The outermost layer of skin provides an important function called the "barrier function," which means it protects the body from the outside environment and keeps water inside the skin. The layers of cells in the skin barrier and the lipids (fatty acids, ceramides, and cholesterol) that surround them form a strong barrier that protect us from irritants and microorganisms. Extended time in pool water may erode this structure and decrease its protective function. This is important because people with acne tend to already have an impaired barrier function, and this can keep people in a cycle of acne.
There are no direct studies on the effects of pool water on acne-prone skin. However, there are investigations which demonstrate how pool water may impair the skin's barrier function. Therefore, it is important to consider the barrier function when swimming and to help your skin get back to normal after swimming by moisturizing the skin.
To understand how swimming in a pool may affect the skin's barrier and thus acne, let's look at the chemicals that are found in swimming pool water and their effect on the skin. As you read, this may all sound a bit scary, but real-world experience amongst Acne.org members shows us that swimming does not tend to make acne worse. Disinfecting chemicals in pool water may actually help to kill acne bacteria. So don't get too nervous to go swimming. Instead, just make sure to moisturize after swimming if your skin feels dry, stay very gentle with your towel when you're drying off to prevent physical irritation to the skin, and if you can, time your swimming session so you can perform your anti-acne regimen directly after swimming.
Let's start by having a closer look at compounds found in pool water.
Compounds and Chemicals Found in Pool Water
The composition of pool water often changes depending on climate, the number and behavior of people in the pool, and the presence of contaminants. Pool water contains organic matter that mainly comes from swimmers’ bodies, such as urine, sweat, dirt, saliva, body cells, and the personal care products used by the swimmers.1
To remove these substances, pool water is purified by two methods:
- Filtration, which removes particles drifting in the water
- Chemical disinfectants, which destroy microorganisms living in the water
To meet safety standards, any chemical disinfection method must remove 99.99% of what is called an "indicator organism" within 30 seconds of treatment. Chlorine-based chemicals are most often used to achieve this level of disinfection. These chemicals react in water to form hypochlorous acid, which is the actual agent that kills the microorganisms.1
The reaction of chemical disinfectants with organic matter in the water produces a variety of smaller compounds. These compounds are known collectively as “disinfection byproducts,” or DBPs. Some of the most common DBPs are trihalomethanes, nitrates, chlorates, and chloramines. These DBPs, along with chrlorine-based chemicals, may cause damage to the barrier function of the skin, resulting in dryness and irritation.2,3
However, since these chemicals are specifically designed to kill microorganisms, do they also kill acne bacteria, which scientists call P. acnes, and thus help fight acne on some level? This has not yet been studied, but is a possibility.
Dryness of Skin
The most common skin disorder seen in swimmers is excessive dryness of skin, otherwise known as swimmer’s xerosis. Why should people with acne care about having dry skin? Because dry skin represents an impaired barrier function, and people with acne already tend to have impaired barrier function.5This dryness occurs when the outermost layer of skin, called the stratum corneum, becomes stripped of natural oils or otherwise becomes damaged. Pool water can strip away skin oil during an extended period of time in the water, thus damaging the barrier function of the skin.4Applying moisturizer after pool activities helps mitigate the problem. Some people find that applying moisturizer both before and after helps even more.4
Swimmers also shower more frequently than others because they usually shower after they swim. Showers after swimming, in addition to a regular daily shower, may worsen the symptoms of swimmer's xerosis. Let's take a look at a study that shows us how chlorinated water can produce dry skin:
In 2003, researchers studied how different levels of chlorinated water affected skin dryness of patients who had atopic dermatitis, a type of skin inflammation that is itchy, red, and cracked. These patients were compared to healthy individuals who were exposed to the same levels of chlorinated water. Twenty patients and 10 healthy individuals, both groups ranging from infant to adult, participated in the study. The right arm of all participants was immersed in a control bath with negligible amounts of chlorine, and the left arm was immersed in three different concentrations of chlorine, 0.5, 1.0, and 2.0 mg/L (milligrams per liter). Once their arms were dried, the water-holding capacity of the skin was measured immediately, followed by every 30 seconds for 10 minutes. The water-holding capacity of the atopic dermatitis patients was significantly lower after exposure to the 1.0 mg/L and 2.0 mg/L chlorine levels. The participants with healthy skin showed significantly lower water-holding capacity only at the 2.0 mg/L level. The results show that while chlorine dried both healthy and diseased skin, the patients with atopic dermatitis were more sensitive at lower concentrations of chlorine.6This result indicates that acne-affected skin might also be more sensitive to the drying effect of chlorine.
