Author: Dr Alison Bullen, Honorary Dermatology Registrar, Brisbane Skin, Brisbane, Queensland, Australia; Dr Shobhan Manoharan, Dermatologist and Director, Brisbane Skin and Westside Dermatology, Brisbane, Queensland, Australia. DermNet NZ Editor-in-Chief Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Update of an original article (2008) by Dr Marius Rademaker, Dermatologist, Hamilton, New Zealand. March 2019.
The 2019 update of this article was supported by Johnson and Johnson Australia, distributors of the Neutrogena Visibly Clear™ Light Therapy Acne Mask in New Zealand and Australia. Sponsorship does not influence content.
Laser and light therapy are used to treat mild active acne and acne scarring [1,2]. Laser and light therapy provide useful options for patients with acne that persists despite medical therapy, who experience side effects to a medication or who have difficulty adhering to medical treatments.
Image credits: 1. Westside Dermatology; 2. Brisbane Skin; 3. Dr Shobhan Manoharan, Brisbane Skin
Light therapy uses particles at a non-thermal intensity to alter the biological activity of the skin at different levels. Low-level light therapy is usually applied via light-emitting diodes (LED) as red or blue light. Varying wavelengths of light penetrate to different depths within the skin, with wavelengths between 390 and 600 nm reaching superficial layers; wavelengths of 600 to 1100 nm penetrate the deeper layers. Low-level light therapy is safe, and patients experience minimal discomfort. It typically involves exposing the skin affected by acne to either continuous or intense pulsed light on several occasions and often in conjunction with topical or oral acne medications.
Blue light therapy has wavelengths 475–545 nm and penetrates approximately 0.3 mm into the skin. Propionibacterium acnes (also known as Cutibacterium acnes), the main bacteria involved in the pathogenesis of acne vulgaris, produce large amounts of intracellular porphyrins, the most abundant of which has a peak absorption at 415 nm. Blue light excites these porphyrins, leading to the production of reactive oxygen species and subsequent bacterial destruction. It also has anti-inflammatory effects through modulation of cellular inflammatory mediators.
Red light (600–650 nm) activates porphyrins with less intensity than blue light. However, it penetrates the skin 1–2 mm deeper than blue light . Low-level light therapy using red LED treatments reduces inflammatory mediator expression from macrophages and cause a reduction in neutrophils, interleukins and matrix metalloproteinase in acne animal models. It may also inhibit keratinisation and reduce skin barrier damage. Red light therapy reduces the activity of acne vulgaris by accelerating wound healing and reducing the inflammatory response.
Blue-red light uses low-level light therapy in both blue (415 nm) and red (680 nm) wavelengths. Multiple studies have shown it is well tolerated and effective through a reduction in inflammatory and non-inflammatory acne lesions and is superior to blue light alone . The mechanism is thought to be synergistic in applying both the antibacterial and anti-inflammatory actions of both wavelengths of light acting at different depths within the skin. It is safe in pregnancy. Some patients may experience a deterioration of their acne with blue-red light therapy, and side effects of blue-red light can include dryness, itch, a rash and headaches.
Home light therapy devices consist of wearable masks that use low-level light therapy as an LED-based, non-thermal, non-ablative treatment. Currently approved devices on the market use blue-red light, and are approved for mild to moderate facial acne. These devices are typically smaller than in-office LED devices and thus may require extended treatment sessions for a therapeutic effect. They have been shown to reduce inflammatory and non-inflammatory acne lesion counts and reduce the size and sebum production of sebaceous glands . A recent trial compared a blue-red light therapy mask with and without topical salicylic acid against topical benzoyl peroxide for mild to moderate acne vulgaris. They found a 24.4% improvement in inflammatory lesions and 19.5% improvement in non-inflammatory lesions in patients using the light mask, concluding this to be a safe and effective therapy for mild to moderate acne treatment .
Photodynamic therapy (PDT) is an effective treatment for acne and can significantly decrease its severity with regular treatments. PDT involves the application of a photosensitiser before exposure to a light source. The effect of the light is amplified by the photosensitiser. The most common photosensitisers are aminolevulinic acid (ALA) and methylaminolevilunate (MAL). Indocyanine green (ICG) and indole-3-acetic acid can also be used.
Common light sources used for photodynamic therapy include:
The optimal light source, photosensitiser and incubation time are unclear. The evidence that PDT is useful in the treatment of acne is positive but limited .
