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DOI 10.1515/plm-2012-0034 Photon Lasers Med 2012; 1(4): 255–266
Review
Fatma Vatansever and Michael R. Hamblin *
Far infrared radiation (FIR): Its biological effects
and medical applications
Ferne Infrarotstrahlung: Biologische Effekte und medizinische Anwendungen
Abstract
Far infrared (FIR) radiation ( λ = 3 – 100 μ m) is a subdivision
of the electromagnetic spectrum that has been investi-
gated for biological effects. The goal of this review is to
cover the use of a further sub-division (3 – 12 μ m) of this
waveband, that has been observed in both in vitro and
in vivo studies, to stimulate cells and tissue, and is consid-
ered a promising treatment modality for certain medical
conditions. Technological advances have provided new
techniques for delivering FIR radiation to the human body.
Specialty lamps and saunas, delivering pure FIR radiation
(eliminating completely the near and mid infrared bands),
have became safe, effective, and widely used sources to
generate therapeutic effects. Fibers impregnated with FIR
emitting ceramic nanoparticles and woven into fabrics,
are being used as garments and wraps to generate FIR
radiation, and attain health benefits from its effects.
Keywords: far infrared radiation; radiant heat; black body
radiation; biogenetic rays; FIR emitting ceramics and
fibers; infrared sauna.
Zusammenfassung
Ferne Infrarotstrahlung (far infrared, FIR) ( λ = 3 – 100 μ m)
ist ein Unterbereich des elektromagnetischen Spektrums,
der hinsichtlich seiner biologischen Effekte von wissen-
schaftlichem Interesse ist. Das vorliegende Review kon-
zentriert sich auf den Spektralbereich von 3 – 12 μ m, der
sowohl in In-vitro - als auch in In-vivo -Studien mit Blick auf
die Stimulation von Zellen und Gewebe untersucht wurde
und der eine vielversprechende Behandlungsmodalit ä t
f ü r verschiedene medizinische Konditionen darstellt.
Dank des technischen Fortschrittes konnten verschie-
dene neue Techniken zur Applikation von FIR-Strahlung
am menschlichen K ö rper entwickelt werden. Spezielle
Lampen und Saunas, die reine FIR-Strahlung (ohne
Anteile von Nahinfrarot- und Mittelinfrarotstrahlung)
liefern, sind immer sicherer und effektiver geworden und
werden verbreitet f ü r therapeutische Zwecke genutzt.
Fasern, die mit FIR-emittierenden Keramik-Nanopartikeln
impr ä gniert und zu Stoffen weiterverarbeitet werden,
finden Verwendung als Kleidung oder Verbandsstoffe, die
aufgrund der generierten FIR-Strahlung gesundheitliche
Vorteile bewirken k ö nnen.
Schl ü sselw ö rter: Ferne Infrarotstrahlung (FIR); Strah-
lungsw ä rme; Schwarzk ö rperstrahlung; biogenetische
Strahlen; FIR-emittierende Keramiken und Fasern;
Infrarotsauna.
*Corresponding author: Michael R. Hamblin, Wellman Center for
Photomedicine, Massachusetts General Hospital, Boston, MA, USA,
e-mail: hamblin@helix.mgh.harvard.edu
Michael R. Hamblin: Department of Dermatology , Harvard Medical
School, Boston, MA, USA; and Harvard-MIT Division of Health
Sciences and Technology, Cambridge, MA , USA
Fatma Vatansever: Wellman Center for Photomedicine ,
Massachusetts General Hospital, Boston, MA, USA; and Department
of Dermatology, Harvard Medical School, Boston, MA , USA
1 Introduction
All living organisms are subjected to the natural electro-
magnetic radiation reaching the earth from the sun. Living
organisms experience the beneficial as well as adverse
effects of it at all levels, starting from sub-cellular orga-
nelles and ending with the whole body. Thermal radiation
(or infrared) is a band of energy in the complete electromag-
netic spectrum and it has been used effectively for millen-
nia to treat/ease certain maladies and discomforts. Heated
saunas are only one of the avenues (and perhaps the oldest)
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256F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications
to deliver the radiation in a controlled environment and
within a convenient treatment time. With the development
of better technology to deliver pure far infrared radiation
(FIR), the benefits from its effects have widened. Nowadays,
specialty FIR emitting heat lamps and garments made up of
filaments (fibers) impregnated with FIR emitting nanopar-
ticles are becoming used to deliver these thermal radiation
effects. In this paper we explore the use of FIR as a promis-
ing treatment modality for certain medical conditions. We
cover both traditional applications and novel applications,
and survey the latest technological advancements and
most recent scientific studies in the field.
