How Does It Work?
Light therapy refers to non-laser sources of light that help to some degree in preventing papules and pustules, the everyday “pimples” that many people get that are inflamed and red. Smaller lesions, such as non-inflamed whiteheads and blackheads, as well as severe acne lesions like nodules and cysts , respond more poorly. When light is shone on the skin, it penetrates through various skin layers and may help kill some acne bacteria or reduce some of the inflammation or excess sebum (skin oil) production that are characteristic of acne. Benefits of light therapy include low side effects, easy accessibility, and affordability. Drawbacks include incomplete, temporary, and often poor results, and difficulty in application. Even when light therapy does produce results, since light therapy will not clear acne completely, people normally use light therapy in conjunction with other acne therapies, with the exception of isotretinoin (Accutane), which must be used alone.1Light therapy can be administered in a doctor’s office or at home.
When administered in a doctor’s office, more intense light is used, and physicians normally use light devices that can more effectively shine light on a larger area of the skin. One-to-two treatments per week for three-to-four weeks are usually required. Each treatment costs $40 on average. Doctors can also perform a procedure called photodynamic therapy, which involves topically applying a photosensitizer to the skin and “incubating” the skin before light is shone. This tends to produce better results, but also comes with more side effects. You can read more about photodynamic therapy here.
At-home light therapy devices are also available for purchase over-the-counter and usually cost between $200 and $350. Tabletop light therapy devices employ weaker light than devices used at physicians’ offices, and typically require 10-15 minutes of treatment every day, with the user sitting very close to the device. Handheld devices, which some experts claim help light penetrate more deeply into the skin, require a person to hold the device directly on several areas of his/her face and requires a total of 30 minutes to 1 hour of treatment time per day. More recently, light masks that the user wears on his or her face have hit the market as well. Since red light can harm the retina, depending on the device, you may need to wear goggles when administering light therapy. It is important to check manufacturer’s instructions to determine if goggles are required.
What Type of Light Is Used for Acne Therapy?
Different colors of light that are visible to the human eye correspond to different wavelengths. Human eyes can detect light in the range from 400 to 700 nm. The low range of this spectrum (400 nm) corresponds to violet light, whereas the high end of the spectrum (700 nm) corresponds to red light. The wavelength of light determines how deeply light can penetrate the skin, with violet and blue light penetrating only into shallow layers of the skin and red light penetrating into the deepest layers of the skin. Red, blue, or a combination of red and blue light can be used to treat acne. If you are considering using light therapy to treat acne, you should ask your doctor which type of light is best for you.
Blue light has historically been the most commonly used light for the treatment of acne, although doctors now tend to prefer a combination of blue + red light. Blue light covers the spectrum from 407 to 420 nm. When blue light reaches the sebaceous (oil) glands in the skin, it can excite compounds produced by acne bacteria called porphyrins.2-4When excited by light, these porphyrins kill the bacteria.5Researchers are not sure whether blue light works in other ways as well.
Some promising studies have reported that physician-administered blue light therapy results in 60 to 73% reduction in acne, with effects lasting in the weeks following treatment.6-8However, the population size from these studies is too small to conclude just how effective blue light therapy really is and whether it is effective in the long term.
