- The Sun’s Effect on Acne Is Still an Open Question
- The Effect of Artificial Light on Acne
- Vitamin D and Acne
- Light & Laser Treatment for Acne - Does This Give Us Any Clues?
- Potential Side of Effects of Sun Exposure
- The Bottom Line
The Sun’s Effect on Acne Is Still an Open Question
There is limited and conflicting scientific evidence to support the use of sunlight in treating acne. In fact, partly due to the fact that it is difficult to perform studies on sun exposure, there are no reliable studies that look directly at the effect of sunlight on acne.
For this reason, to get an approximate answer to the question of whether the sun helps or hurts acne we need to look at two other types of studies that can potentially shine light (no pun intended) on this question:
- Studies using artificial light on acne: Because some days are cloudier while other days are sunnier, this makes it hard to control for sun exposure in studies. For this reason, scientists will often instead opt for artificial light sources like sun lamps which can be shone on the skin at exact wavelengths and for exact amounts of time. These studies indicate that some light wavelengths might have a beneficial effect on acne while other studies indicate the opposite.
- Studies looking at seasonal variations in acne: There are also several studies that examine seasonal variations in acne, which could show us whether acne tends to improve or worsen in the summer, when people get more sun exposure, but these studies also produce conflicting evidence.
Let's look more closely at these two types of studies one by one, starting with studies using artificial light.
The Effect of Artificial Light on Acne
Studying the effects of sunlight can be fraught with error because depending on cloud cover, latitude, season, and time of day, sun exposure can vary greatly. Therefore, scientists have resorted to artificial light in their experiments, while fully admitting that artificial light may not be directly generalizable to natural sunlight.1 In other words, we cannot necessarily say that natural sunlight will have the same effects as artificial light, but at least it gives us a clue.
Unfortunately, an analysis of the research, published in the journal Family Practice, points toward conflicting and weak evidence on artificial light and acne, so the jury is very much still out when it comes to the effects of artificial light on acne.
According to several of the reviewed studies in the analysis, “Trials of artificial UV-B, UV-A and combined light sources, and phototherapy with artificial blue-red, blue, violet, green and full-spectrum light sources have been found to improve acne.” However, the authors noted that these studies had methodological problems that limit the ability to interpret their results.
In contrast to the other studies reviewed in the meta-analysis, a trial of UV (ultraviolet) light applied to rabbit ears resulted in an increased tendency for sebum (skin oil) to form acne comedones. Rabbit ears are the closest animal model to human skin. This result suggests that light might cause pores to become clogged and make acne worse.1
The Effect of Seasonal Variations on Acne
The sun produces different levels of intensity during different seasons. Would seasonal differences in acne tell us whether the sun helps or hurts with acne, for instance when the sun is highest in the sky in the summer?
Several studies have analyzed seasonal variations in acne severity and have again reached conflicting conclusions, with the majority showing improvement of acne during summer months, but some others pointing toward a worsening of acne in the summer. Also, many of these studies use self-reported data, which is unreliable. Therefore, due to the conflicting results and less than ideal study methodology, we cannot draw conclusions from them.
According to a 1989 study in the journal Photodermatology, in which the authors examined and interviewed 809 randomly selected people from four different Swedish cities, “The majority of subjects with atopic eczema, acne vulgaris or seborrheic dermatitis experienced improvement after exposure to sunlight.”2
A 1996 study in the International Journal of Dermatology found no effect of season-dependent sun exposure on acne severity. The authors asked 139 patients whether their acne worsened during summer or during winter, whether their acne improved seasonally, and whether they noticed any change at all with different seasons. This study states, “About one-third of the patients reported an aggravation of their acne in winter, but also approximately one-third of the patients complained about an aggravation of their acne in summer. Another third did not notice any change.”3
A 2002 study in The Journal of Dermatology asked 452 patients about seasonal variations in their acne. This study found that about half of patients noticed seasonal variations: the majority of these (56.33%) noted that their acne was worse in summer; 16% improved in summer, and only 11.35% said their acne was worse in winter. The authors commented, “Significantly, a majority (80.62%) of patients noticed a summer aggravation due to sweating and increased humidity.”4The authors noted that their results contradicted other studies that indicate improvement in the summer and worsening in the winter, and they proposed that the increased temperature, humidity, and sweating in their region might account for the majority of patients whose acne worsened in the summer in this study.
A more recent small study from 2015, in the Journal of Drugs in Dermatology, compared the facial skin of 17 adolescent males with and without acne over the course of one year. This study found that “[Skin oil] production was significantly greater in subjects with acne than in those without for each season examined…and was lowest in the winter and highest in the fall.”5
Another 2015 study in the Journal of the American Academy of Dermatology collected data for 9301 acne patients, 73% of whom were female. This study found that acne cleared in the fall and worsened in the winter. In addition, analysis of 6101 patients who were seen multiple times indicated a “significant trend of summer clearing…and winter worsening.” The authors suggested that summer improvement may be attributed to the known immune-regulating and antibacterial effects of the sun. Ultraviolet light, which suppresses the immune system and decreases inflammation, may be the cause of the summer/fall improvement in acne.6
Vitamin D and Acne
Vitamin D is an extremely important vitamin for overall health and health of the skin. There is a correlation that shows that people with acne tend to have lower levels of vitamin D in the blood, and there is some evidence that vitamin D can help in the treatment of acne. Since exposure to sunlight is the only way that the body produces vitamin D, it is reasonable to infer that sun exposure might help improve acne for this reason.