1.1 What is FIR radiation ?
With respect to the complete electromagnetic radiation
spectrum, the infrared radiation (IR) band covers the
wavelength range of 750 nm – 100 μ m, frequency range of
400 THz–3 THz, and photon energy range of 12.4 meV –
1.7 eV. It lies between the long wavelength red edge of
the visible and the short edge of the terahertz (starting at
3 THz) spectral bands (Figure 1 ).
The classification of the International Commission on
Illumination (CIE) has three sub-divisions for the IR radia-
tion as given in Table 1
. An alternative classification pro-
vided in ISO 20473 standard for the sub-division of the IR
ranges is given in Table 2
.
In the IR radiation bands, only FIR transfers energy
purely in the form of heat which can be perceived by the
thermoreceptors in human skin as radiant heat [1] . Not
only is FIR absorbed by the human body but it is also
emitted by the body in the form of black body radiation
(3 – 50 μ m with an output peak at 9.4 μ m).
The term “ black body ” was first used by Gustav
Kirchoff in 1860. In essence, all matter absorbs electromag-
netic radiation to some degree and an object that absorbs
all radiation falling on it (at all wavelengths and frequen-
cies) is called a black body, i.e., a perfect absorber. When
a black body is at a uniform temperature state, it emits
back this absorbed energy, and it is termed as “ black body
radiation ” . This is a type of radiation and has continu-
ous frequency/intensity which depends only on the black
body ’ s temperature, and the type of spectrum it generates
is called the Planck spectrum. In this type of spectrum,
spectral peaks at characteristic frequencies are shifted to
higher values (shorter wavelengths) with increasing tem-
perature values. For instance, at room temperature most
of the emission of the black body is in the infrared region
of the electromagnetic spectrum. At a typical environmen-
tal background temperature, which is around 300 K, the
peak emission is at about 9.7 μ m (and the curve covers
the FIR region as well); at around 1800 K (temperature of
molten steel), the peak is shifted to 1.6 μ m; at around 6000
K (surface temperature of the sun), the peak is shifting
even further, 0.48 μ m, which now is in the visible (blue)
region of the spectrum. Peak shifts of some representative
black body temperatures and the range of electromag-
netic radiation they fall into are given in Figure 2 A, B. This
type of shift in the emission peaks of the black bodies (to
shorter wavelengths at higher temperatures) is governed
by Wien ’ s displacement law.
1.2 Biological effects of FIR
FIR application in medicine requires understanding
and knowledge of the interactions of electromagnetic
Figure 1 The spectrum of electromagnetic radiation and some
biological changes it may induce.
Name/abbreviation Wavelength Photon
energy (THz)
Near infrared/IR-A . – . m ( – nm) –
Mid infrared/IR-B . – . m ( – nm) –
Far infrared/IR-C . – m ( nm – . mm) –
Table 1 CIE classification of IR radiation.
Name/abbreviation Wavelength ( μ m)
Near IR, NIR . –
Mid IR, MIR . –
Far IR, FIR –
Table 2 ISO 20473 standard for sub-division of the IR.
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F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications 257
radiation at FIR range with biological structures (includ-
ing cells, cell membranes, cell fluids – especially water,
DNA/proteins) and functioning of the living systems in
general. At the cellular level, the underlying biophysical
mechanisms of the interaction of electromagnetic radia-
tion with living cells can be framed in terms of altered cell
membrane potentials and altered mitochondrial metabo-
lism [2] . FIR energy (photons with quantum energy levels
of 12.4 meV – 1.7 eV) is absorbed by vibrational levels of
bonds in molecules. There are six vibrational modes
covering symmetric and antisymmetric stretching, scissor-
ing, rocking, wagging and twisting. Considering the high
concentration of water in biological systems, association
of water molecules with ions (solvation effect), the dielec-
tric properties of the water and the large dipole moment
that this effect generates, this will be a dominant factor in
biological solutions. It is known that at lower frequencies
water molecules are able to rotate freely in an oscillating
electric field with little or almost no energy loss. However,
if the frequency of the electric field reaches 10
8 Hz levels,
the rotational mode becomes hindered (due to “ dielectric
friction ” effect) and the absorbed energy starts dissipating
by collision or nearest neighbor interactions in the media
[2] . The dielectric relaxation of water at 310 K is around 25
GHz where the rotational response of the dipoles to the
electromagnetic field is spread over a broad frequency
range.
In living systems, in addition to the water molecules
association with the electromagnetic field and effects
of that, one has to consider the “ meso-structure ” effect
where proteins and charged groups (located at specific
sites on the proteins) are crucial for the overall biological
activity. These specifically located charged groups associ-
ate with the water molecules and by doing this influence
the dielectric behavior of the whole molecular-assembly,
which in turn effects its biologic functioning. Thus, the
dielectric properties of tissues (even at cellular level)
depend on and vary with the water content. In addition,
the relaxation of these molecular “ meso-structures ” can
show variations with frequency. For these reasons, water
content is a critical factor in the interaction between FIR
and living organisms.
