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Macrene Alexiades-Armenakas

Department of Dermatology, Yale University School of Medicine, New York, NY, USA

21.1	Introduction	400
21.2	Acne Treatment with PDT	400
	21.2.1	Background	400
	21.2.2	Light Treatment Alone	400
	21.2.3	Systemic ALA with Light	401
	21.2.4	Topical ALA and Red Wavelengths	401
	21.2.5	Topical ALA and Blue Light	402
	21.2.6	Topical ALA and LP PDL	402
	21.2.7	Topical ALA and IPL	405
	21.2.8	Mechanism of PDT in Acne	405
	21.2.9	Conclusions: PDT for Acne	405
21.3	PDT Photorejuvenation	406
	21.3.1	Topical ALA and Blue Light	406
	21.3.2	Topical MAL and Red Light	406
	21.3.3	Topical ALA and LP PDL	407
	21.3.4	Intense Pulsed Light-Mediated PDT	407
	21.3.5	Conclusions: PDT Skin Rejuvenation	408
21.4	PDT for Hair Removal	409
	21.4.1	Conclusions: PDT for Hair Removal	411
References		411

Gurpreet S. Ahluwalia (ed.), Cosmetic Applications of Laser and Light-Based Systems, 399-414,

21.1 I ntroduction

Photodynamic therapy (PDT) is a century-old treatment for neoplastic conditions, which most recently has evolved to treat acne and photoaging. PDT is often used for therapeutic challenges; for example, it is currently being tested by the author for the removal of unpigmented hair. An oxygen-dependent reaction between a photosensitizer and light, PDT has employed various photosensitizers and light sources to target distinct cutaneous conditions and tissues [1,2]. Systemic porphyrins, such as hematoporphyrin were the earliest photosensitizers used, but associated with the unwanted side effect of prolonged photosensitivity [1]. Over the past two decades, topical photosensitizers, such as 5-aminolevulinic acid (ALA), and more recently, methylated ALA (MAL) have been developed and have become the most common photosensitizers for dermatologic use. Light wavelengths are chosen according to the porphyrin absorption spectrum: blue wavelengths corresponding to the Soret band, the largest 400 nm peak, and additional wavelengths corresponding to the Q bands in the 500-700 nm range. Broad-band blue light, and red lasers, and light have been studied extensively. The FDA approved indications include topical ALA and blue light since 1999, and topical MAL and red light since 2006. The long-pulsed pulsed dye laser (LP PDL, 595 nm) and intense pulsed light (IPL) are the most recent light sources with favorable results in PDT, with the advantages of greatly minimizing side effects, without compromising efficacy for the treatment of actinic keratoses, photoaging, and acne vulgaris [1,2]. Areas of further research include PDT for the removal of unpigmented blonde or gray hair, a current challenge in dermatology.