Red Light Strengthens Skin Barrier (study summary)


Red light-promoted skin barrier recovery: Spatiotemporal evaluation by transepidermal potential

Yuina Abe, Hajime Konno, Shotaro Yoshida, Takeshi Yamauchi, Investigation, Kenshi Yamasaki, Mitsuhiro Denda, Matsuhiko Nishizawa, Michael R. Hamblin

PLoS One
July 10, 2019


The skin responds photochemically to light therapy. Improved mitochondrial function is shown to be a healthy result of light therapy.

Medical and cosmetic practitioners already use light stimulation to treat skin conditions.

Tools such as lasers rejeuvenate skin, remove scars, and speed wound healing.

Certain LED red wavelengths have already been shown to promote skin health, including healing the epidermal barrier.

This barrier is known as the stratum corneum, and it protects the lower skin layer.


  • red light for greater than 10 minutes will improve the epidermal barrier health
  • blue and purple lights will not affect the barrier
  • temperature will not change, eliminating it as a cause for change


Researchers used TEP (transepidermal potential) to measure skin barrier improvement after red light exposure. TEP is a skin barrier health indicator. TEP uses electrical potential differences to determine skin changes.

Researchers disrupted pig belly skin barrier using acetone to remove the lipids.

They irradiated the wounds for one hour.

Exposures included:

  • no exposure (“pristine”)
  • red (600 nm)
  • blue (464-484 nm)
  • purple (403-436 nm)

They measured TEP at these times:

  • after 1 hour of light
  • 1 hour post irradiation

They compared pre- and post-irradition TEP and temperature values.



Subjects’ skin temperature did not change.

TEP values showed that one hour of red light returned the skin barrier to almost-pristine levels.

The control, blue, and purple irradiation groups did not show any TEP recovery values.

The recovery area expanded to as much as 20 mm from the center of the wound.


Researchers studied skin barrier health. The epidermal barrier protects the underlying skin. When this barrier is weak, skin will get damaged.

They found that red light strengthens the dermal barrier. They excluded heat as the mechanism, showing that the red light photons created the positive results.

They found that 600 nm at 40 mW/cm^2 enhanced skin barrier recovery.

Weak irradiance failed to help the skin, even when applied for long exposures.

Blue and purple lights had no effect on skin barrier health

Authors speculate that a calcium wave produced the stronger skin protection mechanisms.



  • no conflicts of interest reported
  • the study validated the measurement method of using electric potential (TEP) as much as it measured skin recovery
  • the poor pigs