In this regard, the dynamics of water-clusters has
attracted considerable interest since there is a notice-
able difference with respect to the dynamics of bulk-
liquid-water, and this may have significant implications
in biological environments. Local changes in the mole-
cular environment (caused by solvation or confinement)
are shown to affect substantially the translational and
vibrational modes in FIR frequency range. It is found that
water cluster size and temperature affect the FIR absorp-
tion spectrum significantly [3] .
2 Medical applications of FIR
For FIR used as a therapeutic modality the alternative
terms “ biogenetic radiation ” and “ biogenetic rays ”
have been coined and widely used in the popular lit-
erature. FIR wavelength is too long to be perceived by
14,000
A
B
12,000
10,000
8000
6000
Spectral radiant emittance (W/(m2 μm))
Spectral radiance, W/(m2 μm sr)
4000
2000
0
500
1000
1500
2000
2500
3500
4000
3000
0
102
101
Water (0°C)
Water (100°C)
Radiant heater (400°C)
Tungsten
Tungsten
UV
VIS
IR-A
IR-B
IR-C
Sun
Molten steel
Fireproof stone
Human
Fireproof stone
Peak wavelength at maximum intensity (μm)
100
10-1
102103104
Temperature (K)
105
0246
1000 K
900 K
800 K
700 K
600 K
500 K
400 K
300 K
Wavelength (μm)
810
Figure 2 (A) Planck ’ s law. Dependence of spectral radiant
emittance ( ω λ ) for perfect black bodies as a function of wavelength
( λ ). (B) Wien ’ s displacement law. The wavelength of maximal radiant
exitance ( λ max ) as a function of the absolute temperature (T) for a
perfect black body (dashed line) and different bodies.
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258F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications
the eyes, however, the body experiences its energy as a
gentle radiant heat which can penetrate up to 1.5 inches
(almost 4 cm) beneath the skin. FIR energy is sufficient
to exert rotational and vibrational modes of motion in
bonds forming the molecules (including the water mol-
ecules) as well as resonate with cellular frequencies.
Resulting epidermal temperature is higher when the
skin is irradiated with FIR than if similar thermal loads
from shorter wavelengths are used. The prolonged ery-
thermal response due to FIR exposure has been pro-
posed to be due to increased epidermal temperatures
associated with it, but levels of FIR that do not produce
any detectable skin heating can also have biological
effects.
2.1 Biomedical laboratory studies using
FIR sources
2.1.1 FIR heat lamps
There have been many attempts to use FIR as a therapeu-
tic intervention where devices known as “ infrared heat
lamps ” that emit more or less FIR are been used. Unfortu-
nately, “ pure ” FIR emitting lamps are expensive, and thus,
in some instances lamps that have “ mixed ” emission, i.e.,
emit in shorter (mid infrared, MIR; near infrared, NIR
and even visible light) wavelength ranges are been used.
A common type of specialized infrared heat lamp emits
2 – 25 μ m radiation. IR saunas are often used and the most
effective types have ceramic FIR emitting panels that
remain cool to the touch. However, most IR saunas on the
market do not use the expensive FIR panels, which can be
touched since they remain always cold.
There have been a few laboratory studies that have
reported the biological effects of FIR. A recent impor-
tant paper describes the in vitro use of an FIR generator
(WS TY-301R
®
; M/s WS Far Infrared Medical Technol-
ogy Co., Ltd., Taipei, Taiwan; see Figure 3 ) as a radia-
tion source to irradiate human umbilical vein endothe-
lial cells (HUVECs) [4] . In the study, FIR exposure (a low
non-thermal irradiance) of 0.13 mW/cm
2 for 30 min inhib-
ited proliferation and the vascular endothelial growth
factor (VEGF)-induced phosphorylation of extracellular
signal-regulated kinases in HUVECs. Furthermore, FIR
exposure induced the phosphorylation of endothelial
nitric oxide synthase (eNOS) and nitric oxide (NO) gen-
eration in VEGF-treated HUVECs. Both VEGF-induced
NO and reactive oxygen species (ROS) generation was
involved in the inhibitory effect of FIR. Nitrotyrosine for-
mation increased significantly in HUVECs treated with
Figure 3 Medical FIR sources. (A) WS TY-301R ®
and (B, C) WS
TY-101N
®
FIR lamps (both by WS Far Infrared Medical Technology Co.,
Ltd., Taipei, Taiwan).
