Sir:
Over recent decades, many permanent hair removal (epilation) techniques have been tested and used with increasing frequency but with mixed results, particularly long-term results.1 There are at least three rationales for testing topical photodynamic therapy as an alternative to lasers in unwanted hair: (1) it has an experimentally demonstrated phototoxic effect on hair structures2; (2) its mechanism of action is independent of the concentration of eumelanin in the skin, and therefore independent of skin type and hair color; and (3) it has a very low frequency of long-term side effects.
This prospective, multicenter, open, uncontrolled study was carried out in Italy according to the Declaration of Helsinki (sixth revision, 2008). After consecutive enrollment, subjects affected by idiopathic hirsutism or hypertrichosis were asked to perform a hot wax epilation and were eventually administered photodynamic therapy (as described elsewhere)3 in multiple sessions.
Seventy-five women (age range, 26 to 76 years) affected by idiopathic hypertrichosis and 34 women (age range, 19 to 47 years) affected by idiopathic hirsutism successfully completed the study. A total of 183 areas were treated (Table 1). Digital photographs were archived and analyzed by means of DDAX software (Biomips Engineering SRL, Siena, Italy), and hairs were counted by two independent assessors.
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Table 1: Number of Sites and Type of Prodrug Application in 109 Patients
As detailed in Table 2, approximately 43 percent of all treated areas showed 75 percent or more hair reduction at 12 months, whereas approximately 13 percent featured regrowth of more than 25 percent of hairs already at 3 months. Similar findings were confirmed when considering various subgroups (hypertrichosis, hirsutism, hypertrichosis, and/or hirsutism with dark and/or light hair). No significant differences were found between anatomical regions, skin type, type of prodrug, and number of treatment sessions (data not shown). No long-term side effects were registered.
Table 2: Number and Percentages of Treated Areas of Hair Reduction at Follow-Up Visits*
Besides a 1995 abstract that reported mixed results on photodynamic therapy for 11 hirsutism subjects,4 the present study endorses topical photodynamic therapy as an effective option for the treatment of unwanted hair. Our results show that the effectiveness of photodynamic therapy is similar to that obtained by means of lasers; however, wide differences in study designs and outcome measures make an accurate comparison difficult. The absence of long-term side effects, in particular, hyperpigmentation and scarring, has to be considered another major achievement given the mostly cosmetic aim of the treatment. It should also be noticed that, as expected, results were independent of skin type or hair color.
Given the lack of specific studies, the mechanism of action of photodynamic therapy epilation can only be guessed. It is likely that a cytotoxic effect of photodynamic therapy on cells belonging to the hair bulge and papilla may be eventually accompanied by the release of mediators, such as interleukin-1 and tumor necrosis factor-α,5 capable of inhibiting hair growth and secreted by either keratinocytes or immune cells recruited by photodynamic therapy–induced local inflammation. The actively growing (anagen) phase of the hair cycle may be the most sensitive to the photodynamic effect; this assumption is indirectly confirmed by the higher number of treatment sessions needed to achieve the same results in skin areas characterized by a low density of anagen hair (e.g., legs) with respect to high-density areas (e.g., face).
Claudio Comacchi, M.D.
Italian Group of Radiofrequencies and Photodynamic Therapy, Florence, Italy, Italian Hi-Tech Network in Dermatologic Sciences, Milan, Italy
Pier Luca Bencini, M.D.
Italian Hi-Tech Network in Dermatologic Sciences and, Institute of Surgery and Laser Surgery in Dermatology, Milan, Italy
Michela Gianna Galimberti, M.D.
Italian Group of Radiofrequencies and Photodynamic Therapy, Florence, Italy, Italian Hi-Tech Network in Dermatologic Sciences, Milan, Italy
Pietro Cappugi, M.D.
Daniele Torchia, M.D., Ph.D.
Italian Group of Radiofrequencies and Photodynamic Therapy, Florence, Italy
DISCLOSURE
The authors have no financial interest to declare in relation to the content of this article. No outside funding was received.
REFERENCES
1. Wanitphakdeedecha R, Alster TS. Physical means of treating unwanted hair. Dermatol Ther. 2008;21:392–401.
2. Divaris DX, Kennedy JC, Pottier RH. Phototoxic damage to sebaceous glands and hair follicles of mice after systemic administration of 5-aminolevulinic acid correlates with localized protoporphyrin IX fluorescence. Am J Pathol. 1990;136:891–897.
3. Mori M, Campolmi P, Mavilia L, Rossi R, Cappugi P, Pimpinelli N. Topical photodynamic therapy for primary cutaneous B-cell lymphoma: A pilot study. J Am Acad Dermatol. 2006;54:524–526.
4. Grossman M, Wimberly J, Dwyer P, Flotte T, Anderson RR. PDT for hirsutism (Abstract). Lasers Surg Med. 1995;17(Suppl 7):44.
5. Ortel B, Shea CR, Calzavara-Pinton P. Molecular mechanisms of photodynamic therapy. Front Biosci. 2009;14:4157–4172.
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