Introduction

What’s your body’s largest organ? As you’re reading this, chances are you guessed correctly: the skin. Its importance is often underestimated despite its pivotal role as our primary barrier against harmful external elements and, justifying our attention to aesthetics, our physical interface with the world around us. If you’re conscious of skin health, appearance or specific skin concerns, you may have encountered the emergence of red light therapy, proposed as a safer, painless and more convenient option than other well-established skin treatments; red light therapy involves repeated skin exposure to low-level red and near-infrared light.¹ But if you search for the term online, you’ll likely be met with an avalanche of companies eager to sell you their latest red light therapy devices or services - and for a hefty price tag. 

From skin rejuvenation to wound healing, the applications of red light therapy have penetrated both the beauty and medical industries, recently expanding beyond the confines of dermatology clinics to find a place in at-home skincare regimens.¹ With many supposed benefits circulating the internet, it takes time to discern scientifically backed findings from marketing statements. How accurate are these claims - and is red light therapy worth your time and money? Read on to find out what science has to say.

Origins and uses of red light therapy

In the late 1960s, Hungarian physician Endre Mester saw improved hair growth and wound healing in rats while experimenting with low-energy wavelengths of red light.² But could it bring us the same benefits to humans? 

Traction for red light therapy was gained by pursuing this question following NASA’s exploration of its use in supporting wound healing in astronauts. Its potential applications for the skin have now broadened, with much interest in its ability to address various skin concerns. Common examples include:^{1, 3}

• Wrinkles
• Sagging skin
• Acne
• Scarring
• Burns
• Sun damage  
• Pigmentary disorders (e.g. vitiligo)
• Skin conditions such as psoriasis, eczema, and rosacea 

Medical applications beyond the skin are also being explored; in fact, more than 40 clinical trials are currently in progress for its use in various medical conditions.^{3, 4} Perhaps according to its numerous (over 100) potential applications, red light therapy takes on around 60 different titles in scientific literature.³ The most common of these include:

• Low-level laser (light) therapy (LLLT)
• Low-power laser therapy (LPLT)
• Phototherapy
• Cold laser therapy 
• Soft laser therapy
• Non-thermal LED light

Although the term red light therapy is often used interchangeably with photobiomodulation (PBM), red light is, in fact, a type of PBM therapy. As reflected by its name, PBM involves using specific wavelengths of red or near-infrared light to modulate a range of aesthetically and medically beneficial biological processes in our cells.³

Low-level lasers, filtered lamps, LED, or a combination of lasers with the latter two light sources may be used. LEDs are becoming the preferred choice of light source over lasers due to them being both non-ablative, meaning that they don’t remove the outermost (epidermal) layer or deeper (dermal) layers of the skin, and non-thermal (they don’t generate heat).¹

How does red light therapy work?

As mentioned earlier, red light works via photobiomodulation. Low-energy photons (light particles) released from the light source are absorbed by the skin and ‌ our cell’s powerhouse: the mitochondria. These mitochondria are where energy is generated. Specific wavelengths of red and near-infrared light can increase mitochondrial energy.¹

Given the role of poor mitochondrial function in age-related issues and many disease processes, red light therapy's wide-ranging benefits might be explained by its positive effect on mitochondrial activity. While we don't fully understand how these light wavelengths interact with our cells to support photobiomodulation, it's believed that these interactions contribute to the treatment's beneficial effects on the skin.³

What does red light therapy do for your skin?

The increase in mitochondrial activity induced by red light initiates a cascade of events stimulating various biological processes.⁵ These include:

• Increased collagen production 
• Increased generation of growth factors 
• Reduced inflammation 

These processes, among others, may contribute to skin rejuvenation and improving existing skin conditions, as described below.

Reducing signs of skin ageing

Collagen is the body's main structural protein. Its age-related decline in production contributes to wrinkles and sagging skin formation.⁵

Red light therapy may elevate collagen synthesis by increasing fibroblast activity. Fibroblasts are cells that form part of your connective tissue and are responsible for generating collagen.⁶ Collagen production is also stimulated by activating a wound-healing response, in which fibroblasts play an essential role. Many traditional forms of skin rejuvenating laser treatments work based on intentionally wounding the skin’s uppermost layers to induce this response (e.g. via previously mentioned ablative techniques) and promote collagen production. LED-based red light therapy triggers the same process without thermal damage.¹