VEGF and FIR together. Inhibition of phospho inositide
3-kinase (PI3K) by wortmannin abolished both the FIR-
induced phosphorylation of eNOS and serine/threonine-
specific protein kinase in HUVECs. In addition to that,
FIR exposure upregulated the expression of PI3K p85 at
the transcriptional level. It was observed that FIR expo-
sure induced the nuclear translocation of promyelocytic
leukemia zinc finger protein in the cells. These data
provide information on how FIR exposure could affect
microcirculation, independent from thermal effects. The
same group had previously shown that non-thermal FIR
therapy increased skin blood flow in rats [5] . Toyokawa
et al. [6] used home-made ceramic FIR emitters to stimu-
late full thickness excisional skin wound healing in rats.
After constant exposure to FIR, wound healing was signifi-
cantly quickened and transforming growth factor (TGF)-
beta1 expressing myofibroblasts and collagen content
were increased.
Along the same lines, Akasaki et al. [7] studied in vivo
the effects of repeated FIR irradiation on angiogenesis in
a mouse model of hindlimb ischemia. Following reports
that FIR therapy upregulated the expression of arterial
eNOS in hamsters (and it is known that NO constitutively
produced by eNOS plays an important role in angiogen-
esis) they took a step further to investigate whether the
FIR therapy increases angiogenesis in mice with the
hindlimb ischemia. In their study, unilateral hindlimb
ischemia was induced in apolipoprotein E-deficient
mice and the group to receive the FIR irradiation was
placed in a FIR dry sauna at 41 ° C for 15 min and then
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F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications 259
at 34 ° C for 20 min once daily, with total duration of the
experiment of 5 weeks. Laser-Doppler perfusion imaging
demonstrated that at the ischemic limb, blood perfu-
sion ratio in the irradiated group increased significantly
in comparison with the control group (0.79 ± 0.04 vs.
0.54 ± 0.08, p < 0.001). Also, in the treated group, signifi-
cantly greater capillary density was observed (757 ± 123
per mm
2 vs. 416 ± 20 per mm
2 , p < 0.01). Western blotting
showed that thermal therapy has increased markedly the
hindlimb eNOS expression. Furthermore, to study pos-
sible involvement of eNOS in thermally induced angio-
genesis, the same FIR therapy was given to mice with
hindlimb ischemia with or without N(G)-nitro-L-arginine
methyl ester (L-NAME) administration for the dura-
tion of 5 weeks. It was observed that L-NAME treatment
eliminated angiogenesis induced using the FIR thermal
therapy and that the therapy did not increase angiogen-
esis in eNOS-deficient mice. The study led to the conclu-
sion that angiogenesis can be induced via eNOS using
FIR thermal therapy in mice with hindlimb ischemia.
Ishibashi et al. [8] did an in vitro study with
five human cancer cell lines (A431, vulva; HSC3,
tongue; Sa3, gingival; A549, lung; and MCF7, breast)
to assess the effects of FIR irradiation. For that
purpose, they used a tissue culture incubator with
an imbedded FIR lamp that could continuously irra-
diate cells with FIR (lamp operating wavelength
range being 4 – 20 μ m with an emission peak height at
7 – 12 μ m). The overall observation was that the FIR effect
varied in these five cancer cell line types, as can be
expected. The study results showed that basal expres-
sion level of heat shock protein (HSP) 70A mRNA was
higher in A431 and MCF7 cell lines in comparison with
the FIR-sensitive HSC3, Sa3, and A549 cell lines. The
study showed that the over expression of HSP70 inhib-
ited FIR-induced growth arrest in HSC3 cells, and that
HSP70 siRNA inhibited the proliferation of A431 cells
after FIR treatment. A summary of the results of this
study indicated that the proliferation-suppressing effect
of FIR, in some cancer cell lines, is controlled by the
basal expression level of the HSP70A. These findings
suggest that FIR irradiation may be used as an effective
medical treatment avenue for some cancer cells which
have low levels of HSP70.
2.1.2 FIR emitting ceramics and fabrics
FIR emitting ceramics have been known for some time
[9, 10] . All ceramics have the property of emitting IR
radiation depending on their temperature. In the age
of gas lighting, ceramic mantles were heated by gas
flames to emit both IR and visible radiation depending
on the temperature attained. The exact chemical compo-
sition of the ceramic material governs the relationship
between the temperature and the amount of IR radia-
tion. The radiated energy follows the Stefan-Boltzmann
law which says that the total energy radiated per unit
of surface area per unit of time is directly proportional to
the fourth power of the black body ’ s absolute tempera-
ture. The wavelength range also depends strictly on the
temperature according to Wien ’ s displacement law [11] .
The boron-silicate mineral, tourmaline (known as
a gemstone in its crystalline form) when milled into fine
powders also emits FIR [12] and the characteristics of the
FIR emission depend on the particle size. Preparations
containing tourmaline powder have been applied to the
skin with the aim of affecting the blood flow [13] . In a
similar manner discs of FIR emitting ceramics have been
attached to the skin with the intent of producing a benefi-
cial effect (see later).
