In last month’s column, I introduced the idea of treating skin with light. This month, I elaborate on the concept.

Chromophores are molecules that absorb electromagnetic radiation by undergoing an intramolecular electronic transition. Skin cells contain large amounts of nucleic acids and proteins that are UV chromophores. Other chromophores in the skin, such as mitochondrial cytochrome C, endogenous protoporphyrins, melanins, flavoproteins and vitamin B12, absorb visible photons. By doing so, they can cause downstream alterations in skin metabolism that can result in changes in cellular proliferation, differentiation, migration, inflammation or collagen production.

Treating unwanted conditions with electromagnetic radiation is not new technology. PUVA therapy treats psoriasis. Newborns with jaundice are exposed to blue light. In recent years the development of handy technologies and a certain “dislike” of pharmacological interventions have stimulated the research on the effects of the exposure of skin to visible light. 

An LED Primer

A versatile technology to deliver light to the skin consists of Light-Emitting Diodes (LED) that emit electromagnetic wavelengths ranging from 850nm (near Infra-Red or nIR) to about 450nm (Blue). There are LEDs emitting near Infra-Red Radiation (LED-nIR), Red Light (LED-RL), Yellow Light (LED-YL) and Blue Light (LED-BL). The number of PubMed indexed publications a year relative to the use of Light Emitting Diodes was about 100 in the early 2000s. By 2016, the number skyrocketed to more than 1,000.

Authors of comprehensive reviews on the effects of light on skin do sometime conclude their articles by assigning a grade of recommendation for the treatments they have analyzed and reviewed. These grades of recommendations range from A to B, to C, to D…, according to the Oxford Centre for Evidence-based Medicine—Levels of Evidence.¹ Light treatments for acne vulgaris (LED-RL /LED-BL), herpes simplex and zoster (LED-nIR), and acute wound healing (LED-YL) received a grade of recommendation B. The treatment with visible light of other skin conditions received grade of recommendation C or D.

Last month,² I summarized the effects of red light and blue light on acne. This month, I present the effects of yellow light on a few undesirable skin conditions. These results can be found in the scientific literature.^1,3,4,5,6

Yellow Light and Skin

Yellow light has been used to sooth the skin after damaging treatments and to treat psoriasis. Twenty patients were exposed to yellow light immediately after treatment with Erbium-doped fiber laser, a usual treatment to achieve skin resurfacing that is generally followed by intense erythema. After the laser treatment, half the face was treated with yellow light and the other half did not receive yellow light. Exposure to LED-YL improved erythema in 20 out of 20 patients as confirmed by a physician-evaluated reduction in erythema at 24 hours follow-up.³

A similar split face treatment with LED-YL after laser intervention gave similar results.⁴ One report of double-blind, placebo-controlled treatment with yellow light before and after X-ray treatment for all of the duration of the breast cancer radiation therapy did not result in improved radiation dermatitis.⁵

Psoriatic plaques can be cleared by destruction of the dermal papillae. Dilated vessels, the major component of psoriatic dermal papillae, can be selectively destroyed with yellow light lasers. Psoriasis patients were treated with yellow light from a Pulsed Dye Laser and compared with the effects of either antibiotic treatment or triamcinolone ointments.⁶ Seventy percent of the patients receiving either short pulse or long pulse with dye laser had General Score (GS) below 4 at one month. All the patients receiving short pulse, and 87% of the patients receiving the long pulse had GS < 4 at six months. In contrast, at six months only 40% of the patients receiving antibiotic ointments and 13% of the patients receiving triamcinolone had GS < 4.⁶ 

Another group of psoriatic patients with plaques larger than 30cm² was treated with yellow light on half of the plaque every three weeks, and non-treated on the other half. At one month after the end of the treatment, 91% of the treated plaques had a GS lower than 4, whereas only one patient (9%) had a non-treated plaque with GS < 4. And at six months after the end of the treatment, all the treated plaques had GS < 4, and none of the untreated plaques had GS < 4.⁶

Conclusion

Perhaps not all the published papers satisfy the criteria needed to draw conclusions: the systematic search reported by Jagdeo et al identified 4,542 articles relative to skin exposed to LED light. After screening titles, abstracts and full text articles, only 31 original Randomized Controlled Trials using LED blue light (LED-BL), LED red light (LED-RL), LED near-infrared light (LED-nIR) and yellow light (LED-YL) appeared to the authors to be suitable for review. Of these, eight concerned acne vulgaris, three concerned herpes simplex and zoster, six reported about skin rejuvenation, five were about acute wound healing, three dealt with psoriasis, one with atopic dermatitis, two were about chronic wound healing, and one each for oral mucositis, radiation dermatitis and thigh cellulite reduction. 

As I noted last month, red and blue light can be used to efficaciously treating acne. There is the possibility that the patient performs this treatment at home, using appropriate light emitting masks available on the market. This month, we learned that LED-YL can sooth the damage provoked by laser resurfacing or to treat psoriasis, but these treatments must be performed by dermatologists.

References

1. Jagdeo, J., Austin, E., Mamalis, A., Wong, C., Ho, D. and Siegel, D.M. (2018), Light-emitting diodes in dermatology: A systematic review of randomized controlled trials. Lasers Surg. Med., 50: 613-628. https://doi.org/10.1002/lsm.22791
2. Paolo Giacomoni, Treating skin with light (1). Happi Magazine, January 2025 issue.
3. Alster TS, Wanitphakdeedecha R. Improvement of post-fractional laser erythema with light-emitting diode photo-modulation. Dermatol Surg 2009; 35:  813–815
4. Khoury JG, Goldman MP. Use of light-emitting diode photo-modulation to reduce erythema and discomfort after intense pulsed light treatment of photodamage. J Cosmet Dermatol2008; 7: 30–34
5. Fife D, Rayhan DJ, Behnam S, et al. A randomized, controlled, double-blind study of light emitting diode photo-modulation for the prevention of radiation dermatitis in patients with breast cancer. Dermatol Surg 2010; 36: 1921–1927.
6. Zelickson BD et al Clinical and histologic evaluation of psoriatic plaques treated with a flashlamp pulsed dye laser. Journal of the American Academy of Dermatology 1996; 35: 64-68 

Paolo Giacomoni, PhD
Insight Analysis Consulting
paologiac@gmail.com
516-769-6904

Paolo Giacomoni acts as an independent consultant to the skin care industry. He served as Executive Director of Research at Estée Lauder and was Head of the Department of Biology with L’Oréal. He has built a record of achievements through research on DNA damage and metabolic impairment induced by UV radiation as well as on the positive effects of vitamins and antioxidants. He has authored more than 100 peer-reviewed publications and has more than 20 patents. He is presently Head of R&D with L.RAPHAEL—The science of beauty—Geneva, Switzerland.