Hot Tub Safety: Risks and Side Effects to Know

Disadvantages of hot tubs older adults should consider

Aaron Kassraie,

AARP

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En español

Published May 18, 2022

/ Updated May 22, 2024

Close-up shot of hot tub at spa. People sitting on poolside in the background.

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For many vacationers, unwinding means indulging in a soothing soak in a hot tub at a hotel, resort or vacation rental. However, before you dip your toes, especially if you’re an older adult, consider the potential health risks associated with using a public hot tub.

A report from the Centers for Disease Control and Prevention (CDC) from 2015 to 2019, found a total of 208 confirmed outbreaks of illness associated with “treated recreational water,” primarily involving public swimming pools, hot tubs and water playgrounds. These outbreaks resulted in 3,646 cases of illness, 286 hospitalizations and 13 deaths. Although most outbreaks occurred in June, July or August, health experts believe the actual numbers may be significantly higher since many cases go unreported.

Hot tubs can be a particular concern for vacationers. During the study’s five-year period, 1 in 3 water-related outbreaks were connected to hotels or resorts, according to the CDC. Among those, the majority were associated with hot tubs (70 percent).

Read on for health-related reasons you may want to avoid hot tubs, especially if you’re an older adult.

Who should avoid hot tubs?

It may come as no shock that your body temperature rises when you’re in a hot tub. But the heat may put stress on the heart of someone with heart disease. Usually, the body produces sweat to cool you down, but this process is less effective in a hot tub, making it easier to overheat. As a result, your blood vessels expand to try to release the heat, diverting blood from your core and increasing your heart rate.

For those with heart disease, this may lead to:

Low blood pressure (or, if you have blood vessel disease, increased blood pressure)
Dizziness
Nausea
Irregular heart rhythms
Poor blood flow
Heart attack

Certain medications can also put you at higher risk for heat-related health problems. For example, blood pressure medications such as beta-blockers can slow the heart rate, interfering with the body’s ability to cool itself. And diuretics can increase salt and water excretion, putting you at greater risk for dehydration and heat exhaustion.

Additionally, people who have epilepsy or seizure disorders should always use a hot tub in the presence of someone they trust who can assist in case of an emergency. Pregnant women are advised to avoid hot tubs because it may harm the fetus, especially during the first trimester, according to the Cleveland Clinic.

Dangers of alcohol and substance use

Since the heat from a hot tub expands blood vessels, causing blood pressure to drop, people who already have low blood pressure can pass out in a hot tub, which can lead to drowning. Drinking alcohol while using a hot tub can also combine with the heat to lower blood pressure and impair judgment.

Feeling woozy, combined with slippery surfaces, can cause slip-and-fall accidents and an increased drowning risk if mobility, muscle or balance issues are exacerbated while enjoying a soak.

The CDC recommends that hot tubs be no warmer than 104 degrees Fahrenheit.

Germs common in hot tubs

The CDC warns hot tub users to avoid swallowing the water or even getting it in their mouths. Why? Because germs in the water can cause unpleasant and even life-threatening conditions.

Start with cryptosporidium, or crypto for short. The parasite, which lives in fecal matter, can cause gastrointestinal illnesses, including diarrhea. Crypto can be spread by an infected person using a hot tub. Older adults, as well as young children, pregnant women and people with compromised immune systems, are particularly susceptible. Anyone with diarrhea should avoid going into a hot tub to prevent the spread of crypto.

Even more common in hot tubs is Legionella pneumophila, a bacterium that can cause Legionnaires’ disease, a pneumonialike lung infection that is potentially serious, particularly for those ages 50 and older. Symptoms of Legionnaires’ disease include:

Cough
Shortness of breath
Fever
Muscle aches
Headaches

In 2018 alone, health departments reported nearly 10,000 cases of Legionnaires’ disease. However, because the illness is typically underdiagnosed, it is believed the actual number may be up to 2.7 times higher than what was recorded.

Identifying a Healthy Hot Tub

Use your senses. If a hot tub smells like chlorine, that doesn’t mean it’s clean. In any treated water in a hot tub, swimming pool or water playground, that distinct smell occurs when chlorine mixes with an excess of urine, sweat and other contaminants.

The sides of a hot tub should not feel sticky or slippery.

Make sure you hear the pumps and filtration systems to ensure that they are working.

Conduct your own inspection. Before going into the water, review the inspection score of a hot tub, either online or physically posted nearby. Alternatively, test strips to check the chlorine, bromine and pH levels can be purchased at hardware, pool supply or similar stores. Follow these guidelines:

Chlorine should be at least 3 ppm (parts per million) in hot tubs.
Bromine, an alternative to chlorine, should read at least 4 ppm in hot tubs.
The pH level represents how effectively germs are killed and should be 7.2 to 7.8.

Remember to shower for one minute before entering a hot tub. Doing so should remove about 70 percent of contaminants from the skin, according to the Centers for Disease Control and Prevention.

A milder infection resulting from legionella known as Pontiac fever also results in fever and muscle aches.

Pseudomonas is another bacteria partial to warmer water temperatures that can survive and multiply in a hot tub’s biofilm. But rather than a respiratory infection, this germ can cause what’s known as “hot tub rash.” The skin infection can affect hair follicles and result in red, itchy skin and pus-filled blisters.

“You develop a rash basically wherever your skin came in contact with the hot tub water, so people will often find a rash pattern similar to their bathing suits,” Michele Hlavsa, chief of the CDC’s Healthy Swimming Program said. “The bathing suit is holding water against their skin.”

To lessen the likelihood of hot tub rash, make sure to remove your swimsuit, wash it, and take a shower with soap after using a hot tub.

Potential side effects of hot tubs

While there’s a risk of contracting Legionnaires’ disease or Pontiac fever by swallowing contaminated water, there’s an even greater risk presented by inhaling contaminated water vapor emitted from a hot tub. That means if you sit near a hot tub without ever going in, there is still a risk of getting sick.

“When you turn the jets on in the hot tub, you’re aerosolizing the water. In other words, you’re making a mist of the water and putting it into the air,” said Hlavsa. “If those water droplets contain bacteria and they carry that bacteria into the air, if you inhale them, you can become infected.”

Legionella likes warm water, and when chlorine or bromine levels drop, the bacteria can survive and multiply in the slime, called biofilm, that appears on the walls of some hot tubs. Those who are in the hot tub or lounging nearby may want to take caution if they see the slimy substance.

People who are ages 50 and older, have weakened immune systems and/or identify as former smokers should consider not using a hot tub or even sitting near one, the CDC says. Because the amount of water vapor around a hot tub can vary, there isn’t a uniform distance from a hot tub that people with an increased risk for Legionnaires’ disease should maintain. But it should be at least a few feet away, Hlavsa advised.

How long can you stay in a hot tub safely?

Hot tubs have timers for a reason. When the water jets turn off, you should take a break, too. The timer to turn the jets back on is usually placed so that bathers have to get out of the water to reset it. If you see that the time is up, it’s probably a good time to take a break from the warm water. This is especially true for older adults whose ability to regulate their body temperatures is compromised by age.

Editor’s note: This article, originally published June 17, 2021, has been updated.

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Aaron Kassraie writes about issues important to military veterans and their families for AARP. He also serves as a general assignment reporter. Kassraie previously covered U.S. foreign policy as a correspondent for the Kuwait News Agency’s Washington bureau and worked in news gathering for USA Today and Al Jazeera English. 