Dermatological Effects of Red and Near Infrared Light Exposure
Red and near-infrared light exposure has both beneficial and potentially harmful dermatological effects, with outcomes largely dependent on wavelength, intensity, and duration of exposure. The therapeutic benefits include collagen and elastin production, wound healing, and anti-aging effects when used at appropriate intensities, while potential risks include pain, hyperpigmentation, and possible carcinogenicity with improper application 1, 2, 3.
Beneficial Dermatological Effects
Collagen and Elastin Production
- Low-level red (640 nm) plus near-infrared (830 nm) light combination at 0.5 mW/cm² for 10 minutes (0.3 J/cm²) significantly increases:
- LOXL1, ELN, COL1A1, and COL3A1 gene expressions
- Synthesis of procollagen type I and elastin proteins
- Type III collagen and elastic fiber formation and crosslinks 2
Wound Healing
- Near-infrared wavelengths (800-830 nm) are most effective for wound healing, followed by red (630-680 nm) wavelengths
- These wavelengths promote:
- Reduction in inflammation
- Pain relief
- Restoration of function
- Wound repair and regeneration 4
Photobiomodulation at Appropriate Intensities
- When mimicking sunlight NIR intensity (30-35 mW/cm²), beneficial cutaneous effects are triggered
- The "sweet spot" for beneficial effects corresponds to the natural irradiance of the sun
- Morning NIR exposure may precondition the skin against upcoming mid-day UV radiation damage 3
Potential Adverse Dermatological Effects
Pain and Discomfort
- Pain described as "burning," "stinging," or "prickling" is commonly experienced during photodynamic therapy (PDT) using red light
- Pain typically peaks within minutes of exposure and levels out during treatment
- Face and scalp areas may be more susceptible to pain
- Large or ulcerated lesions are more likely to be painful 1
Pigmentation Changes
- Hyperpigmentation or hypopigmentation can occur in treated areas
- These changes usually resolve within 6 months
- Prolonged hyperpigmentation has been observed in some cases 1
Potential Carcinogenicity
- PDT has potential for promoting genotoxic effects including:
- DNA strand breaks
- Chromosomal aberrations
- DNA alkylation
- However, porphyrin molecules also possess antimutagenic properties
- After 25+ years of PDT use in humans, only two tumors have possibly been induced by this therapy 1
Heat-Related Effects
- In direct sunlight, skin temperature rises to about 40°C from absorbed infrared radiation
- Heat exposure can induce:
- Cutaneous angiogenesis
- Inflammatory cellular infiltration
- Disruption of dermal extracellular matrix
- Alteration of dermal structural proteins 5
Intensity Considerations
Importance of Proper Dosing
- The biphasic dose curve (Arndt-Schulz curve) establishes that:
- Irradiance below physiological threshold produces no beneficial effects
- Photo-inhibitory deleterious effects occur at higher irradiances
- The beneficial range corresponds to natural solar irradiance 3
Intensity vs. Duration
- Intensity appears more important than total fluence (dose) delivered
- The law of reciprocity does not always apply in photobiology
- High-intensity artificial light sources above solar IR-A irradiance threshold can lead to detrimental effects 6, 3
Safety Considerations
Eye Protection
- High-intensity light poses potential hazards to the eye
- Blue light (400-450 nm) could irreversibly damage photosensitive neurotransmitters in the macula
- Staff and patients should wear suitable filter spectacles during treatments 1
Skin Cancer Prevention
- UV radiation is the primary cause of skin cancer (65-90% of melanomas)
- Red and near-infrared light therapy should be used cautiously in patients with history of skin cancer
- Regular skin examinations are recommended for individuals receiving light therapy 7
Clinical Applications
Photodynamic Therapy
- 5-aminolevulinic acid (ALA) with red light PDT is effective for treating actinic keratosis
- Longer ALA application times (1-4 hours) enhance complete clearance of AKs
- Daylight PDT (using natural sunlight) is less painful but equally effective as ALA-red light PDT 1
Anti-Aging Applications
- Low-level red plus near-infrared LED light combination may provide effective treatment for photo-aged skin
- Treatment increases ATP production in human dermal fibroblasts 2
In conclusion, red and near-infrared light exposure offers significant therapeutic potential when used at appropriate intensities and durations. The key to maximizing benefits while minimizing risks lies in mimicking natural solar irradiance rather than using high-intensity artificial sources that exceed physiological thresholds.