Michael R. Hamblin, Professor of the famous Harvard Medical School in Boston, says in a recent publication [1]: “Infrared-A appears to be the solution, not the problem. It does more good than bad for the skin.” This is especially true when the skin is exposed to the appropriate irradiance and dose of infrared-A (near infrared NIR) similar to daily sun exposure received by people in real life. Specific protection against the Sun’s infrared-A is therefore unnecessary. As far as ultraviolet radiation is concerned, an adequate protection is still required.

The recent publication confirms the content of a press release of the “Association of the Scientific Medical Societies of Germany” in 2010 [2].
Hamblin describes that in publications claiming to show the dangers of the infrared-A component of the Sun’s radiation irradiances were used which were up to the 100-fold of the mean infrared-A irradiance of the Sun during the day in the tropics. Effects depend not only on the dose of irradiation, but also on the irradiance level. Effects seen following short exposures to very high irradiances can not be interpreted as suggesting that the same result will occur if irradiation (heat supply) is carried out over a longer period of time using a lower irradiance level.

A specific effect of infrared-A exposure which was independent of a pure temperature increase could not be identified as the reason for effects interpreted as being undesirable: Instead, Hamblin describes that concerning water-filtered infrared-A (wIRA) even with an irradiance of more than fivefold of the maximum possible irradiance of the Sun’s infrared-A on the surface of the Earth with the skin temperature maintained at 37 °C by convective cooling from air ventilation no significant changes of cell viability, inflammatory status, free radical content, or the antioxidant defense systems of the skin were found [3]. Conversely, after convective heating to about 45 °C and without any irradiation at all, free radical formation was almost doubled and antioxidant power was reduced to about 50%. This means that not the irradiation is the problem, but the reached tissue temperature is the limiting factor.

Beyond this, the publication of Hamblin lays the focus on the beneficial effects of infrared-A (“photobiomodulation”):
In a series of studies infrared-A has been shown to provide some protection against undesirable effects of the Sun’s ultraviolet radiation: the Sun’s infrared-A in the morning can be interpreted as preparing the skin (“photoprevention”, “preconditioning”) for the UV burden at noon and the Sun’s infrared-A in late afternoon as repair phase. In addition low irradiances and doses of infrared-A have beneficial effects on collagen metabolism.

Concerning working mechanisms of infrared-A detailed conceptions about signal cascades exist, which are triggered by cytochrome c oxidase as photo acceptor in the mitochondria of cells and which lead to a promotion of cellular defense mechanisms. Concerning the Sun’s spectrum reaching the surface of the Earth photopreventive wavelengths are described between 630 and 940 nm (visual red light and infrared-A).
Summarizing, a specific protection against the Sun’s infrared-A is unnecessary. On the contrary the Sun’s infrared-A (in any case with relatively low irradiances and irradiation doses) as well as infrared-A in healthcare – there with adequately moderate chosen irradiances and irradiation doses – can be used reasonably for humans.

Publications:
[1] Barolet D, Christiaens F, Hamblin MR. Infrared and skin: Friend or foe. J. Photochem. Photobiol. B 2016; 155: 78–85. DOI: 10.1016/j.jphotobiol.2015.12.014
[2] Müller W: The Sun’s infrared-A is not detrimental to the skin. Press release of the “Association of the Scientific Medical Societies of Germany” in “Informationsdienst Wissenschaft idw”, published on July 15th, 2010. Online available from: https://idw-online.de/en/news379479 (English version of the press release).
[3] Piazena H, Pittermann W, Müller W, Jung K, Kelleher DK, Herrling T, Meffert P, Uebelhack R, Kietzmann M. Effects of water-filtered infrared-A and of heat on cell death, inflammation, antioxidative potential and of free radical formation in viable skin – First results. J. Photochem. Photobiol. B 2014, 138: 347–354. http://dx.doi.org/10.1016/j.jphotobiol.2014.06.007

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