper written by RIchard Falk. Check out the chart on page 8.  You might know him as chem geek. I know him as Richard.

https://cdn2.hubspot.net/hubfs/3831534/Chlorine-CYA.pdf

On 1/10/2021 at 12:09 AM, 5tan said:

To eliminate the possibility of excessive bacteria causing the itch, get your pH closer to 7, shock with chlorine, then hold this shock level for at least 4 hours, but multiple days would be better to knock the bacteria/biofilms down sufficiently. Then you can run the jets or add some borax to raise pH to a more comfortable 7.4-7.6 for regular use, and then never, ever, let FC go below 3ppm, even when using a mineral/silver additive/filter that claims to enable low chlorine sanitization. Consider the mineral/silver as a second or third layer of defense for when chlorine doesn't work, and not your primary sanitization method.

Not even close.  Please don't talk about things with which you have no experience. 

On 1/10/2021 at 12:09 AM, 5tan said:

It can therefore be seen that a swimming pool with a pH of 7 and a free chlorine level of just 0.5ppm has the same sanitising effect as a pool with a pH of 7.8 and a free chlorine level of 1.35ppm." This is why it is necessary to first adjust the pH prior to adding chlorine. Source: Pool industry pioneer and chemistry expert David Lloyd from International Quadratics. The Bullfrog Owner's Manual page 38 concurs, stating "Always test, and adjust the pH level before you test and adjust the sanitizer level."

Once again, only when there is NO CYA present. FWIW, the reason you want to adjust pH first is because many test kits and strips use a pH reagent that will read high when the sanitizer is above 3-5 ppm and read high or give an off color (the dye converts to chlorphenol red which has similar color changes as phenol red but in the pH range of 4.8 to 6.7  and give the impression that pH is high when it can be actually be dangerously low or, in the case of bromine, bromophenol red with a range of 5.2 to 6.8) so you want to adjust pH first. This is also why you NEVER try to adjust or even measure pH when shocking. Taylor reagent is accurate up to 10 ppm sanitizer level because they incorporate a chlorine neutralizer into their formulation.

On 1/10/2021 at 12:09 AM, 5tan said:

To rule out sulfates, do a complete drain and don't add that silver crystal package, don't add any products containing any kind of sulfates, and don't add any chlorine-free shock products that don't list fully itemize their ingredients and percentages.

Sulfites can cause dermatitis but it does not present the same as the OP described. I have never heard of any reaction to sulfate ion. Not saying it does not exist but I have yet to come across anything that alludes to it.

On 1/10/2021 at 12:09 AM, 5tan said:

3) Chlorine/bleach itself. Does your skin get dry/irritated when showering daily with city-chlorinated tap water, or when wearing laundry whites that were bleached and not rinsed really well?

Really? I suggest you google 'beach baths for eczema'. This is a bath of a strength around 50 ppm and is often prescribed for babies. Chlorine is NOT a known sensitizer. Bromine can be but it is rare.

On 1/10/2021 at 12:09 AM, 5tan said:

The CDC recommends pH 7.2-7.8 and NOT using cyanuric acid or chlorine products with cyanuric acid in hot tubs/spas.

This is only in their handout for home users that don't understand the chlorine/cya relationship and the fact that hot tubs, unlike outdoor pools, are not exposed to sunlight for long periods. If you haven't figured out by now there is a LOT of misinformation about pool/spa care for various reasons. For example, the effects of CYA on chlorine have been knows since the 60s and even published in the JSPSI (The Journal of the Swimming Pool and Spa Industry) back then but were widely suppressed by the makes of stabilized chlorine products, notably Chemtura, because of the fear it would cut into their profits.

On 1/10/2021 at 12:09 AM, 5tan said:

Some hot tub users may find it is more comfortable to keep a pH slightly elevated – closer to 7.6 on the recommended 7.4 to 7.6 range because the hot water can be more likely to cause irritation if it is too acidic."

7.8 is often a more realistic place given the amount of aeration in a tub if you want pH stability. Also most tubs do best when the TA is below 60 ppm to minimize the outgassing of CO2, which is the main cause of pH rise. IF you are using a secondary borate buffer then the pH should rest right around 7.7 and should only be dropped with it climbs above 8.0 and should not be dropped lower than 7.6. This assumes no MPS or acidic chlorine sources.

 

On 1/10/2021 at 12:09 AM, 5tan said:

Note that laundry washed with bleach has always irritated my skin, so I know for sure that bleach/chlorine residues causes contact dermatitis for me.

More likely detergent residue or an oxidation byproduct that formed between the bleach and organics in your clothes. Think combined chlorine/non volatile chloramines. Try a second rinse in your washer.

 

On 1/10/2021 at 12:09 AM, 5tan said:

Edited by 5tan
References to address waterbear's concerns about misinformation/misattributions

Nice try but no cigar.

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@5tan it's great that you want to help others, but you should only do so on subjects that you are knowledgeable on. I have been repairing spas professionally for 26 years and have never met anyone, including chemical manufacturers reps, that possess half the know-how on water chemistry as @waterbear. I'd suggest you research his posts, there are many on this forum in the water chemistry section, for an expert education. 

For what it's worth, I too argued with him when I first started here, based upon my industry experience, education, and Certified Pool Operator course. I have since learned how woefully undereducated I was in water chemistry, thanks primarily to him. There is now only one subject that we disagree on, and he's probably right about that one too.😉 

I have learned to refer chemistry questions to him, it's just better all the way around that way. He has forgot more on the subject than I am ever likely to know.

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9 minutes ago, RDspaguy said:

There is now only one subject that we disagree on, and he's probably right about that one too.😉 

Hi ho Silver away! ;) (if you are not old enough to get the reference it from The Lone Ranger but that's not what I'm referring to!)

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  • 2 months later...

FYI...was having rash problems for several months.  Started in the thighs but then spread to the chest and lower legs as well.  Rashes got so bad could hardly use the tub.  After some online research, did a hail mary and took MPS out out the picture.  That did the trick - rashes disappeared.  

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  • 8 months later...

MPS rash is real! 

I had what was similar to poison ivy mostly on the back of my calves that would not go away. I removed MPS and replaced it with a regular dichlor shock and my rash went away quickly. After six months of feeling like I have mastered my chemistry in the tub with dichlor, I switched it out with MPS and within a week I am back to a poison ivy like rash on the back of my calves. 

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