What is photo dynamic therapy (PDT)?

Propionibacterium acnes growing in pores produces a fluorescent orange glow when illuminated by ultraviolet light

Photo dynamic therapy (PDT) is the generic name for treatments that use specialized medications, called photosensitizers, to increase the effectiveness of a light based treatment. PDT is not only used for acne treatments, it is also employed as a cancer treatment to improve the effectiveness of laser-based destruction of cancerous cells. In acne treatment, there are three main photosensitizers used to improve the efficacy of the therapy. These medications are: MAL (methyl aminolevulinate) , ALA (aminolevulinic acid) and LA (levulinic acid). MAL and LA are generally used with red light sources and are more commonly used against cancer and skin disease. ALA is utilized in most acne treatments and is used with blue light therapy. Most research on the subject indicates that PDT is more effective than light therapy alone in the treatment of acne. PDT can be performed using all of the major light therapy systems (LED Blue/Red, IPLand Laser Systems).

How does PDT work?

Treatment with ALA Leads to Increased Levels of Porphyrin (Hamblin)

The photosensitizers used in PDT are designed to increase the production of pigments and other molecules that absorb the light being used in the treatment. ALA stimulates the production of porphyrin, which improves the anti-bacterial capability of blue light treatment. MAL is used with red light therapy, although it is more commonly used as part of a skin cancer treatment than acne therapy. ALA and LA are starting compounds in the biosynthesis of porphyrin. Treatment with these medications prior to therapy increases the amount of porphyrin in Propionibacterium acnes bacteria and therefore increases the killing efficacy of blue light phototherapy. The increased levels of porphyrin generate elevated levels of anti-bacterial reactive oxygen molecules during treatment, which kills more bacteria than light therapy alone. In addition to the antibacterial action, this type of treatment has been shown to temporarily decrease sebum production as well. Treatment with these photosensitizers can also increase the levels of endogenous porphyrins in the skin. Because of this, PDT is also used in treatments that target the skin itself and hair follicles. Some dermatologists even advocate using ALA-PDT to treat sebaceous hyperplasia (enlarged sebaceous glands) and other conditions. However, that approach is not highly targeted and can lead to a lot of indiscriminate skin damage. There are much more effective laser systems available for those types of treatment, and they generally produce less collateral damage.

Is PDT an effective treatment for acne?

P. acnes Bacteria Fluorescing in Follicles of Acne Patient Under UV Illumination

Photo dynamic therapy has been shownin numerous research articles to decrease bacterial levels in the skin and control the symptoms of acne better than light therapy alone. The most common PDT treatment for acne uses Aminolevulinic acid (ALA, Levulan) as the photosensitizing agent, although this is technically an off-label use. The company that markets Levulan withdrew their application to have ALA-PDT certified by the FDA for acne treatment after their phase II clinical trials showed disappointing results. Nonetheless, it remains a popular technique for many dermatologists and has mixed reviews by acne patients who have undergone PDT acne treatment. It is important to keep in mind that PDT, like most light therapies, provides only temporary benefit and treatment must be repeated regularly to realize significant results. Because PDT requires the careful application of a photosensitizer and controlled light exposure, effective photo dynamic therapy for acne can become quite expensive and time consuming. There are also potential risks associated with the photosensitizers themselves, such as allergic reactions, hypersensitivity to sunlight, redness and inflammation. In summary, while PDT can be an effective acne treatment, many people may prefer frequent blue light therapy over PDT because of the decreased risk of side effects. And, if you are going to spend $600+ on PDT, you could get a nice light therapy system for at home use instead.

How and where is PDT administered?

ALA Treatment Causes Porphyrin to Accumulate in the Sebaceous Gland (Sakamoto)

Because Levulan (ALA) and the other photosensitizers are prescription medications, photo dynamic therapy is generally available only in a dermatology or cosmetic surgery clinic. This is also necessary because the treatment has a high risk of side effects if applied improperly.

How much does PDT cost?

ALA is the Primary Photosensitizer Used in PDT Acne Therapy

Generally photo dynamic therapy costs between $100 and $350 per session. Most dermatologists recommend at least four sessions. But keep in mind that the results are rarely permanent and continued control over acne symptoms will likely require continued treatment. So generally speaking, a PDT starter package of four treatments will cost in the vicinity of $700.

Popular Systems

Levulan (Blue Light Therapy)
Metvix (Red Light Therapy)

Before and after PDT pictures of acne patients

Before and after pics of patients undergoing PDT acne treatment can be found here.

References and Sources

Topical ALA Photodynamic Therapy for the Treatment of Acne Vulgaris.
Hongcharu, et al. 2000. For article abstract, click here.
Photodynamic therapy for acne vulgaris: A critical review from basics to clinical practice.
Sakamoto, et al. 2010. For article abstract, click here.
The practicalities of photodynamic therapy in acne vulgaris.
Taylor, et al. 2008. For article abstract, click here.
Laser and Non-laser Light Sources for Photodynamic Therapy.
Brancaleon, et al. 2002. For article abstract, click here.

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In Depth: Photo Dynamic Therapy (PDT)