How can chlorine damage your eyes?

13 June 2019

Author: Kate Green

Chlorine damage eyes causing conjunctivitis, pink eye

Understanding the impact of chlorine

The summer holidays are fast approaching and, for many people, this means a trip away. Whether it’s Butlins or Bali, it’s likely that you’ll be taking a dip in the pool to relax. A lot of people talk about the effects of pool chlorine on their hair, skin and nails – lots of dryness all round – but not everyone understands the long term impact on your eyes. You might wear goggles to prevent the redness that usually comes with swimming, but do you know what chlorine actually does to your cornea and overall eye health?


Your eyes have tear film on the cornea which acts as a protective barrier from dirt and germs. Unfortunately, there is plenty of bacteria in water and, while chlorine is put into swimming pools to kill germs, it also strips away the tear film on your eye, making your eyes more vulnerable to infection. The most common eye-related problems caused by chlorinated water are:

- Conjunctivitis – This infection can either be bacterial or viral and thrives in water. It causes irritated, itchy eyes, severe redness and crusting.

- Red eyes – Chlorine dehydrates your eyes and, as mentioned above, removes the tear film. This results in blurriness and occasionally distorted vision, but it’s usually only temporary. The redness occurs when the blood vessels near the surface of your eye become larger and then dilate.

- Acanthamoebic keratitis – An amoeba is a single cell organism which either lives in water or as a parasite, meaning that swimming pools are an ideal spot for them to spread. If you swim with contact lenses in, you’re at risk of catching acanthamoebic keratitis, as the bacteria can become trapped between your cornea and contact lens. This can lead to corneal ulcers, permanently damaging your vision and causing severe infection. In the worst cases, patients even need corneal transplants to help restore their vision.


It goes without saying that you must never wear contact lenses in the water, but there are other steps you can take to reduce your risk of developing the conditions listed above. Invest in some lubricating eye drops to help restore your cornea’s tear film quickly after your dip in the chlorine. These will also help with any dryness, redness and irritation you experience. Above all, wear water tight goggles if you’re submerging your head in the pool. This will save you from most of the negative eye-related problems that come with swimming!


The science behind chlorine


The main reason for your eye irritation after swimming is down to chlorine’s pH level. Water’s normal pH level is 7 (neutral); below 7 indicates a more acidic level, and values above 7 suggest alkaline levels. The pool water’s pH should be between 7.2 and 7.8 to be safe for swimmers to use, while also ensuring that bacteria levels are kept low. Ideally, chlorine in the pool would have a pH of 6.5 as this is when it’s 100% effective against bacteria. However, 6.5 is far too acidic for our skin, which is why the recommended level is between 7.2-7.8. At this less acidic level, the chlorine doesn’t break down the germs, fats and oils in the water as effectively, which is how bacteria and infections still remain in the water. It is the partially broken-down compounds which cause irritation to eyes as the chlorine can’t work properly. Similarly, itchy eyes can also happen when there is too much chlorine in the water – it’s all about finding the perfect balance.


Saltwater is often touted as a “more natural approach” than chlorinated water, as it’s “safe on skin, hair, and your eyes”. Saltwater pools rely on salt to keep them clean, instead of utilising chlorine tablets or other stronger chemicals. Chlorine is actually a by-product of salt so, even if a pool is just saltwater, there will still be small amounts of chlorine in it. While chlorine is known to cause some swelling in the eye’s cornea, saltwater doesn’t have the same effect. This is because the concentration of water in your eyes is actually very similar to sea water, and so is much gentler on your eyes than chemicals such as chlorine.


While you’re away this summer, invest in some goggles for when you fancy a dip in the pool. Failing that, some saline eye drops should help calm any eye irritation and redness, as well as flush out infections. Above all, remember to take your contacts out before getting into the pool, as water harbours all kinds of infections and bugs. Ultimately, chlorine probably won’t make you go blind, but repeatedly exposing your cornea to chlorine, especially for long periods of time, is never a good thing and should be avoided where possible.

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