Small particles (nanoparticles and microparticles)
of FIR-emitting ceramic material have been incorporated
into fibers that are then woven into fabrics. These fabrics
can be manufactured into various garments that can be
worn on different parts of the body.
When FIR emitting ceramics or fabrics are employed
as therapeutic devices, it is pertinent to analyze the ther-
modynamics of the process. The first law of thermodynam-
ics states that energy can neither be created nor destroyed.
Heat (molecular vibrational energy) is transferred from
one body to another in three forms: radiation, convec-
tion and conduction. Thus, it is clear that the principle
source of energy needed to power the FIR emission from
the garments comes from the human body, since it is at
a significantly higher temperature than the surrounding
air. So energy from the human body is transferred to these
ceramic particles, which are acting as “ perfect absorb-
ers ” , maintain their temperature at sufficiently high levels
and then emit FIR back to the body. It is plausible that FIR
emitted from the skin is absorbed by the ceramic parti-
cles, which then re-emit the same FIR back to the skin.
Although this may appear to be an energy neutral process
and to cancel itself out, this is not in fact the case because
the FIR emitting material will prevent the loss of FIR that
would otherwise have escaped through normal clothing.
However the same effect could have been achieved with
a FIR reflective foil suit or suchlike. Other sources of heat
that can transfer energy from the body to the ceramic par-
ticles with a net gain of FIR are either convection, conduc-
tion, or both. The balance between conduction and con-
vection will depend on how close the contact is between
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260F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications
the garment and the skin. If the garment is skin tight, then
conduction may be important, while if it is loose fitting
then convection (heating up a layer of air between the skin
and the garment) may be important.
Ting-Kai Leung and colleagues have studied the
effect of FIR-emitting ceramic powders in a range of bio-
logical studies [14 – 19] . In one set of studies, they cul-
tured murine myoblast cells (C2C12) with bags of ceramic
powder under the culture plates and found that FIR
irradiation improved cell viability and prevented lactate
dehydrogenase release under hydrogen peroxide (H
2 O 2 )-
mediated oxidative stress, and also elevated the intracel-
lular levels of NO and calmodulin [14] . In the study, they
used electro-stimulation of amphibian skeletal muscle
and found that FIR emitting ceramics delayed the onset of
fatigue, induced by muscle contractions [14] . In another
set of studies, they showed that ceramic-emitted FIR
(cFIR) could increase the generation of intracellular NO
in breast cancer cells [15] and inhibit growth of murine
melanoma cells [16] . Similarly, they found that cFIR
increased calmodulin and NO production in RAW 264.7
macrophages [17] . cFIR also has been shown to increase
the viability of murine macrophages with different con-
centrations of H
2 O 2 [15] . In this study [15] it was shown
that cFIR significantly inhibited intracellular peroxide
levels and lipopolysaccharide (LPS)-induced peroxide
production by macrophages. In the same study, it was
also demonstrated that cFIR blocked ROS-mediated cyto-
toxicity (shown by measurements of cytochrome c and
the ratio of NADP + /NADPH) [15] .
The same research group went on to study a rabbit
model of rheumatoid arthritis in which rabbits received
intra-articular injections of LPS to induce inflam-
mation that mimics the rheumatoid arthritis [18] .
Fluorodeoxyglucose(
18 F) coupled with positron emission
tomography (FDG-PET) scans were used to monitor the
inflammation in 16 h and 7 days after the LPS injection.
Rabbits to be treated with cFIR were placed in a cage sur-
rounded by paper sheets impregnated with a thin layer
of the ceramic powder, while the control group was sur-
rounded by the same sheet without the material. Compari-
son of the final and initial uptakes of FDG isotopes in the
LPS-injected left knee-joints of the rabbits indicated larger
decreases in the cFIR exposed group than in the control
group indicating that FIR reduced inflammation.
In their most recent study the Leung group studied
the repair effect of cFIR in human breast epithelial cells
(MCF-10A) after H
2 O 2 and after ionizing radiation from an
X-ray source [19] . Their results show that in both, H
2 O 2 toxi-
city and radiation exposure models, the cFIR treated cells
demonstrated significantly higher cell survival rates than
the control groups. In view of the experimental results
and taking into account the relationship between indirect
ionizing radiation and the oxidative stress-induced cell
damage, and accumulation of free radicals, they proposed
that the ionizing radiation protective ability of cFIR occurs
predominantly through an antioxidant mechanism. They
are suggesting that cFIR provides cells with a defensive
mechanism during the irradiation process and promotes
cell repair during post exposure period through hydrogen
peroxide scavenging and COX-2 inhibiting activities.
2.2 Means that are used to deliver the
FIR radiation
We analyzed the peer-reviewed applications of therapeu-
tic FIR delivery systems and realized that there are three
main techniques for FIR radiation delivery: i) FIR saunas,
ii) FIR ray devices and iii) FIR emitting ceramics and
fabrics.
