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Red Light Therapy; Indications, Contraindications

Red Light Therapy/ Infrared Radiation Therapy (IR) sometimes called infrared light is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye, although IR at wavelengths up to 1050 nanometers (nm)s from especially pulsed lasers can be seen by humans under certain conditions.^[rx]^[rx] IR wavelengths extend from the nominal red edge of the visible spectrum at 700 nanometers (frequency 430 THz), to 1 millimeter (300 GHz).^[rx] Most of the thermal radiation emitted by objects near room temperature is infrared. As with all EMR, IR carries radiant energy and behaves both like a wave and like its quantum particle, the photon.

Infrared (IR) radiation is electromagnetic radiation with wavelengths between 760 nm and 100,000 nm. Low-level light therapy (LLLT) or photobiomodulation (PBM) therapy generally employs light at red and near-infrared wavelengths (600–100 nm) to modulate biological activity. Many factors, conditions, and parameters influence the therapeutic effects of IR, including fluency, irradiance, treatment timing and repetition, pulsing, and wavelength. Increasing evidence suggests that IR can carry out photostimulation and photobiomodulation effects particularly benefiting neural stimulation, wound healing, and cancer treatment. Nerve cells respond particularly well to IR, which has been proposed for a range of neurostimulation and neuromodulation applications, and recent progress in neural stimulation and regeneration are discussed in this review.

Another Name

You may have heard of red light therapy (RLT) by its other names, which include:

Photobiomodulation (PBM)
Low-level light therapy (LLLT)
Soft laser therapy
Cold laser therapy
Biostimulation
Photonic stimulation
Low-power laser therapy (LPLT)

Types of Infrared Radiation Therapy

IR is divided into different bands: Near-Infrared (NIR, 0.78~3.0 μm), Mid-Infrared (MIR, 3.0~50.0 μm) and Far-Infrared (FIR, 50.0~1000.0 μm) as defined in standard ISO 20473:2007 Optics and photonics — Spectral bands [1]

Infrared light immediately follows red light on the electromagnetic spectrum. Infrared (IR) light energy is broken down into three groups:

Near Infrared – also called infrared-A (IR-A). Near IR spans wavelengths 760 to 1,400 nm. Most home therapy devices use these wavelengths.
Mid Infrared – also called infrared B (IR-B) – These wavelengths are used in many household electronic devices such as remote controls.
Far Infrared – or IR-C– also known as longwave infrared, thermal infrared (thermal-IR). This is the largest part of the IR spectrum, used in infrared saunas.

Most studies showing benefits of red/NIR light therapy used light outputs of 20-200mW/cm². This is basically a measurement of power density – how much power the light is emitting (in watts) over how big of an area. To put that in different terms, if you shine the light on your torso (let’s say, for the sake of ease of calculation, that it’s an area of 50cm x 40cm, which equals 2,000cm²). And the light you’re using is 200 watts (which is 200,000mW), then you have 200,000mW/2,000cm² = 100mW/cm²

Commonly Used Sub-Division Scheme

A commonly used sub-division scheme is:^[rx]

Division name	Abbreviation	Wavelength	Frequency	Photon energy	Temperature^[rx]	Characteristics
Near-infrared	NIR, IR-A DIN	0.75–1.4 µm	214–400 THz	886–1653 meV	3,864–2,070 K (3,591–1,797 °C)	Defined by water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO₂ glass (silica) medium. Image intensifiers are sensitive to this area of the spectrum; examples include night vision devices such as night vision goggles. Near-infrared spectroscopy is another common application.
Short-wavelength infrared	SWIR, IR-B DIN	1.4–3 µm	100–214 THz	413–886 meV	2,070–966 K (1,797–693 °C)	Water absorption increases significantly at 1450 nm. The 1530 to 1560 nm range is the dominant spectral region for long-distance telecommunications.
Mid-wavelength infrared	MWIR, IR-C DIN; MidIR.^[rx] Also called intermediate infrared (IIR)	3–8 µm	37–100 THz	155–413 meV	966–362 K (693–89 °C)	In guided missile technology the 3–5 µm portion of this band is the atmospheric window in which the homing heads of passive IR ‘heat seeking’ missiles are designed to work, homing on to the Infrared signature of the target aircraft, typically the jet engine exhaust plume. This region is also known as thermal infrared.
Long-wavelength infrared	LWIR, IR-C DIN	8–15 µm	20–37 THz	83–155 meV	362–193 K (89 – −80 °C)	The “thermal imaging” region, in which sensors can obtain a completely passive image of objects only slightly higher in temperature than room temperature – for example, the human body – based on thermal emissions only and requiring no illumination such as the sun, moon, or infrared illuminator. This region is also called the “thermal infrared”.
Far infrared	FIR	15–1000 µm	0.3–20 THz	1.2–83 meV	193–3 K (−80.15 – −270.15 °C)	(see also far-infrared laser and far infrared)

NIR and SWIR are sometimes called “reflected infrared”, whereas MWIR and LWIR is sometimes referred to as “thermal infrared”. Due to the nature of the blackbody radiation curves, typical “hot” objects, such as exhaust pipes, often appear brighter in the MW compared to the same object viewed in the LW.

