Chlorine is a chemical disinfectant added to swimming pools to kill germs. In its original gas form, chlorine is a highly irritating and damaging chemical. When added to pool water, chlorine technically turns into the chemicals hypochlorous acid and hypochlorite anion, which disinfect water and is considered safe in the right concentration.
That said, frequent swimmers may find that chlorinated water causes unwanted side effects. When chlorine concentration is too high, it can also cause allergy-like symptoms. Here are five ways chlorine can affect your body.
How Much Chlorine Is Safe?
Adding a chlorine concentration of at least 1 part per million (ppm) to pool water—and 3 ppm in hot tubs—is considered safe by the Centers for Disease Control and Prevention (CDC).
In the U.S., most local health departments require pools to have a combined chlorine level of 0.4 ppm or less. Combined chlorine is chlorine that has already bound itself with germs and waste to disinfect the pool.
It May Cause Dry Skin and Rash
Chlorine and other chemicals in pool water can irritate and dry out the skin. People can’t be allergic to chlorine, but you can be sensitive to the chemical and have skin reactions that are actually irritant dermatitis caused by hypersensitivity to chlorine.
Chlorinated water can cause irritating skin symptoms like:
- Dry, itchy skin
- Red skin
- Hives or rash
- Eczema or psoriasis flare-ups
- Dry skin that triggers acne
Research shows that frequent swimmers are more prone to allergic contact dermatitis or “pool water dermatitis.” This itchy rash is caused by pool chemicals like chlorine. However, some people may get rashes from swim gear like swim caps and goggles rubbing on the skin.
If you have psoriasis, an autoimmune skin disorder that causes thick patches of discolored skin and silver scales, dipping in the pool can further aggravate your psoriasis plaques. Chlorine can also worsen symptoms of eczema, a skin disorder that causes dry and itchy patches of skin.
If your skin is sensitive to chlorine, the American Academy of Dermatology suggests:
- Moisturizing your skin before jumping in the pool
- Rinsing off with warm water after you finish swimming
- Gently patting with a towel to dry off
- Apply moisturizer to damp skin
A Chlorine Rash Might Make Your Skin Feel Itchy After Swimming in a Pool
It May Lead To Lightened and Dry Hair
Chlorinated water dissolves oils that coat and protect your hair, which may make your hair more prone to damage and dryness. Chlorine also breaks down proteins in your hair, increasing your risk of hair breakage. People with white or blonde hair are more at risk because the hair has less melanin (what gives skin and hair color) to protect it.
Chlorine can also lighten your hair, especially if the pool water you swim in has a high concentration of chlorine. (For context, bleach, known to lighten hair and laundry stains, is made with chlorine.) Lightening hair requires high chlorine concentrations, so it takes time and lots of swimming to see the effects. However, UV light from the sun can also lighten hair and increase the impact of chlorine on hair.
To keep your hair healthy while you swim, the AAD suggests you:
- Apply oil or leave-in conditioner to your hair before you swim
- Wear a swim cap to keep hair away from chlorine
- Rinse your hair before swimming to help avoid chlorine absorption
- Rinse and wash your hair after swimming with a shampoo designed to remove chlorine and following up with a deep conditioner
Chlorine Doesn’t Turn Your Hair Green
Oxidized copper is what turns blonde or white hair green after a swim. Copper sulfate is sometimes added to pools to control algae growth. Copper can also leak into the pool from plumbing or copper ionizer equipment. Chlorine corrodes copper that sticks to the hair, resulting in a similar green-blue color of copper patina.
It May Cause Respiratory Issues
High levels of combined chlorine release chloramines into the water and air, which can be highly irritating. Combined chlorine is chlorine that has bound to germs and waste to disinfect the pool.
Chlorinated pools don't usually cause respiratory problems. However, if a pool has built up high levels of chloramines, you can experience respiratory issues like:
- Asthma attack
- Itchy, runny, or stuffy nose
Pools build up chloramines when chlorine mixes with sweat, dirt, poop, pee, and dead skin cells. Even jumping in the pool with deodorant or makeup can create chloramines.
Chloramines also turns into gas around the pool area. A pool that has built up too many chloramines often has a strong chemical smell, which people mistakenly call a "chlorine smell." The chloramines in the air are usually responsible for respiratory issues during or after swimming. This is more common in indoor pools because they are not as well-ventilated to allow chloramine to leave the area.
How Long After Shocking a Pool Is It Safe To Swim?
It May Cause Eye Irritation
Chlorine and other pool chemicals can wash away the thin layer of tears that coat your eyes. As a result, chlorine can cause eye side effects like:
- Watery feeling
- Dry eyes
- Gritty feeling
- Blurry vision
Chloramines released when chlorine combines with human waste also irritate the eyes. Swimmers in a pool with built-up chloramines may experience eye irritation like red, itchy eyes.
The American Academy of Ophthalmology suggests rinsing your eyes with fresh water after swimming to help remove chlorinated water from your eyes. Eye drops may also help rebalance any tears, and wearing goggles keeps chlorinated water out of your eyes.
It May Lead to Yellow Teeth
Chlorine and other pool chemicals can cause people’s teeth to form yellow and brown stains, known as swimmer’s calculus. This staining happens because the pH of chlorinated pools is higher than your saliva, which breaks down proteins that protect teeth from straining and tartar build-up. Chlorinated pools can also erode enamel, which makes you more likely to deal with staining.
However, it's unlikely your teeth will turn yellow after visiting your local pool a few times a week. Research shows competitive swimmers and divers—especially those who spend more than six hours a week in the pool—are more likely to develop yellow teeth.
U.S. Masters Swimming recommends brushing your teeth before swimming to help prevent pool chemicals from building up on plaque. After a swim, rinse your mouth with fresh water or fluoride mouthwash to help restore your mouth's pH levels. Brushing may be too harsh on your enamel after a swim.
A Quick Review
Chlorinated water is considered safe when pools have the correct concentration of chlorine. However, some people are more sensitive to chlorine. Chlorine can irritate the eyes, skin, hair, and teeth.
Occasionally swimming doesn't cause significant side effects, but people who swim frequently are more likely to experience chlorine side effects.
Pools with too high chlorine levels and built-up chloramines can also irritate the respiratory system. If you have issues breathing or have intense allergy-like symptoms, ask the pool manager to check the chlorine levels.