Photopatch test method: influence of type of irradiation and value of day‐7 reading

Abstract

118 consecutive patients were photopatch tested with 5J UVA and 10mJ UVB. In addition, day 7 readings were taken. Testing with UVB and performing late readings conferred no advantage. The current recommendations of the British Photodermatology Group regarding photopatch testing remain the most recent guide to photopatch test methodology.

Photoallergy

“…Obtaining more than one reading after irradiation helps in the interpretation of results; positive reactions with a decrescendo pattern between the two readings are more likely to be phototoxic, and those with a crescendo pattern are photoallergic (71,72). There seems to be no additional benefit of later readings 7 days after irradiation (64 Table 3 Agents recommended for the European photopatch test baseline series and their suggested concentration and vehicle for testing (68).…”

“…Shorter wavelengths of UVB will likely cause erythema at doses below those required to trigger photoallergy, and there is no evidence to support a role for UVB in photopatch testing (59,64). UVA doses between 5 and 10 J/cm 2 , delivered using PUVA tube lights and, have been used in the photopatch testing (65).…”

Photoallergic Contact Dermatitis

“…59 It is important if possible to obtain readings at more than one time point after irradiation as interpretation of results is facilitated if pattern analysis can be undertaken. There seems to be no additional benefit of later readings 7 days after irradiation.…”

Celecoxib‐induced photoallergic drug eruption

“…Well‐known systemic photosensitizing substances include griseofulvin, phenothiazine and related compounds, sulfonamides, quinolone, diphenhydramine, thiazide diuretics, sulfonylurea hypoglycemics, NSAIDs (piroxicam, naproxen, benoxaprofen), and quinidine 11,12 . The mechanism involved in the pathogenesis of photoallergic contact dermatitis is thought to be a form of cell‐mediated hypersensitivity, and UV radiation is required both to induce and elicit the immune response 13 . In our patient, the symptoms developed promptly after the initiation of celecoxib treatment, suggesting that celecoxib was the precipitating agent.…”