A third scheme divides up the band based on the response of various detectors:^[rx]

Near-infrared – from 0.7 to 1.0 µm (from the approximate end of the response of the human eye to that of silicon).
Short-wave infrared – 1.0 to 3 µm (from the cut-off of silicon to that of the MWIR atmospheric window). InGaAs covers to about 1.8 µm; the less sensitive lead salts cover this region.
Mid-wave infrared – 3 to 5 µm (defined by the atmospheric window and covered by indium antimonide [InSb] and mercury cadmium telluride [HgCdTe] and partially by lead selenide [PbSe]).
Long-wave infrared – 8 to 12, or 7 to 14 µm (this is the atmospheric window covered by HgCdTe and microbolometers).
Very-long wave infrared (VLWIR) – (12 to about 30 µm, covered by doped silicon).

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Indications of Infrared Radiation Therapy

Additional clinical research is needed to prove that RLT is effective. At the moment, however, there’s some evidence to suggest that RLT may have the following benefits:

Promotes wound healing and tissue repair
Improves hair growth in people with androgenic alopecia
Help for the short-term treatment of carpal tunnel syndrome
Stimulates healing of slow-healing wounds, like diabetic foot ulcers
Skin Wounds
Photo prevention
Relieve pain
Stiffness
Fatigue of rheumatoid arthritis
Ankylosing spondylitis
Potentiate photodynamic therapy
Treat ophthalmic, neurological, and psychiatric disorders, and
Stimulate the proliferation of mesenchymal and cardiac stem cells
Reduces psoriasis lesions
Aids with short-term relief of pain and morning stiffness in people with rheumatoid arthritis
reduces some of the side effects of cancer treatments, including oral mucositis
Improves skin complexion and builds collagen to diminish wrinkles
Helps to mend sun damage
Prevents recurring cold sores from herpes simplex virus infections
Improves the health of joints in people with degenerative osteoarthritis of the knee
Helps diminish scars
Relieves pain and inflammation in people with pain in the Achilles’ tendons
Reduce the signs of damage, DNA damage,^[rx] and aging from UV rays^[rx]
Reduce wrinkles^[rx]
Reduce color patches, hyperpigmentation, and skin discoloration^[rx]
Enhance collagen synthesis and collagen density (research has shown it can enhance production of collagen by 31%)^[rx]^,^[rx]
Accelerate repair in the epithelial layer of skin
Combat other skin conditions like acne, keloids, vitiligo, burns, herpes virus sores, and psoriasis
Speed wound healing by enhancing skin tissue repair and growth of skin cells
Chronic neck ^pain[rx]
Knee pain^[rx]
Fibromyalgia
Low back pain
Chronic pain in the elbow, wrist, and fingers
Chronic joint disorders
Sacroiliac joint pain
Chronic tooth pain
Osteoarthritic pain
Tendinitis and myofascial pain^[rx]
Benefit cognitive performance and memory
The improved mitochondrial function of brain cells
Have a protective effect on neurons
Improve cellular repair of neurons
Increase brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF)
Decrease brain inflammation (decreased pro-inflammatory cytokines and increased anti-inflammatory cytokines)

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Various medical applications of IR radiation for different cells and tissue tissues.