2.2.1 FIR saunas
In these cabins, the heating elements are typically heated
to about 300 – 400 ° C and the emission is in the FIR range,
that is, the heat exchange between the body and the envi-
ronment is almost purely radiative (radiant heating) with
cabin air temperature being at around 40 ° C or less (Figure
4 ). Heating of the skin with FIR warming cabins is faster
(in comparison with the conventional saunas) but higher
irradiance of the skin must be applied in order to produce
noticeable sweating. These cabins are frequently used in
Japan where the practice is called “ Waon therapy ” [20,
21] . Waon therapy has been used extensively in Japan
[22] and Korea [23] for cardiovascular conditions and
diseases, particularly chronic heart failure [24, 25] and
peripheral arterial disease [26, 27] . FIR sauna therapy
has been used to improve cardiac and vascular func-
tion and reduce oxidative stress in patients with chronic
heart failure [28] . Beever [29] asked whether FIR saunas
could have a beneficial effect on quality of life in those
patients with type II diabetes. The study consisted of
20 min, three times weekly infrared sauna sessions, over
a period of 3 months. Physical health, general health,
social functioning indices, and visual analogue scales
(VAS) measurements for stress and fatigue all improved
in the treatment group. A study of patients with rheuma-
toid arthritis and ankylosing spondylitis showed a reduc-
tion in pain, stiffness, and fatigue during infrared sauna
therapy [30] .
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F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications 261
2.2.2 FIR ray devices
Common devices are WS TY-101N
®
and WS TY-301R
®
(made by WS Far Infrared Medical Technology Co., Ltd.,
Taipei, Taiwan; see Figure 3). A report from Hu and Li
[31] describes the treatment of allergic rhinitis. A WS
TY-101N
®
FIR emitter was placed 30 cm from the patient ’ s
nasal region. The treatment was performed for 40 min
every morning for 7 days. Every day, patients recorded
their symptoms in a diary before and during treatment.
Each symptom of rhinitis was rated on a 4-point scale
(0 – 3) according to severity. During the period of FIR
therapy, the symptoms of eye itching, nasal itching,
nasal stuffiness, rhinorrhea, and sneezing were all sig-
nificantly improved. Smell impairment was improved
after the last treatment. Lin et al. [32] used a WS TY-101N
®
FIR emitter to treat vascular access malfunction with
an inadequate access flow (Qa) in hemodialysis (HD)
patients. This randomized trial demonstrated that
FIR therapy could improve access flow and potency of
the native arteriovenous fistula (AVF) in a total of 145
HD patients (73 in the control group and 72 in the FIR-
treated group). FIR was used for 40 min, and hemody-
namic parameters were measured by the HD02 monitor
(M/s Transonic System Inc.), during the hemodialysis. In
comparison with control subjects, patients who received
FIR therapy for 1 year had a lower incidence (12.5 vs.
30.1 % ; p < 0.01) and relative incidence (one episode per
67.7 vs. one episode per 26.7 patient-months; p = 0.03) of
AVF malfunction. Hausswirth et al. [33] showed that FIR
therapy reduced symptoms of exercise-induced muscle
damage in athletes after a simulated trail running race.
2.2.3 FIR emitting ceramics and fabrics
Discs and garments manufactured of FIR emitting ceramic
material have been applied to the human body (Figure 5 ).
For instance, a blanket containing discs has been reported
to improve quality of sleep [34] and single discs were
applied to the breasts of women who encountered diffi-
culty in producing sufficient breast milk during lactation
[35] . Gloves have been made out of FIR emitting fabrics and
there have been reports that these gloves can be used to
treat arthritis of the hands and Raynaud ’ s syndrome [36] .
Belts made out of these fabrics have been used for
weight reduction. In one study, Conrado and Munin [37]
investigated whether the use of a garment made with
synthetic fibers embedded with powdered ceramic led
to a reduction in body measurements. The study popula-
tion comprised 42 women divided into two groups: active
and placebo. The volunteers used clothing either impreg-
nated or not impregnated with ceramic powder for at least
8 h/day for 30 days. The experimental data showed a
reduction in body measurements, which may be a conse-
quence of an increment in microcirculation and peripheral
blood flow, and these changes might promote improved
general health.
A belt containing FIR-emitting sericite mineral (a fine
grained mica) was used to study the relief of menstrual
FIR sauna
AB
Hot
stove
C
Conventional sauna
Figure 4 FIR sauna. (A, B) Comparison of FIR sauna with conventional heated sauna. (C) Cabin incorporating FIR emitting “ cold ” unit(s)
(Anhui Hi-Tech Electronic Commerce Co., Ltd., Hefei, China).
