Efficacy of blue light vs. red light in the treatment of psoriasis: a double-blind, randomized comparative study

J Eur Acad Dermatol Venereol. 2012 Feb;26(2):219-25. doi: 10.1111/j.1468-3083.2011.04039.x. Epub 2011 Mar 24.


Background: Protoporphyrin IX is present in psoriatic skin without the preceding application of aminolevulinic acid. Therefore, endogenous photosensitizers in psoriasis are a potential target for photodynamic treatment with high-dose visible light.

Objectives: In the present pilot study, treatment with high-dose blue and red light in psoriasis were analysed with respect to clinical improvement and potential side-effects.

Methods: In 20 patients, two stable psoriatic plaques were treated with either blue or red light, three times weekly for four consecutive weeks. To remove scaling that could potentially interfere with penetration of the light into the skin, daily application of 10% salicylic acid in petrolatum was started at the screening visit and continued until the end of the study.

Results: Clinical improvement was seen after treatment with blue as well as after treatment with red light. With respect to scaling and induration, no major differences between both light sources were seen. Improvement of erythema, however, continued in blue light irradiated plaques throughout the whole study period, whereas after red light no significant improvement was seen after six illuminations.

Conclusions: The clinical improvement of psoriasis, with respect to erythema, in particular after blue light and to a lesser extent after red light indicates that visible light treatment could represent a treatment option for psoriasis.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Double-Blind Method
  • Female
  • Humans
  • Light*
  • Male
  • Middle Aged
  • Phototherapy / adverse effects
  • Psoriasis / radiotherapy*