Medical Applications	Author, reference	Target	The light source or material	Wavelengths	Results
Wound Healing	Toyokawa et al. [rx]	Skin wound in rat	Ceramic-coated sheet	5.6 ~ 25 μm (maximal intensity of 8 ~ 12 μm)	Promoted wound healing and expression of TGF-β1
Wound Healing	Gupta et al. [rx]	Dermal abrasions in mice	Diode laser	810 nm	Enhanced collagen accumulation and healing effects
Wound Healing	Santana-Blank et al. [rx, rx]	Soft tissues in the rat	Diode laser	904nm	Promotes wound healing and exclusion zone (EZ) growth (1H-NMR 1/T2)
Wound Healing	Santana-Blank et al. [rx] Rodríguez-Santana et al.[rx]	Soft tissues in the rat	Diode laser	904nm	Promotes wound healing, membrane effect measured by 1H-NMR tau(c)
Neural Stimulation	Wells et al. [rx]	Rat sciatic nerve	Free electron laser	2.1, 3.0, 4.0, 4.5, 5.0, and 6.1 μm	Generated a spatially selective response in small fascicles of the sciatic nerve
Neural Stimulation	Jenkins et al. [rx]	Adult rabbit heart	Diode laser	1.851μm	Induced optical pacing of the adult rabbit heart
Neural Stimulation	Izzo et al. [rx]	Gerbils auditory nerve	Holmium: YA G laser	2.12 μm	Optical radiation stimulated the cochlear response amplitudes
Neural Stimulation	Duke et al. [rx]	Rat sciatic nerve	Diode laser	1.875μm	Hybrid electro-optical stimulation generated sustained muscle contractions and reduced the laser power requirements
Neural Stimulation	Shapiro et al. [rx]	HEK-293T cells	Diode laser	1.889 μm	Altered the membrane electrical capacitance during optical stimulation transiently
Photoaging	Darvin et al. [rx]	Human skin	Radiator equipped with a water filter	600 ~1500 nm	Formed free radicals and decreased the content of β carotene antioxidants
Photoaging	Schroeder et al. [rx]	Human dermal fibroblasts	Water-filtered IR-A irradiation source	760~14 40 nm	Increased expression of MMP-1 in the dermis
Antitum or Action	Tsai et al. [rx]	HeLa cervical cancer cell	Waveguide Thermal Emitter	3.6, 4.1 or 5.0 μm	Caused a collapse of mitochondria l membrane potential and an increase in oxidative stress.
AntitumorAction	Chang et al. [rx]	Breast cancer cells and normal breast epithelial cells.	Blackbody source equipped with 3~5 μm filter	3~5 μm	Induced G ₂ /M cancer cell cycle arrest, remodeled the microtubule network and altered the actin filament formation
Antitumor Action	Tanaka et al. [rx]	A549 lung adenocarcinoma cells	NIR radiator equipped with a water filter	1.1~1.8 μm	Activated the DNA damage response pathway
AAntitumorAction	Yamashita et al. [rx]	A431 (vulva), A549 (lung), HSC3 (tongue), MCF7 (breast) and Sa3 (gingiva) cancer cells	FIR radiant-panel incubator by coating a carbon/silica/aluminum oxide/titanium oxide ceramic	4~20 μm (maximum at 7 to 12 μm)	Suppressed the proliferation of cancer cells through enhancing the expression of ATF3 gene
Antitumor Action	Santana-Blank et al.[rx]	Solid tumor Clinical trial	Diode laser	904nm	88% anticancer effect. Ten years follow up
Antitumor Action	Santana-Blank et al.[rx]	Solid tumor cytomorphology	Diode laser	904nm	Selective apoptosis, necrosis, anoikis in tumor tissues of cancer patients
Antitumor Action	Santana-Blank et al. [rx]	Solid tumor T_2wMRI-Microdensitometry	Diode laser	904nm	Evidence of interfacial water exclusion zone (EZ) as a predictor of anti-tumor response in cancer patients
Antitumor Action	Santana-Blanket al.[rx]	Solid tumor serum levels of cytokines of peripheral leucocyte subsets	Diode laser	904nm	Immuno-modulation in cancer patients of TNF-α SIL-2R and CD4+CD45 RA+ and CD25+ activated
Brain Neural Regeneration	Naeser et al. [rx]	Mild traumatic brain injury	NIR diodes	870 nm	Improved cognitive function, sleep and post-traumatic stress disorder symptoms
Brain Neural Regeneration	Lapchak et al. [rx]	Strokes in embolized rabbits	Laser source	808 nm	Increased cortical ATP content
Adipose Regeneration	Wang, Y., et al. [rx]	human adipose-derived stem cells	Diode laser	810 nm 980nm	Stimulate the proliferation and differentiation

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Contraindication of Red Light Therapy

Treatment Contraindications forIRR Light Therapy

Open wounds
Metastatic Lesions
Areas of decreased sensation
parts of the body with metal implants, like in a total knee replacement of lumbar fusion
Near or over a pacemaker
the uterus during pregnancy
Over the gonads
Malignancies and precancerous lesions
On patients with vascular abnormalities, i.e. deep vein thrombosis, emboli, severe atherosclerosis
The eye directly
Over the stellate ganglion
For hemophiliacs not covered by factor replacement
The spinal cord after laminectomy
Directly over metal implants
Over an electronic device
Tissues previously treated with deep Xray or radiation
Tuberculosis (local)
Damaged or at-risk skin, i.e. skin rash, eczema
Anesthetic areas
Excitable tissue,
With pregnant women
Around the eyes, breasts, or sexual organs
Over fractured bones
Near or over an implanted electrical stimulation device
Women who are pregnant should consult their physician before beginning IRR light therapy treatments.
Clients with epilepsy should consult their physician before beginning IRR light therapy treatments.
You must wait five days after Botox or cosmetic fillers.
Some thyroid conditions.
People with a history of skin cancer
Systemic Lupus erythematosus should also avoid this kind of treatment.
The use of photosensitizing medications (i.e. lithium, melatonin, phenothiazine antipsychotics, and certain antibiotics).
Diseases that involve the retina of the eye