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Rash Decisions

Understanding the causes of skin irritation in hot tubs 

Some hot tub users suffer from rashes and irritation and assume they’re intolerant to chlorine or bromine. While it is true that some people have adverse reactions to these chemicals, there is often something else at play. Here are the seven most common causes of hot tub rashes and skin irritation.

1. Water balance 

When chlorine and bromine are mixed with water, they turn to acid and bring the pH and alkalinity down. We often find that people will balance their water on the initial fill but neglect to maintain the correct balance, and the pH will drop as they use chlorine or bromine. A pH reading below 7 is a sign that the water has become acidic. Soaking in acidic water can cause mild irritations in some bathers like itchy calves and backs, and in others, it can cause severe rashes and burns. Maintaining alkalinity and pH in proper ranges will prevent this. 

2. Reactions to nonchlorine shock  

Many doctors and professional spa retailers are unaware some people are intolerant to nonchlorine shock, also known as MPS, potassium peroxymonosulfate, and potassium monopersulfate.  

People who are intolerant to nonchlorine spa-shock may not notice any issues while in the water. However, within two to 48 hours after using the spa, they often develop a rash accompanied by severe itching on areas that were underwater. This reaction can last for up to two weeks. People don’t realize the spa water caused the rash, so they get back into the water to try to soothe the itching, further exacerbating their condition.

The solution is to drain the spa, refill it and use chlorine granules to shock the water rather than nonchlorine shock.

Common myths about hot tub-based skin irritation
Myth #1: All Rashes Are Caused by Chlorine
Not all skin irritations are a result of chlorine intolerance. Many factors, such as water balance, bacteria or other chemicals, can be to blame.
Myth #2: Stronger Chemicals Solve the Problem
Over-shocking water may lead to further skin irritation. It’s important to properly balance the spa’s chemicals.
Myth #3: All Skin Rashes Show Up Immediately
Some reactions, like intolerance to nonchlorine shock and folliculitis, may take up to 48 hours to appear after soaking in the hot tub.

3. Bacteria

The pseudomonas bacterium causes hot tub folliculitis, which is an infection of hair follicles and typically causes red, itchy bumps on the skin. Poor sanitation practices are often the cause of bacteria and will typically affect multiple bathers.   

Decontaminating your spa will rid it of bacteria. To decontaminate, super-chlorinate the water with granular chlorine or bromine. Add chlorine at a minimum ratio of 5 tablespoons per 100 gallons of spa water. For this treatment to be effective, the chlorinated water must be distributed throughout the entire plumbing system. Ensure diverter valves are midway and that all jets, valves, waterfalls, water features and aerators are open and subjected to chlorine. If your tub has a floor drain, ensure some of the chlorinated water is bled through the drain at the onset of this procedure. This is important because floor drains are a dead end in the plumbing, and the chlorine will not naturally make its way down to that part of the plumbing but the contaminant will.

Check the chlorine reading after 24, 48 and 72 hours. If at any of these intervals the chlorine is anything less than 30 ppm, treat the tub again with chlorine and start the clock over on the 72-hour period. Do not use the spa during the decontamination process.

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After 72 continuous hours of successful chlorination:

  • Remove your filter and clean it. 
  • Use a plumbing cleaning product.
  • Drain the spa.
  • Install the clean filter and refill the tub as per the spa manufacturer’s directions.
  • Maintaining proper sanitation practices will prevent future development of pseudomonas. 

4. Medication 

Medications can cause hot tub rash when soaking in hot water, particularly some heart medications. Bathers should consult their physician to see if their medication could be causing the rash.   

5. Hot water

An intolerance to hot water can cause rashes. Lowering the spa water temperature to 98 degrees or less can help to prevent this, as may using the spa for shorter durations and taking a cool shower upon exiting.

6. Combined chlorine

Once free chlorine has combined with a contaminant and broken it down, it doesn’t just vanish but converts to a byproduct called combined chlorine, also known as a chloramine. Combined chlorine doesn’t do anything except sit around and give off that “chlorine smell” that people complain of, and it can cause itchy skin and burning eyes. 

To get rid of combined chlorine, you need to shock the water, and as the combined chlorine dissipates, so will the itching, odors and burning eyes that accompany it.

7. Intolerance to halogens

Halogen-based sanitizers include chlorine and bromine. As previously stated, a lot of people think they are allergic to chlorine and bromine, but in reality, few are. For those that are, using other forms of registered sanitizers like biguanides instead of halogens will allow people to enjoy their spa again.