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Water-filtered Infrared-A (wIRA) is not Implicated in Cellular Degeneration of Human Skin

20.11.2007 - (idw) Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften

In accordance with previous investigations water-filtered infrared-A (wIRA) at appropriate irradiances is unlike ultraviolet-A not implicated in photoaging of the skin. wIRA, which reaches the surface of the earth in moderate climatic zones as heat radiation of the sun and which is used therapeutically in wIRA radiators, could even be implicated in a protective manner. In an original publication in the internationally oriented interdisciplinary medical e-Journal "German Medical Science" of the Association of the Scientific Medical Societies in Germany (AWMF) investigations of human skin fibroblasts after single exposures between 15 minutes and 8 hours to wIRA or 15-45 minutes to ultraviolet-A (UV-A) at two physiologic temperatures as well as after repeated exposures with wIRA are presented: Single exposure of cultured human dermal fibroblasts to UV-A yielded a very high increase in MMP-1 mRNA expression (11-fold expression for conventional Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and 76-fold expression for quantitative real-time RT-PCR) and a dose-dependent decrease in cell survival. In contrast, even at the investigated disproportionally high irradiance wIRA did not produce cell death and did not induce an increase in MMP-1 mRNA expression detectable with the sensitive methods applied. Additionally, repeated exposure to wIRA did not induce MMP-1 mRNA expression.

The results of the present paper, in which particularly a great effort to avoid any temperature alteration of the cells was undertaken, are consistent with publications of several working groups and contradict publications primarily of one working group, which described undesired effects of infrared-A and wIRA in cell cultures.

Reasons for the different results are presented in detail in the now published paper: so the paper published now used normal skin fibroblasts and not foreskin fibroblasts of the newborn child which are well known to behave differently and are not representative of human skin. Effects on cells depend not only on the irradiation dose but also on the irradiance. In some other publications it was not taken into account that cell cultures, which represent a monolayer of cells and which have in contrast to human skin no horny layer and no heat distribution by blood circulation, cannot be irradiated with the same irradiance as a living skin: corresponding to this partly the three- to tenfold of a physiologic irradiance was used in cell cultures. In the present paper with careful and effortful temperature fixing of the cells, which prevented an overheating of the cells, no undesired effects were seen even at the investigated disproportionally high irradiance. Such a temperature fixing is important to avoid misinterpretations, as MMP-1 mRNA, whose increase is interpreted partly as an indication for skin aging, shows an increased expression already by temperature increase about a threshold - independent from the cause of the temperature increase and thus also independent from specific qualities of infrared. Appropriate therapeutic irradiances of wIRA - which can be used therapeutically with its increase of tissue oxygen partial pressure, tissue perfusion and tissue temperature in a broad variety of indications like decreasing pain and inflammation and improving wound healing - are clearly lower than the investigated disproportionally high irradiance, particularly if the difference between living skin and cell culture is taken into account. The infrared-A irradiance by the sun at the surface of the earth on sea-level in moderate climatic zones - and even in the tropics - is once more considerably lower, so that related to infrared-A irradiance and dose no indications for a necessary or sensible protection against infrared-A or wIRA - in contrast to the undisputedly sensible and necessary protection against an excessive UV irradiation - arise from the now published paper.

Original publication:
Gebbers N, Hirt-Burri N, Scaletta C, Hoffmann G, Applegate LA. Water-filtered infrared-A radiation (wIRA) is not implicated in cellular degeneration of human skin. GMS Ger Med Sci. 2007;5:Doc08.

Online available from: (PDF, approximately 6 MB) and (shtml).

Contact address:
Dr. Lee Ann Laurent-Applegate, PD & MER
Orthopedic Cell Therapy Unit
University Hospital
CH-1011 Lausanne, Switzerland
Tel: +41 21 314 3510

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