Aquagenic Acne - A Special Case of Acne Affecting Swimmers
Aquagenic acne, a medical term for acne caused by contact with water, is a common skin disorder that affects swimmers. While it has its own name, it really is just common acne, and the treatment is the same. It is simply called aquagenic acne because of how water aggravates the condition. People who normally have clear skin can develop aquagenic acne, or people who already have acne can see a worsening of their acne.4,7
There are two processes that may contribute to the onset of aquagenic acne:
- Sebum (skin oil) overcompensation: The first occurs as the skin oil-producing glands in the skin overreact to loss of skin oil from the top layer of skin during swimming. As the skin oil, called sebum, washes off of the surface, the skin produces more sebum at a higher rate to replace what is lost. Since more sebum usually means more acne, this is one reason why swimming is thought to sometimes cause aquagenic acne.
- Pore-clogging: The second process thought to contribute to the onset of aquagenic acne is clogging of pores. There are a few things that might be at fault. First, the damage that pool water causes to the skin's barrier may cause skin cells to over-produce and clog pores. Second, pore-clogging sunscreens commonly used before, during, or after swimming may contribute to clogged pores.
To prevent aquagenic acne, pay attention to the dryness of your skin after swimming and moisturize if necessary. Also, avoid comedogenic (pore-clogging) sunscreens. Look for sunscreens that are specifically made for "sensitive skin" and sunscreens that print "non-comedogenic" on the label. While this is not a fool-proof way of making sure your sunscreen will not clog pores, it is a step in the right direction.
How Swimming Affects Other Skin Diseases - Does This Give Us Any Clues?
Studies on how pool water and its chemicals affect other skin diseases shows us that pool chemicals may negatively affect the skin, and, in some cases, cause dermatitis, which is an itchy, inflamed, red rash, especially in people who frequently spend time in pool water. Dermatitis is evidence of an unhealthy skin barrier. Remember, anything that disturbs the skin's barrier can potentially be bad for acne.4,7
In a 2015 study, researchers determined that chlorine and several DBPs can cause allergic contact dermatitis.7
In 2010, another group of researchers studied the prevalence of skin symptoms in subjects who worked at 20 indoor swimming pools in Italy. 133 subjects (63 males and 70 females) participated in the study. 16.5% of participants had warts; 15.8% had fungal infections; 9.0% had eczema, and 20.3% had rashes. Lifeguards and trainers, who spend more time in the swimming pool when compared to other personnel, showed higher numbers of skin conditions than the other workers.8
Hydrotherapists, who spend extended time in the pool with their patients, show a higher degree of contact dermatitis.9
A group of researchers from Australia investigated adverse skin and eye effects in school children who swam in three swimming pools, each using a different disinfection system: chlorine, chlorine/ozone, and bromine/ozone. The researchers determined the health effects in the children by sending a questionnaire to the parents. Of the 385 parents who responded to the questionnaire, 104 used the chlorine swimming pool; 66 used the chlorine/ozone swimming pool, and 215 used the bromine/ozone swimming pool. The percentage of children who reported rashes in the 24-hour period after swimming were similar for the chlorine pool and the chlorine/ozone pool: (7.7%) and (7.6%) respectively. Only 4.2% of children who swam in the bromine/ozone pool reported rashes. Most respondents reported a rash on their faces and reported redness and dryness of the skin as the most frequent symptoms. Although the bromine/ozone result is lower, the authors emphasized that there was no statistically significant difference.10
TIP: Perform Your Anti-Acne Regimen After Swimming When You Can
Over-washing the skin is one of the most irritating things you can do to your skin. For people with acne, it's important to wash no more than twice per day. Getting your skin wet in a pool, or getting it wet in any other way for that matter, is tantamount to washing the skin. So, whenever possible, try to time your swimming activities so that you can perform your anti-acne regimen after swimming.
When swimming outside, you are likely exposing your skin to sunlight. Sunlight is not all bad. It promotes the synthesis of vitamin D in our bodies, which is beneficial to skin health, and may be beneficial for acne. On the other hand, over-exposure to the sun can damage the skin and bite back with acne in the weeks following exposure. A little bit of sun is ok, but make sure to avoid sunburn.
Important: When choosing a sunscreen, make sure you choose a "broad-spectrum" and "non-comedogenic" option. Look for terms like "for sensitive skin" or "for acne-prone skin" when you can find it. And when applying sunscreen, like with any other topical skin care product, use your bare hands and stay gentle while applying to avoid physically irritating your skin.
Swimming in a pool is relatively safe when proper precautions are taken, such as moisturizing, staying gentle when drying, avoiding over-washing after swimming, and guarding against too much sun exposure with sunscreens that do not clog pores.