So does sun exposure allow us to achieve adequate vitamin D levels, and thus reduce acne? This is a possibility, but once again, the evidence we have on vitamin D and acne is limited and preliminary, so this branch of research does not get us closer to an answer whether the sun helps or hurts acne.
A 2011 article in Dermato-Endocrinology notes that vitamin D has antimicrobial (anti-bacterial) effects, and that vitamin D deficiency has negative effects on general well-being. The authors state, “Vitamin D and its analogues…are playing an increasing role in the management of [skin conditions such as] atopic dermatitis, psoriasis, vitiligo, acne and rosacea.” The article states also, “Vitamin D constitutes an inexpensive [preventive] option and possibly therapeutic product either by itself or as a synergistic agent to traditional antimicrobial agents.”7
According to a 2013 study in the Indian Journal of Dermatology, sebocytes (skin oil cells) treated in vitro (in the lab) with vitamin D caused these cells to decrease their production of proteins that contribute to inflammation.8
A small 2014 study in Dermato-Endocrinology compared blood levels of vitamin D in patients with nodulocystic (severe) acne with those of healthy controls. This study declares, “The patients with nodulocystic acne had relatively low serum vitamin D levels compared with the subjects in the control group. The findings from this study suggest that there is a connection between low vitamin D levels and acne.”9
How to Get the Right Amount of Vitamin D
Regardless of whether getting sun exposure will allow you to improve your acne, it is important to get the vitamin D you need for your overall health. Vitamin D deficiency is pervasive in modern society due to restricted time in the sun and the use of sunscreens. Therefore, if blood vitamin D levels are low, doctors recommended spending time in the sun However, the amount of sun required varies according to several factors, including:
- Skin pigmentation (light or dark)
- The amount of exposed skin
Because of these variations, the amount of sun exposure a given individual might need varies. For instance, closer to the equator, people need less sun exposure than they would the further they get from the equator. Also, people need far more sun exposure during winter months to achieve the same amount of vitamin D they would get during summer months. Using common sense is often best. Get a little sun when you can, but limit your sun exposure so that you do not get burnt.10-11
Light & Laser Treatment for Acne - Does This Give Us Any Clues?
Even given the lack of scientific evidence that sunlight can help acne, there are several existing light-based treatments that operate on the principle that light is beneficial for acne. These treatments, which rely on the antimicrobial and anti-inflammatory properties of several wavelengths of light, usually are somewhat effective. Whether the sun would offer similar benefits is unknown, but because light and laser therapy do help reduce acne to some degree, it is possible that the sun's rays could do the same.
A 2013 study in the Indian Journal of Dermatology, Venereology, and Leprology notes, “A variety of light and laser devices has been used for the treatment of acne,” and that these devices appear to work by targeting underlying mechanisms that contribute to acne, such as by eliminating bacteria, reducing sebum production, and reducing inflammation.12
According to a 2013 article in Drug Resistance Updates, blue light has antimicrobial effects that can kill P. acnes (acne bacteria) with fewer side effects than those of ultraviolet light. The authors noted, “Blue light therapy is a clinically accepted approach for Propionibacterium acnes infections.”13
A 2011 study in the Annals of Dermatology demonstrated that photodynamic therapy, a common treatment for acne that involves putting a substance on the skin that increases photosensitivity and then exposing the skin to light, is effective in reducing acne lesions. This study used photodynamic therapy on 12 patients with mild to moderate acne. The authors found a “significant reduction in the number of inflammatory acne lesions after [photodynamic therapy].” They also found a significant decrease in sebum production after 2 weeks and a reduction in the expression of receptors that contribute to inflammation in skin oil–glands.14
Potential Side of Effects of Sun Exposure
A moderate amount of sun exposure may or may not help acne symptoms. A sunburn, on the other hand, is skin damage and will very likely result in a breakout in the week or two following the sunburn. To decrease the chance of developing acne, avoid sunburn.
Long-term overexposure to sunlight also results in serious side effects such as increased risk of melanoma and non-melanoma skin cancers. In addition, commonly used acne medications, such as tetracycline antibiotics and isotretinoin (Accutane), can cause the skin to become more sensitive to the sun: this increases the risk of sunburn and, subsequently, cancer development.1
The Bottom Line
Thus far, research has been unable to positively prove or disprove that sun exposure is effective as an acne treatment. However, there is evidence that there is a correlation between low levels of vitamin D and acne, suggesting that sun exposure could help acne for this reason. Light and laser therapy have also been shown to be at least somewhat effective in reducing acne lesions. However, if you choose to get regular sun exposure, be cautious. Too much sun will cause sunburn, which will bite back with acne in the weeks following the sunburn. And too much sun can also cause skin cancer over the long haul.