Ask a doctor: Is it safer to swim in a lake or a pool?

We’re lucky here in the Pacific Northwest to have so many options for a swim on a hot day — community swimming pools, fresh lakes and rivers, Puget Sound waterfronts, and family-friendly water parks.

Before jumping into the deep end, though, safety comes first. Lifejackets, swim lessons and parental supervision are the obvious precautions, but what about your immune system? Bodies of water, regardless of their source, have the potential to carry bacteria, viruses and parasites that could get you sick.

To help you make the safest choice, our experts compare the risks between pools and lakes and share their best tips to stay healthy no matter which you choose.

The quick answer

Pool and lake water each present their own infection risks. Your safety will ultimately depend on the water quality, which is easier to control in a pool.

Lakes have their own unique risks through environmental contamination that can’t be controlled like it can in pools. Proper pool maintenance and chlorination can keep you better protected from bacteria and infectious pathogens.

Take a deeper look

Pools present the risk of a range of infectious diseases, including:

• Gastrointestinal pathogens
• Outbreaks of chlorine-resistant parasitic infections
• Legionella bacteria, which develops and grows in warm bodies of water, such as a stagnant pool in direct sun

Hot tubs can also grow specific bacteria that infects hair follicles and causes a condition referred to as hot tub rash.

While it can be challenging to identify risk by simply looking at a pool, there are a few things to watch for. If the pool looks dirty, unmaintained, or there’s any sort of discoloration or buildup on the surface, stay out. When in doubt, ask the pool owner about their maintenance and chlorination process.

Lake water carries many of the same bacterial risks as pools, as well as other environmentally driven ones. E. coli and shigella can infect the intestines, and microscopic parasites that burrow into the skin can increase your risk for swimmer’s itch. And while much rarer, a freshwater amoeba called Naegleria fowleri can result in a fatal brain infection.

Knowing there’s no way to control natural bodies of water, using visual indicators and checking with your local parks and recreation department for safety warnings will be your best bet for safe swimming.

If the water looks stagnant, has visible algae blooms or fecal matter, or is unseasonably warm, stay out. Be especially wary if it has recently rained. Runoff from animals and sewage treatment plants increases with heavy rain.

Even with all this knowledge, developing safe swimming habits is key in case you unknowingly find yourself in contaminated water: Shower before and after every swim and avoid submerging your nose for long periods of time. Be especially vigilant of young kids who are more likely to swallow water or play in shallow water, where contamination risk is higher. Consider talking with your doctor or other health care provider about the rotavirus vaccine if your children are frequent swimmers.

When to seek care

Most people will likely show symptoms within 24 to 72 hours of exposure. However, some symptoms may appear sooner or later depending on the specific bacteria. Norovirus is notably quicker to cause symptoms, typically within a day.

Look for symptoms such as nausea, vomiting, diarrhea or skin irritation, like itchiness or minor rashes. These symptoms should last no more than a few days when treated with over-the-counter medication or ointments.

Go to your nearest urgent care if you or your child experience symptoms such as high fever, severe abdominal pain, blood in the stool or an inability to eat or drink.

Medical review provided by Christina Schofield, MD, an infectious disease provider at MultiCare Capital Medical Center. Note: This information does not qualify as individualized medical advice. Please schedule an appointment with your care team to ensure the most appropriate care.