TITLE:
Beneficial Applications and Deleterious Effects of Near-Infrared from Biological and Medical Perspectives
AUTHORS:
Yohei Tanaka, Lisa Gale
KEYWORDS:
Biological Effects; Near-Infrared; Non-Thermal; Water-Filter
JOURNAL NAME:
Optics and Photonics Journal,
Vol.3 No.4A,
August
9,
2013
ABSTRACT:
Over half of solar energy consists of near-infrared and
a wide range of preventative mechanisms have been evolutionarily maintained in
organisms to protect against effects of near-infrared. However, the biological
effects of near-infrared have not been investigated in detail. Despite the essential requirement of a water-filter
to imitate solar near-infrared filtered by atmospheric water, previous studies used near-infrared resources without
a water-filter or a cooling system. With these methods, near-infrared energy is
primarily absorbed in the superficial tissues, thus these approaches are unable
to sufficiently evaluate the biological effects of solar near-infrared that
reaches human tissue. We have elucidated that near-infrared (1100 - 1800 nm together with a
water-filter that excludes wavelengths 1400 - 1500 nm) non-thermally affects the
skin into the deeper tissues. The biological effects of near-infrared have both beneficial applications
and deleterious effects. Near-infrared induces collagen and elastin stimulation, which achieves skin rejuvenation
and skin tightening, and induces long-lasting vasodilation that may prevent
vasospasm and be beneficial for ischemic disorders. Near-infrared also relaxes and weakens dystonic and hypertrophic
muscles to reduce wrinkles and myalgia. Nearinfrared is
an essential tool in cancer detection and
imaging, and induces drastic non-thermal DNA damage of
mitotic cells, which may be beneficial for treating cancer. Activation of stem cells by near-infrared may be useful in regenerative medicine. However,
continuous near-infrared exposure induces photoaging and potentially
photocarcinogenesis. Humans have protective
mechanisms against near-infrared on
multiple levels, including perspiration, blisters, vasodilation,
hair, skin, adipose tissue, and cotton or wool clothing. Further protection should be considered,
as biological effects of near-infrared are significant, and standard sunscreens
and glasses cannot sufficiently block near-infrared. This paper reviews the
effects of near-infrared and introduces the new findings of near-infrared from
a biological point of view.