Five years experience of photopatch testing in 50 patients

Pramila A Kanchan, Shrutakirthi D Shenoi, C Balachandran

 Department of Skin and STD, Kasturba Medical College and Hospital, Manipal - 576 119, Karnataka, India

Correspondence Address:
Shrutakirthi D Shenoi
Department of Skin and STD, Kasturba Medical College and Hospital, Manipal - 576 119, Karnataka
India

Introduction

Photopatch test serves as a tool to identify photosensitisers. Until the early 1980′s, photopatch testing was not standardised. The procedure varied between dermatologic centers, among different countries and internationally. The first attempt to standardise the method was initiated by the Scandinavian Photodermatitis Research group in 1982. The purpose of this study was to detect the common photosensitisers in patients presenting with clinical features suggestive of photodermatitis.

Materials and Methods

Fifty patients (29 males, 21 females) aged between 17 and 75 years, from January 1994 to August 1999 were patch tested with Scandinavian photopatch series, obtained from Chemotechnique Diagnostic AB Sweden which was applied in duplicate over the back. After 48 hours the patches were removed and the right side exposed to 15J/cm2 of UVA, while the other side was covered with opaque thick paper. Both irradiated and non-irradiated sites were evaluated after 48 and 72 hours. 1 + or > reactions at irradiated sites alone, were considered significant for contact photoallergy.

Results

Ten out of 50 patients (7 males, 3 females) showed positive photopatch test reactions. [Table - 1] shows the antigens of the photopatch test series and the number of positive cases.

Discussion

In the Scandinavian multicentric photoptach study musk ambrette and PABA were the leading photosensitisers.[1] In a study from Singapore[2] musk ambrette, chlorpromazine and promethazine were the frequent photoallergens. In our study musk ambrette, chlorpromazine and promethazine showed positive reactions in 4% each, while balsam of peru, triclosan, diphenhydramine, fentichlor and perfume mix in 2% each. In a similar study[3] conducted from 1991 - 1994 in our department, perfume mix was the leading photosensitiser [Table - 1]. Musk ambrette is a synthetic fragrance fixative used in food and cosmetic industries. Chlorpromazine usually causes photocontact dermatitis, but on systemic exposure phototoxic dermatitis may develop. Promethazine can produce phototoxic and photoallergic reactions. Cross sensitivity is known to occur with chlorpromazine and promethazine.[4]

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