There is no direct scientific evidence indicating what effect exercise has on acne. However, indirect evidence suggests that, in general, exercise does not make acne worse and in fact may be beneficial. Let's have a look at some of the ways exercise might help with acne-related issues.
Acne lesions are wounds. Wound healing is especially relevant for acne since acne is primarily an inflammatory disease, and inflammation can prevent acne lesions from healing properly. Impaired wound healing can cause pimples to heal more slowly and can make scarring from acne worse.
Here is some indirect evidence from two studies on mice that suggests that exercise might help the body heal more quickly. While results from animal studies often do not predict human results, we can see from these studies that exercise may improve wound healing, at least in some mice.1,2
A 2008 study in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology compared wound healing in both young and old mice that exercised with mice that did not exercise. This study found that exercise reduced inflammation and accelerated the wound healing process in old mice. Interestingly, while the authors found a mild trend toward improved wound healing in young mice, it was only in old mice that this trend became significant. The authors noted, “Our data suggest that exercise accelerates the wound healing process in old mice. This improved healing response in the old mice may be the result of an exercise-induced anti-inflammatory response in the wound.”1
A similar 2012 study in Medicine and Science in Sports and Exercise investigated whether exercise affected wound healing in obese mice or not. This study found that obese mice that exercised displayed increased wound healing compared to those that didn’t exercise. Interestingly, even though obesity is associated with inflammation, this study found that exercise improved wound healing but that the improvement did not appear to be related to a reduction in inflammation. This finding suggests that something else about exercise might provide benefits of wound healing. The authors noted, “Exercise is known to decrease obesity-associated inflammation and has been shown to speed cutaneous wound healing in aged mice...Surprisingly, we were unable to detect any differences in [pro-inflammatory or anti-inflammatory chemicals] in the wounds…This suggests an effect of exercise independent of alterations in inflammation.”2
Oxidative stress refers to an imbalance between free radicals in the skin and antioxidants that combat those free radicals. In other words, there are too many free radicals and not enough antioxidants to neutralize them. Oxidative stress is an important factor in acne since it can bring about inflammation, and acne is by its very nature an inflammatory disease.
In the skin, oxidative stress leads to chronic inflammation, which may lead to acne.3 The anti-inflammatory effects of moderate, regular exercise might help reduce this inflammation, and thus combat acne, by enhancing the natural antioxidant mechanisms that cells use to transform free radicals into harmless molecules. On the other hand, sporadic, intense exercise may actually cause oxidative stress and therefore might increase inflammation.4
So does this mean you should avoid intense exercise? No. It simply means if you wish to engage in intense exercise, you should slowly up the intensity. Let's look at a study that backs this up:
Intensive exercise itself does not appear to increase inflammation, as long as it is regular rather than sporadic. A 1996 study in Medicine and Science in Sports and Exercise found that patients following a 12-week program of progressive strength training exercises did not show any increase in inflammatory immune responses. The authors concluded, “These data suggest that 12 weeks of high-intensity progressive resistance strength training does not affect immune function in young or elderly healthy individuals.”5 These findings indicate that high-intensity exercise does not increase inflammation if done regularly and in a manner that enables people to adjust easily to the level of exercise.
From the evidence we have, sweat not only does not make acne worse, it might even help somewhat.
A 2008 study in Pediatric Dermatology examined the effects of exercise-induced sweat on acne. This study followed 23 adolescent males with truncal acne (acne on the chest and/or back) for two weeks. During the study period, patients exercised hard enough to break a sweat each time for five days per week. This study found no effects of exercise-induced sweat on acne lesion count. In other words, exercising did not worsen or improve acne. The authors noted, “Many patients believe that exercise improves the skin, but some suspect that the associated sweat and dirt exacerbates acne…This small pilot study was not able to show [that exercise-induced sweat has] a significant effect on truncal acne development in physically active boys.”6
While the study mentioned above showed no effect, some evidence indicates that sweat itself may help fight acne. Sweat contains a chemical called dermcidin, which is released constantly from sweat glands. Dermcidin possesses antimicrobial (antibacterial) properties that can kill several types of bacteria, including P. acnes, the bacteria most commonly associated with acne. Some researchers hypothesize that dermcidin helps keep P. acnes populations under control. A 2015 study in Acta Dermato-Venereologica found that dermcidin concentration was significantly lower in acne patients than in people without acne. The authors noted, “This finding suggests that inflammatory acne patients may have a reduced control of the P. acnes population…It is possible that [dermcidin] affects colonization and growth of resident [bacteria]. Sweat mixes with sebum [skin oil] at the openings of pores, where…[dermcidin] and P. acnes may come into contact with each other.”7 This suggests that increased sweat from exercising may enable a larger amount of dermcidin to come into contact with, and therefore help control, P. acnes, which in turn may improve acne.
Exercise has many known health benefits to the body. With respect to acne in particular, regular, moderate exercise may be beneficial by reducing inflammation, promoting wound healing, and reducing oxidative stress. Additionally, sweat induced by exercise contains a chemical called dermicidin which has antibacterial properties that can kill the P. acnes bacteria, which might, in turn, improve acne symptoms.