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262F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications
pain [38] . In this study, 104 patients with primary dys-
menorrhea were randomized to wear a sericite or
placebo belt during sleep for three menstrual cycles, and
then followed up for two additional menstrual cycles
with no belt. Hot packs were used to heat the ceramics
and ensure slight pain relief in both groups. Although
the severity of dysmenorrhea decreased during the treat-
ment period in both groups, it was found that during
the follow-up period, the decreased VAS (pain) score
was maintained in the experimental group, whereas the
VAS score gradually returned to baseline in the control
group, which resulted in significant difference between
the groups (p = 0.0017).
In their recent clinical study, Liau et al. [39] looked
into the benefits of using an FIR emitting belt for manag-
ing the discomfort of primary dysmenorrhea in female
patients. Taking into account several parameters, such
as body temperature, abdominal blood flow, pain assess-
ment, and heart rate variability, they showed that FIR
belts used increased the local surface body temperature
as well as the abdominal blood flow; in addition to reduc-
ing the pain and the discomfort from it. In this particular
study, a THERMEDIC FIR belt (LinkWin Technology Co.,
Ltd., Taiwan) with the capability to generate 11.34 mW/
cm
2 at 50 ° C was used.
Rao et al. [40] used garments made out of bioceramic-
coated neoprene in conjunction with a “ topical cream ” to
treat cellulite of the legs. Each subject was randomized
to receive occlusion by the garment on either the right or
left leg, with the contralateral side serving as a control
with no occlusion. Of the 17 subjects who completed the
study, 76 % noticed an overall improvement in their cellu-
lite, with 54 % reporting greater improvement in the thigh
that received garment occlusion. Further, the evaluators
found the occluded thighs to show greater improvement
than the non-occluded thighs in 65 % of subjects. Biocer-
amic-coated neoprene garment occlusion potentiated the
effect of the topical agent in cellulite reduction. A follow
up two-center, double-blinded, randomized trial found
similar results [41] .
Celliant
®
(Hologenix, Santa Monica, CA, USA) is a
polyethylene terephthalate (PET) fiber that incorporates
FIR emitting ceramic nanoparticles. York and Gordon
[42] studied socks manufactured from Celliant
®
fiber
material in patients with chronic foot pain resulting from
diabetic neuropathy or other disorders. A double-blind,
A
G
H
I
J
K
C
B
D
E
F
Figure 5 FIR emitting garments and fabrics manufactured from fibers impregnated with ceramic nanoparticles (Celliant
®
, Hologenix,
Santa Monica, CA, USA). (A) fibers, (B) yarns, (C) fabrics, (D) knee bandage brace, (E) socks, (F) gloves, (G) elbow bandage brace,
(H) multi-purpose bandage, (I) performance apparel, (J) mattress, and (K) puppy blanket.
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F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications 263
randomized trial with 55 subjects (38 men, 17 women,
average age 59.7 ± 11.9 years) enrolled 26 patients with
diabetic neuropathy and 29 with other pain etiologies.
Subjects twice completed the VAS, brief pain inventory
(BPI), McGill pain questionnaire (MPQ), and a multipur-
pose, short form health survey with 36 questions (SF-36)
a week apart [W(1 + 2)] before receiving either control or
Celliant
®
socks. The same questionnaires were answered
again 1 and 2 weeks later [W(3 + 4)]. The questionnaires
provided nine scores for analyzing pain reduction: one
VAS score, two BPI scores, five MPQ scores, and the
bodily pain score on the SF-36. Mean W(1 + 2) and W(3 + 4)
scores were compared to measure pain reduction. More
pain reduction was reported by Celliant
®
subjects for
eight of the nine pain questions employed, with a signifi-
cant (p = 0.043) difference between controls and Celliant
®
for McGill question III. In neuropathic subjects, Celliant
®
caused greater pain reduction in six of the nine questions,
but not significantly. In non-neuropathic subjects eight of
nine questions showed better pain reduction with the
Celliant
®
socks.
3 Hypothesis for molecular
and cellular mechanisms of
FIR effects
Despite all these different uses of FIR in medical applica-
tions, the exact mechanisms of the hyperthermic effects
and biological activities of FIR irradiation are still poorly
understood. It is clear that two kinds of FIR therapy may
exist. The first type (FIR saunas and some FIR generators
powered by electricity) uses irradiances or power densi-
ties (tens of mW/cm
2 ) that are sufficient to heat up the
tissue, while others such as ceramic discs, powders, and
fabrics (that use no external power but rely on energy
from the body) have such low irradiances that they do
not heat the tissue (0.1 – 5 mW/cm
2 ). The question arises
to what extent are the fundamental mechanisms of these
two forms of FIR therapy the same, and to what extent are
they different ? Furthermore, the question may be posed
as to what degree of similarity that FIR therapy has with
the reasonably well-established therapy called low level
laser (light) therapy (LLLT) also known as photobiomo-
dulation (PBM). Pertinent to this question is the fact that
many devices used to deliver therapeutic visible or NIR
light were approved by the US Food and Drug Adminis-
tration as being equivalent to an “ infrared heat lamp ” .