|# of Patients||How Administered||Follow-up After Treatment||Quote|
|30||Twice per week for 5 weeks, duration of each treatment not presented||1 month||Thus, blue light therapy in our study achieved a marked reduction of comedones, papules, pustules, and comedones+papules+pustules by 45.5, 59.3, 46.8, and 51.2% at 3 weeks, as well as by 57.8, 69.3, 73.3, and 64.0% at 5 weeks, respectively. Assessment of efficacy by the investigators showed that 77% of the patients were improved by week 5, while 10% demonstrated ‘unchanged’. By week 5, 40% of the patients showed marked improvement or clearance of their acne lesions.6|
|23||Twice per week for 4 weeks, 15 minutes each treatment||None||Our data show more than an 80% response to 420 nm acne phototherapy with a significant reduction of 59–67% of inflammatory acne lesions after only eight treatments of 15 minutes. Reduction in lesions was steady at follow-up 2, 4 and 8 weeks after the end of therapy. Prolonged remission is evident in the 8 weeks after the end of therapy.7|
|30||Twice per week for 4 weeks, 15 minutes each treatment||2-3 months||The effectiveness was demonstrated by the reduction in the total number of acne lesions as well as the number of acne lesions in grades 3 and 4. Of the nine cases that were followed up to 3 months after the irradiation, six had little new acne, and three had less than five scattered acne lesions.8|
While blue light works by killing acne bacteria, red light penetrates more deeply into the skin and reduces the production of inflammatory molecules that contribute to the formation of acne.9Because red light penetrates into deeper layers of the skin than blue light, it can reach sebaceous glands, and shrink them, ultimately reducing the amount of sebum produced by these glands. Researchers have only performed one small study on 30 people to investigate the effectiveness of physician-administered red light therapy as a stand-alone treatment. The study reported that red light therapy reduced non-inflammatory acne (whiteheads and blackheads) by 59% and inflammatory acne (papules and pustules) by 66%. The authors stated, “Although it does not eradicate the acne lesions completely, it clearly diminishes the number of acne lesions. Patients may require adjunctive treatment to achieve acne-free skin. The effect of treatment is not sustained long term because many patients showed an increase in acne lesions after discontinuation of the use of red light.”10
Blue + Red Light
Most doctors use a combination of red and blue light in order to maximize the benefits of both therapies. Based on two relatively small studies thus far that tested a combination of red and blue physician-administered light, results show a reduction in inflammatory lesions by 76-83%.11-12Although using a combination of blue and red light provided a slight advantage over using blue light only, the difference between the two treatments was not significant.
|# of Patients||How Administered||Follow-up After Treatment||Quote|
|107||Daily for 4 weeks, 15 minutes per treatment, alternating blue and red light||12 weeks||We found a final mean improvement of 76% (95% confidence interval 66-87) in inflammatory lesions using a combined blue-red light radiation…The final mean improvement in comedones was 58% (95% confidence interval 45-71). Again, the combined blue-red light phototherapy did better than the other treatments used but the difference did not reach significant levels.11|
|22||Twice per week for 4 weeks, 20 minutes each treatment, alternating blue and red light||12 weeks||A mean reduction in lesion count was observed at all follow-up points. At the 4-week follow-up, the mean lesion count reduction was significant at 46% (p50.001). At the 12-week follow-up, the mean lesion count reduction was also significant at 81% (p50.001). Comparing the lesion count reduction at the 12-week follow-up between those subjects with mild to moderate acne (Burton grades III and IV) and those with severe acne (Burton grades V and VI), those with a mild to moderate condition showed a mean reduction of 81.3% (p50.01), whilst those with a severe condition exhibited a mean reduction of 82.5% (p50.001).12|
More studies using a larger number of participants are needed to conclusively determine the effectiveness of the commonly used red + blue light combination therapy.
At-home Light Therapy Devices
The studies described above assessed the effectiveness of physician-administered light therapy in doctors’ offices. However, blue, red, and blue + red light devices are also available for at-home use. The advantage of these devices is their convenience, as they can be used at any time without the need to see a doctor. At-home devices use a lower intensity of light and are therefore less effective than devices used in doctors’ offices. At-home devices are also often smaller than the devices used at doctors' offices, and normally expose a smaller area of the skin to the light. Due to individual people using these devices in their own homes, it is difficult to determine how effective they are. One study that evaluated at-home devices reported a 51% reduction in acne after four days of use. The authors concluded that the device was safe for use and effective in reducing acne,13although long-term effects of this therapy were not reported.
The American Academy of Dermatology issued the following statement in 2011 regarding the at-home light therapy devices: "While scientific research substantiates the effectiveness of in-office light treatments, there has been little research performed on many at-home light devices…many of the home-use devices are relatively underpowered and some are not approved for the indications for which they are marketed. Since it is unclear whether these devices are relatively effective or more akin to purchasing ‘hope,’ consumers should discuss their treatment options with a dermatologist to ensure the best results for their individual conditions."13
While blue, red, and blue + red light devices may temporarily reduce acne, they do not completely clear the skin and results are temporary. Therefore, it is best to use light therapy alongside other proven treatments. It is not known whether light therapy devices are effective in the long term. Physician-administered in-office light therapy appears to be more effective than weaker at-home devices, which may or may not be effective at all