True Photoallergy to Sunscreens is Rare Despite Popular Belief

Tatyana Shaw; Brenda Simpson; Brittney Wilson; Holly Oostman; David Rainey; Frances Storrs

Disclosures

Dermatitis. 2010;21(4):185-198. 

In This Article

Methods

This study, approved by the institutional review board, was conducted in a specialty contact dermatitis clinic between July 2007 and January 2009 and was funded by a grant from the American Contact Dermatitis Society. The objective of the study was to investigate whether patients who identify themselves as allergic to sunscreens have relevant allergic or photoallergic contact dermatitis from sunscreens, based on patch testing and photopatch testing results.

Patients (18 years of age or older) who identified themselves as "allergic" or as "having a reaction" to sunscreens were recruited from Oregon Health & Science University, Portland Veterans Affairs Medical Center, and community dermatology clinics. As patients contacted the clinic, the patch testing and photopatch testing were discussed with them. Testing involved at least 4 days of participation from patients; patients spent some of the time in a rather confined warm box that administered UV light. The majority of patients interested in participating could not commit several hours to such a time- and laborintensive study. Of 27 patients who contacted the clinic initially, only 11 agreed to complete the testing involved. Although there was a $50 (US) compensation for completion of the testing, the participants found it difficult to undergo 4 days of rigorous testing, and many struggled to fulfill the study requirements.

All patients who participated in the study filled out a questionnaire (shown in Figure 1) detailing their reactions to sunscreens, the onset and duration of their reactions, their family history, and their history of atopy.

Figure 1.

Questionnaire

All 11 patients were patch-tested with the 65 allergens on the North American standard tray, 36 allergens on our supplemental tray, a 28-allergen sunscreen tray (see Table 1 ), and any relevant personal sunscreens. The North American standard tray allergens were those listed in the 2005–2006 patch-test results reported by the North American Contact Dermatitis Group and were obtained from Chemotechnique Diagnostics (Malmö, Sweden).[66] The allergens on the supplemental tray were obtained from various sources and were designed to test for regional causes of allergic contact dermatitis.

The manufacturers of the sunscreen chemicals are listed in Table 1 . Because we were unable to obtain the individual sunscreen ingredient Mexoryl SX, we tested with an entire product, Anthelios SX, which the manufacturer generously provided. Tinosorb S and Tinosorb M are not approved for use in the United States; however, they have been used in Europe and were recently approved for use in Canada. Owing to the geographic proximity of Oregon to Canada, our patients could have obtained sunscreens in Canada although no patients specifically reported having done so.

Patch testing was done with a standardized technique with 8 mm Finn Chambers (Epitest Ltd Oy, Tuusula, Finland) on Scanpor tape (Norgesplaster Alpharma A/S, Vennesla, Norway) by dispensing approximately 3 mm segments of allergen on each chamber.[66] To dispense a liquid allergen, the filter paper was wetted with the allergen, evaporated partially, and then applied to the patient's back.

Initially, patients were photopatch-tested to determine their minimal erythema dose (MED) for both UVB and UVA spectra according to the protocol described by Dr. Vincent De Leo.[67] Both UVB and UVA were tested to determine if any of the patients had reduced MED values that could point to an internal photosensitivity. Only UVA was used for the photopatch testing. That same day (day 1), the sunscreen allergens were placed into Finn Chambers and applied directly to normal uninvolved skin of the back in duplicates for patch and photopatch testing. At 24 hours (day 2), the photopatches were removed, and patients were assessed for any skin reactions. On the same day, reading was done to determine the patient's MED. As none of the patients had abnormal UVA MEDs, one set of photopatches was irradiated with UVA (10 J/cm2). Immediately after UVA exposure, the photopatch tests were read to determine immediate-type hypersensitivity reactions; the patch areas were then covered with opaque tape material. The next reading was at a further 24 hours (day 3), and the final reading was at 5 to 7 days. The patients were instructed not to get their backs wet for the duration of the patch testing and photopatch testing and through the day of the final reading.

The North American standard tray allergens and the supplemental tray allergens were also placed on day 1 of testing. Those patches were removed and read 48 hours later (day 3), and the final reading was done on day 5 or day 7.

Five patients reported immediate reactions to sunscreens on the questionnaire shown in Figure 1. In addition to being patch- and photopatch-tested as described above, three of these five patients were also tested for contact urticaria from common contact urticaria–inducing substances (resorcinol 1% in petrolatum [pet], cinnamic aldehyde 1% pet, benzoic acid 5% pet, sorbic acid 2% pet, sodium benzoate 5% pet, and white 100% petrolatum), sterile water (as a negative control), histamine (as a positive control), and the patients' personal sunscreens. The allergens were applied to the 8 mm Finn Chambers and taped to the volar forearms with Scanpor tape. These patches were initially read 30 minutes after occlusion. If the test sites were negative, then the patients underwent 8 mm scratch-testing with sterile disposable needles (ALK-Abello, Horsholm, Denmark) to re-apply the contact allergenic substances for another 30 minutes.

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