The cellular and molecular mechanisms of LLLT/PBM
are to some extent understood and involve absorption of
red or NIR light by mitochondrial chromophores such as
cytochrome c oxidase (CCO, unit IV of the mitochondrial
respiratory chain) [43] . This photon absorption activates
the enzyme possibly by photo-dissociating the inhibitory
molecule, NO, from the copper B (CuB) site [44] . This loss
of NO allows electron transport, oxygen consumption,
and adenosine triphosphate (ATP) to rapidly increase
and results in a marked rise in mitochondrial membrane
potential (MMP) that gives rise to a brief burst of ROS [45] .
Signaling pathways are activated by ATP, NO, and ROS
and these lead to activation of transcription factors (such
as NF- κ B) [46] that lead to the long-term effects on tissue
(healing, anti-inflammatory and pain relief [47] ) seen after
relatively transient periods of illumination.
Since the principle chromophore at FIR wavelengths
is not CCO but rather water, we must ask ourselves how
can the biological effects of red and NIR absorption be
so similar to those seen with FIR ? Perhaps some clue
can be obtained by considering the difference between
the two types of FIR therapy (heating and non-heating).
While heating FIR therapy is reported to increase blood
flow, this result may be the simple response of increased
thermoregulation that is known to occur when tissue
is warmed. However, it is possible that the increase in
blood flow, seen in non-heating FIR therapy, may be
similar in nature to that seen in LLLT, in other words, a
vasodilation due to NO release from stores in CCO [48]
as well as from NO bound to hemoglobin and myoglo-
bin [49] . How are we to explain cellular responses from
low fluences of FIR that are insufficient to produce
bulk heating of water in the tissue ? Perhaps the answer
lies in the concept of nanostructured water layers [50] .
These are thin (nano meters) layers of water that build
up on hydrophobic surfaces such as cellular mem-
branes, and they can be considered as “ concentrated
water ” [51] . If this description is correct, it is reasonable
to assume that relatively small amounts of vibrational
energy delivered by non-heating FIR could perturb the
structure of the membrane underlying the nanoscopic
water layer without bulk heating. Small perturbations
in membrane structure could have big effects at the
cell level if the membrane contains an ion channel. Ion
channels (many kinds for both cations and anions [52] )
are present in all cell membranes, but are particularly
common in mitochondrial membranes (both inner and
outer [53] ). If mitochondrial ion channels (particularly
calcium channels [54] ) could be opened by non-heating
FIR, thus increasing mitochondrial respiration, it would
explain how the overall therapeutic outcomes of LLLT
and non-heating FIR therapy are so similar.
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264F. Vatansever and M.R. Hamblin: FIR: Its biological effects and medical applications
It cannot be excluded that FIR could itself have effects
on CCO activity. A recent study has elucidated the exist-
ence of weakly H-bonded water molecules in bovine
CCO that might change during catalysis [55] . Fitting with
Gaussian components indicated the involvement of up
to eight waters in the photolysis transition. The fact that
Fourier transform infrared (FTIR) spectroscopy is exten-
sively employed to study the structure, function, and
dynamics of CCO [56, 57] suggests that it is possible that
the same wavelengths (FIR uses comparable wavelengths
to FTIR) could produce changes in conformation affecting
enzyme activity or binding of NO to the CuB site.
It must be emphasized that the above remains a hypo-
thetical explanation at present, but is clearly a testable
hypothesis. One could ask whether exposure of cells to non-
heating FIR can affect mitochondria by for instance increas-
ing ATP, increasing oxygen consumption, producing NO
and ROS, affecting MMP and calcium levels. One could also
ask whether cells that are rich in mitochondria respond well
to non-heating FIR, in the same way as they do to LLLT.
4 Conclusion
If it can be proved that non-heating FIR has real and sig-
nificant biological effects, then the possible future appli-
cations are wide ranging. Not only could bandages and
dressings made out of NIR emitting fabrics be applied
for many medical conditions and injuries that require
healing, but there is a large potential market in lifestyle
enhancing applications. Garments may be manufactured
for performance enhancing apparel in both leisure activi-
ties and competitive sports areas. Cold weather apparel
would perform better by incorporating FIR emitting capa-
bility and sleeping environments could be improved by
mattresses and bedding emitting FIR.
Acknowledgements: This work was supported by the US
NIH (R01AI050875 to MRH).
Received August 24, 2012; revised September 6, 2012; accepted
September 6, 2012 ; previously published online October 16, 2012
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