Published Studies
The Subtlety of Photosensitivity among the sun shy Asians
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The Subtlety of Photosensitivity among the sun shy Asians. 

Verallo-Rowell VM. 
Oral Presentation/Abstracts Eighth Asia Pacific Environmental and Occupational Dermatology Symposium in cooperation with the Philippine Dermatological Society. October 2005. 
Theme: Clinical Dermatology in Asia 2005 and Beyond 
In 2002, the author proposed that melasma is often a photocontact dermatitis.  This was based on positive and relevant photopatch tests in 20 melasma compared to 20 non-melasma patients.  Sixty eight photoallergens (20 in the NACDG Photopatch tray; 13 plant, 24 fragrance from Chemotechnique; and 11 from SSLI), elicited positive photopatches in 9/20 melasma versus 1/20 non-melasma patients exposed to UVA light; 19/20 melasma versus 1/20 non-melasma patients exposed to Visible light; and 6/20 melasma versus 1/20 non-melasma patients exposed to Infrared light. Using Fisher’s Exact Test, relevant photocontact dermatitis was found statistically significant to UVA and Visible lights; not significant to Infrared Light1.  Relevant photocontact dermatitis presenting as melasma was proposed as due to low grade light exposures over time among the sun shy.
At the private clinic of the senior author from May 2004 to April 2005, on twenty sequential patients who presented for melasma, and consented to a photopatch test, a clinical and historical search for photosensitivity, followed by photopatch testing were done using Chemotechnique Trays of plants, fragrance and photoallergens; and SSLI sunscreen ingredients.
Clinical: All had subtle dyschromia or irregular pigmentation at the classic pattern sites of photodermatitis: V and nape of the neck, outer arms, with sparing of the areas under the chin, inner arms, eyelids, areas often covered by clothing, and a mild to moderate melasma.
Historical:  All are Asians who habitually avoid sun exposure to prevent the heat, sweating, brightness, feeling of general discomfort, and particularly the skin tanning from it.  When shown the irregular body pigmentation, all believed it was due to aging, not sun exposure.
None suspected photosensitivity, nor had itching, urticaria, vesicles, or redness.  Similar to the Singapore patients 2 who also avoid sun exposure, only 25% vs up to 100% in other studies 3,4,5 associated the onset, worsening, recurrence of the melasma with sun exposure.
All had multiple relevant positive photopatch test results.