PDT utilises a photosensitiser taken up by the pilosebaceous unit and undergoes metabolism to cause oxidative stress and free radicals, which destroys Propionibacterium acnes and modulates the sebaceous gland .
Side effects of photodynamic therapy include:
Intense pulsed light (IPL) devices emit a spectrum of wavelengths between 400 and 1200 nm. This allows multiple chromophores to be activated with one light exposure. Pulse duration, wavelengths and pulse intervals can all be adjusted with cut-off filters to enable tailoring of treatments to a patient’s specific skin type and condition. To date, there is conflicting evidence regarding its effectiveness in treating acne. IPL in combination with a photosensitiser is superior to IPL alone .
Side effects of IPL can include:
The contraindications to IPL treatment are:
IPL has a photodynamic effect. UV and visible light are absorbed at peak wavelengths by porphyrins that are produced by Propionibacterium acnes. This has a bactericidal effect by causing the release of reactive oxygen species. It may also work by selective photothermolysis of blood vessels supplying sebaceous glands, reducing sebum secretion rate. IPL can be used with a topical photosensitiser which accumulates in the sebaceous gland. Light activation of the photosensitiser causes the destruction of the sebaceous glands .
The 585–595 nm pulsed dye laser (PDL) uses an organic dye as the laser solution and targets oxyhaemoglobin to cause heating and photothermolysis of dilated vessels within inflammatory acne lesions. The mechanism of action is likely multifactorial. PDL potentially also has a photochemical effect on porphyrins produced by Propionibacterium acnes causing a phototoxic effect . Studies have not shown a reduction in sebum production with its use; however, upregulation of potent anti-inflammatory mediator TGF-beta and inhibition of CD4+ T-lymphocyte mediated inflammation suggest an anti-inflammatory mechanism . PDL has been used predominantly in the treatment of vascular skin lesions and atrophic scarring, and it is increasingly being used in the treatment of acne vulgaris, particularly for patients with acne-induced facial erythema.
PDL is often used in conjunction with topical photosensitisers. It can improve the severity and number of inflammatory lesions in acne. The side effects of PDL have somewhat limited its usefulness. These include:
Infrared lasers can penetrate deeply into the dermis to target water within the sebaceous gland. This is thought to cause thermal coagulation of the sebaceous gland, arrest sebum production and thereby reduce acne. 1450 nm diode and 1540 nm erbium glass lasers have been studied for acne treatment.
The 1540 nm erbium glass laser improves inflammatory acne through non-selective heating of sebaceous glands. Small studies have shown 68–82% reduction in acne lesions with the effects sustained at 24 months follow-up . This particular laser has very few reported side effects.
The 1450 nm diode laser heats the upper mid-dermis, causing thermal coagulation of the sebaceous lobule and follicular infundibulum, reducing the activity of sebaceous glands . Some studies have shown a reduction in sebum production while others have not. It does appear to reduce lesion counts in several small trials; the considerable side effect profile of significant pain and discomfort, dryness and erythema have led to this laser falling out of favour with many dermatologists.
The neodymium-doped yttrium aluminium garnet (Nd:YAG) is a crystal used most commonly in a 1064 nm laser that can penetrate deeper layers within the dermis causing diffuse dermal heating while limiting epidermal damage . Although its mechanism is not entirely defined, it probably treats acne by reducing inflammation and sebum production. This laser has been more extensively studied in the treatment of acne scarring; however, there is emerging evidence for its use in the treatment of active acne.
Patients usually undergo several sessions of Nd:YAG laser treatments at two-week intervals. It reduces inflammatory acne lesion counts, sebum output and inflammatory cytokines and cells in treated skin. The Nd:YAG laser is a safe, useful treatment for active acne, with potential side effects including mild transient erythema, skin tenderness and dryness.
Nd:YAG appears to be a useful treatment modality for active acne vulgaris, although further high-quality studies are still required. Treatments are safe, with possible side effects including skin redness, tenderness and dryness .
The potassium titanyl phosphate (KTP) 532 nm laser emits green light pulsed laser, penetrating deeper than blue light, and is used predominantly to treat telangiectasia and rosacea. It activates porphyrins which target Propionibacterium acnes to cause thermal damage to sebaceous glands . Limited data support its use in active acne; however several small studies have shown a transient reduction in acne lesion count (21–36%) . The side effects include transient crusting, oedema and erythema.
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