4 Illnesses You Can Catch When You Swim

Pools and lakes are often teeming with germs. Learn how to prevent and treat common but often mild illnesses.

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You may have heard stories about people who pick up germs from swimming. But don't panic, swimmers. Most of these recreational water illnesses are mild and easily treated. Educate yourself on the four most common ways swimming can make you sick and what you can do to protect yourself and your family.

Sick After Swimming

You can pick up germs from swimming in a pool, hot tub, lake, ocean, or river. If you swallow, come into contact with, or breathe in mist, there's a chance you can get sick, according to the Centers for Disease Control and Prevention (CDC).

It's important to disinfect pools and hot tubs with chlorine or bromine to prevent the spread of germs. The CDC found that more than 10% of routine inspections at public pools led to immediate closure due to a violation. The following groups of people are more at risk for swimming-related illnesses:

  • Pregnant people
  • People with weakened immune systems
  • Children
  • People who have health problems
  • People who take medication that affects their immune system


Diarrhea is one of the most common swimming-related illnesses. Once the water has been contaminated by germs that cause contagious diarrhea, a swimmer only has to swallow a tiny amount to become infected, according to the CDC. These germs—such as Cryptosporidium, Giardia, Shigella, norovirus, and E. coli—can be transmitted anytime someone who's sick with diarrhea (or has been sick in the last two weeks) enters the water.

Cryptosporidium (crypto for short), the most common cause of pool-related diarrhea outbreaks, can stay alive for days, even in pools appropriately treated with chlorine and other chemicals. That's why public pools require you to shower before taking a dip. To keep the pool safe for everyone, stay out if you've recently been sick.

It may be a good idea to steer clear of swimming in lakes or rivers that aren't monitored for safety. "It all depends on what's coming downstream," said Mindy Benson, nurse practitioner and assistant clinical professor at UCSF Benioff Children's Hospital in Oakland. Animals in the water can also pass on these germs, Benson added. "I wouldn't recommend swimming in backcountry spots you're not familiar with, especially not with children."

Diarrheal illnesses transmitted through the water can last two to three weeks and cause serious, sometimes even life-threatening, dehydration. According to MedlinePlus, call a healthcare provider if you have any of these symptoms:

  • Stools with blood or pus
  • Black stools
  • Diarrhea that lasts two days or more (in adults)
  • Diarrhea that lasts more than 24 hours (in children)
  • Severe abdominal pain
  • Fever
  • Signs of dehydration (such as dry mouth, headache, and infrequent urination, according to MedlinePlus)

Hot-tub Rash

Water that's contaminated with the bacteria Pseudomonas aeruginosa can cause hot-tub rash, a skin irritation, according to the CDC. Germ-killing chemicals like chlorine break down faster in hot water—hence the higher risk posed by hot tubs and the ailment's nickname—but this bug can also be spread in poorly maintained pools or contaminated lakes.

The longer your skin is exposed to contaminated water, the more likely you will get hot-tub rash. "People sometimes think that when they get out of chlorinated water, they're clean," Benson said. "But really, the safest thing to do is shower as soon as you can." You can also ask if the hot tub you're using is checked at least twice a day for proper disinfectant and pH levels or check the water yourself using the pool and hot tub test strips.

Hot-tub rash, which usually appears as itchy, red, bumpy spots or pus-filled blisters, usually goes away on its own in a few days, according to the CDC. If a rash lasts longer than that, call a healthcare provider.

Swimmer's Ear

Otitis externa—or, as it's more commonly known, swimmer's ear—happens when water gets trapped in the outer ear canal, causing bacteria or fungus to grow, according to the CDC. It's more common in kids than adults and can cause itching, pain, and swelling. In some cases, pus may drain from the ear. See a healthcare provider if you think you have a swimmer's ear—you may need antibiotics to treat it.

To protect yourself, dry your ears thoroughly after swimming with a soft towel, Benson said. You can also tilt your head from side to side and pull gently on your earlobe to help water escape, or run a hair dryer on low heat a few inches away from your ears, according to the CDC. Another option? Buy ear drops at the drugstore that can help dry out the ear canal after swimming, but check with a healthcare professional before using them.

Legionnaires' Disease

Germs that live in hot tubs or pools can also infect people who breathe in steam or mist coming off the water. The bacterium Legionella, which causes the lung infection Legionnaires' disease, is sometimes spread this way, according to the CDC.

Legionella is found naturally in water, especially warm water. Making sure that a pool or hot tub is properly cleaned and disinfected—either by asking or by testing it yourself—can reduce your risk of becoming infected, according to the CDC.

According to the CDC, Legionnaires' disease can cause any of the following symptoms:

  • Cough
  • Shortness of breath
  • Chest pain
  • Fever
  • Muscle aches
  • Headaches
  • Diarrhea
  • Nausea
  • Confusion

Legionnaires' disease is usually treatable with antibiotics when diagnosed early, but it can sometimes be fatal, according to the CDC. It's most dangerous to people who are 50 or older, who smoke or have chronic lung disease, or who have weakened immune systems, but everyone should see a healthcare professional if they suspect they've been exposed, according to the CDC.

A Quick Review

It is possible to get sick from swimming in a pool, lake, river, or hot tub. The best way to prevent swimming-related illness is to keep your mouth closed when swimming and dry your ears out after swimming, according to the CDC. And, if you or your child has been sick with diarrhea within the last two weeks, swimming should be avoided. If you follow those steps, you can keep yourself and your child safe while swimming.

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