Scientific studies have demonstrated the collagen-boosting effects of red light in tissue and live animal models since the late 1980s, but this has also more recently been shown in humans.¹ In a study of 136 people receiving red light therapy for ‌30 sessions (twice a week), significant improvements in the complexion, smoothness, collagen content and overall skin feeling were found following red light therapy.⁷

Acne

Red light may reduce acne-causing inflammation by helping regulate specific immune cells' activity. It can also modulate sebum production (the oily substance released from our pores) by potentially reducing the size of our sebaceous glands, which are responsible for making this sebum. ⁸ 

Several studies have demonstrated the effectiveness of red light in treating acne, either alone or in combination with blue light (which may have antibacterial properties), to produce improved effects. ^{1, 8} For example, a 2017 study testing simultaneous low-level blue and red light therapy reported a reduction in the number of acne lesions and improved overall skin appearance in people with mild-to-moderate acne, compared to treatment with benzoyl peroxide (a standard topical acne treatment).⁹ 

Psoriasis

Due to its anti-inflammatory effects, red light therapy may help improve psoriasis's appearance - an inflammatory autoimmune skin disease.¹⁰ Demonstrating this, patients with treatment-resistant psoriasis who used red light therapy for two 20-minute sessions throughout 4 to 5 weeks achieved a 60-100% clearance rate with high satisfaction rates and no significant side effects.¹¹

Wound healing and scar reduction

While increased collagen synthesis is desirable for diminishing the signs of ageing, an imbalance between collagen production and its degradation can lead to scarring, including hypertrophic and keloid scars.¹ Fortunately, while red light therapy can stimulate collagen production, it can also reduce it when the protein is present in excess - as it is during wound healing and scar formation.¹² It can, therefore, help to restore the appropriate balance of collagen generation, which may decrease scar thickness and accelerate the healing of wounds (supported by its anti-inflammatory effects) while supplementing collagen-depleted areas of the skin.¹³

How to use red light therapy

Professional settings versus at-home devices

Red light therapy sessions may be offered at dermatology clinics and, increasingly, spas or wellness centres. Within this setting, red light therapy can be combined with other treatments, such as microneedling, to enhance potential benefits.¹ Red light devices intended for home use (such as face masks, panels, desk lamps and handheld wands) employ lower-level wavelengths and don't penetrate as deeply into the skin as those used in professional settings. The reported benefits from these lower-power devices need more scientific backing, like the studies discussed, that form the basis of in-clinic technology. As a result, they may produce a different level of improvement while likely requiring more frequent or longer-term use to achieve desired effects.

What are the possible risks and side effects of red light therapy?

Red light therapy is considered a safer, painless, non-ablative and non-invasive alternative to more intensive skin-improving therapies, such as topical retinoic acid (vitamin A), chemical peels, dermabrasion or laser resurfacing. It also rarely requires downtime or post-treatment care and is safe for all skin colours and skin types.^{1, 14} Unlike the high-energy ultra-violet (UV) light from the sun or tanning beds that can cause cancer, the light used in red light therapy does not damage the skin and is therefore safe for regular use.^{1, 7}

If used as directed, for the instructed duration and on a short-term basis, it isn’t associated with any side effects besides mild hyperpigmentation in some cases.^{7, 14}  When misused, e.g., longer than 30 minutes without professional supervision or because of issues with the device, incidents of burns or blistering have been reported. Although an LED-based light source is less harmful than traditional lasers used for red light therapy, it’s advised to wear appropriate eye protection if you’re targeting your face and neck. 

Additionally, people with skin conditions that may heighten sensitivity to certain types of light (e.g. lupus), those taking photosensitising medication and those with open wounds should consult a doctor before attempting red light therapy. Even without such skin conditions, it’s well-advised to talk to your dermatologist for pre- and post-treatment care before starting red light therapy.

Summary

Red light therapy is a promising skincare frontier, offering a non-invasive approach with multifaceted benefits. Its efficacy in stimulating collagen production, reducing inflammation, and promoting wound healing underscores its potential for addressing various skin concerns. While scientific evidence supports its positive impact, there is a call for higher quality and consistent studies to substantiate the promising claims regarding its skin benefits and provide further insight into its underlying mechanism. Considerations for safe and effective use, such as choosing the correct device at the range of wavelengths for your skin concern and consulting with your dermatologist, play a crucial role in optimising outcomes. A promising future for red light therapy in skin health is evident, with ongoing studies pointing towards the continued expansion of its applications and a deeper understanding of its potential benefits.