wash their skin with hot or cold water and which is better for acne. Let's take a look at the available evidence. From what you'll see, it is probably best to avoid very hot water when washing but warm or cool water is most likely fine.
A few isolated studies suggest exposing the skin to heat above 42°C (107.6° F) has effects such as drying the skin, increasing sebum (skin oil) excretion, and causing changes to the skin that are similar to those that happen when the skin ages. All of this leads us to believe that washing with hot water is most likely not ideal. However, one study showed that warmer temperatures (but not hot) might improve skin healing. In other words, while it is probably best to avoid hot water, warm water is likely safe.
When it comes to cold water, we have no studies looking at the effects of cold-water washing on acne or skin health, but we do know that ice is dramatically anti-inflammatory and may help heal acne. Would cold water do the same? Probably not to the same degree, but it probably also wouldn’t hurt. We need more studies before we can draw any conclusions on cold or cool water, but washing with either is likely safe.
The bottom line: Washing with warm water that does not scald or burn the skin is a good and safe idea. If you prefer to wash with cold water, or do a cold rinse after washing with warm water, feel free.
The Science: Hotter Temperatures
One study suggests warm temperatures may promote skin barrier healing and actually be beneficial for the skin. This is important because damaging the skin's barrier may be detrimental for acne. However, isolated studies show that hot temperatures may cause skin dryness, sebum buildup, increased topical drug absorption, and perhaps skin damage and wrinkling. Let's have a look at this mixed bag.
One thing we know for certain is that hot water can strip the skin of oils that are essential for protecting and hydrating the skin. If these oils are not replaced, the skin becomes dry and itchy. In a review in Nutrition Reviews, the authors wrote, “Skin dryness is usually associated with exposure to dry air, prolonged contact with hot water and scrubbing with soap (both strip oils from the skin).”1
In 1976, a review in British Journal of Dermatology reported that hot water caused swelling of the skin cells lining the pore, which narrowed the diameter of the pore, making it difficult for sebum to escape onto the surface of the skin. This resulted in pores being clogged. Because acne is caused by an initial clogged pore, this is something which could hypothetically be a concern. However, the temporary narrowing of a pore caused by heat is reversible and is likely not a concern when it comes to clogged pores. The same report stated that sebum excretion increased 10-fold for every 1°C (1 degree Celsius) rise in air temperature. That is, warmer temperatures caused existing sebum to drain out of the pores more easily than cooler temperatures.2This shouldn’t be of concern either since draining/excretion of sebum isn’t necessarily a factor in acne development. Rather, sebum production is. In spite of all of this, the important thing to note when it comes to washing with warm/hot water is that water of this temperature can damage the skin barrier, which makes the skin more susceptible to acne.
Increased Absorption of Topical Drugs
If you are taking topical acne medications, applying them when your face is warm, such as after washing with warm water, could potentially increase their absorption. This could be potentially beneficial since topical acne treatments must penetrate to work. In a 2015 review published in the Journal of Controlled Release, scientists reported enhanced absorption of topical drugs when skin was warmed to 30 °C (86°F) and higher.3The reason is not understood. The scientists hypothesized that changes in the skin barrier and increased blood flow to the skin were responsible. The skin’s lipids (fats) are an important part of its barrier. When the skin’s outer layer becomes hydrated, the lipids in the skin become liquid-like. Warmer temperatures further increase lipid fluidity. When there is more blood flowing to the skin, it becomes warmer. Higher temperatures cause the blood vessels in the skin to dilate, or widen in diameter, which allows more blood to flow to the skin. Lower temperatures cause the blood vessels to constrict, or shrink in diameter, inhibiting blood flow to the skin.4
Skin Damage and Wrinkling
A healthy skin barrier defends the skin against foreign particles and bacteria and helps prevent water loss. There is evidence that people with acne have a compromised skin barrier.5A 2009 study published in the Journal of Investigative Dermatology Symposium Proceedings found that exposure to 43°C (109.4°F) heat for 90 minutes caused changes to the skin that were similar to those caused by too much sun exposure, such as premature wrinkling and skin-cell damage. Their results revealed that prolonged exposure to 43°C heat can cause oxidative stress, which means that the levels of certain molecules in the skin can cause damage to cell structures and DNA (genes). They also found that prolonged exposure to heat released molecules that can negatively affect the strength and structure of the skin.6To keep acne at bay, it is best to maintain a healthy and balanced skin barrier.
A 2007 study published in Journal of Investigative Dermatology found that applying heat between 36°C and 40°C (96.8°F and 104°F) actually helped the skin barrier recover from damage faster. However, temperatures above 40°C delayed skin barrier recovery. The authors hypothesized that these effects were due to the presence of molecules called neurotransmitters in the skin.5Neurotransmitters help the body and brain communicate with one another, and they can influence the skin’s response to stresses, such as extremes in temperature.
You may have noticed that your fingers wrinkle up like raisins when exposed to water for a long period of time. This effect is temporary and reversible. According to a 1997 study published in The Journal of Hand Surgery, warmer water caused this temporary wrinkling to accelerate. Participants in this study submerged their hands into buckets of water at temperatures ranging from 20°C to 45°C (68°F to 113°F). The shortest time it took for hands to wrinkle was 3.8 minutes in 45°C water, and the longest it took was 8.7 minutes in 20°C water. As far as we know, these effects are completely reversible. However, it is possible, yet not probable, that repeated wrinkling might accelerate permanent wrinkling of the skin over time.7Since facial skin does not wrinkle like skin on hands after prolonged exposure to water, this is probably not something to worry about.
While there are no studies examining the effects of cold or cool water when applied to the skin, cold temperatures can reduce swelling and inflammation,8,9and many acne sufferers report that treating acne lesions with ice helps reduce swelling. Cryosurgery, the practice of removing a lesion by freezing it off, can successfully treat acne lesions and acne scars.10Cryotherapy, the well-known practice of applying cold to an injury site like a sprained ankle, effectively reduces swelling and inflammation. However, cryotherapy is effective only once the skin temperature is reduced all the way down to 10°C to 15°C (50°F to 59°F).9This can take 10–20 minutes on major joints of the body but happens more quickly on the surface areas of the face, in as little as 5 minutes. Still, that is far more time than anyone takes washing their skin, and cold water from the faucet is much warmer than the cold that is used in cryotherapy, like ice for example.
One study shows that cryotherapy might also help reduce sebum production, which could help acne sufferers since most people who have acne have an increased level of sebum production:
A 2015 study published in the Journal of Investigative Dermatology showed that cryotherapy also reduced the number of sebocytes (skin oil cells) and total sebum production. A single treatment of -10°C (14°F) for 20 minutes reduced sebum production by 20% for 2 weeks.11
However, again, washing with cool or cold water for only a few seconds is highly unlikely to have the same effect.
So, when it comes to cool temperatures, we know that icing an acne lesion can help heal it more quickly, but whether washing with cool water for only a few seconds would approximate anything close to the application of ice or not is unlikely.
Right now, there is not enough information to advocate for washing with warmer or cooler water. However, washing in hot water may cause damage to the skin over time and could disrupt the important skin barrier. Ice can reduce swelling, inflammation, and sebum production, but cold tap water is unlikely to achieve the same effects. If you wash with warm water, feel free to continue. If you prefer cold, that’s fine too.