Effect of dark test‐substance pigmentation on skin perfusion assessments and effect of test technique on balsam of Peru patch‐test results

Abstract

13 balsam of Peru (Myroxylon Pereirae) patch-test-positive subjects are re-tested with 25% balsam of Peru in petrolatum and with serial doses printed on polyester squares. All substances are applied with tape strips for 3, 6, 24 (1 day [D]), 48 (2D), 72 (3D) and 96 h (4D) on each subject and for 96 h (4D) with plastic foils. Tests are followed visually and with perfusion assessments from 3 h to 9 days. Results show that pigment remnants following detachment of patches affect perfusion assessments. Such effect due to pigment is supported by readings of patch tests through the petrolatum test substance while applied with transparent foils. For most reactions, good agreement is observed between the assessment techniques when peak assessment values of reactions are compared. There is inter-individual variation in perfusion with identical tests. With the petrolatum test substance, increased visible reactivity was observed when the application time was extended up to 24 h (1D), while extension of application time increased perfusion in most cases except for an extension from 24 (2D) to 48 h (4D) where decreased perfusion resulted in most cases. Dose and application time did not affect the timing of highest reactivity of reactions in most cases.

Effect of test techniques on perfusion of neomycin sulfate patch tests

“…For neomycin sulfate, that the highest value was detected at the same time with both reading techniques may be explained by either a slower increase in perfusion, or an earlier visible tissue change compared to the other allergens. Our experience with budesonide showed a tendency similar to that of neomycin sulfate (10), but with Myroxylon Pereirae we detected highest reactivity of reactions with both methods at the same time or first with the visual assessment approach (12). These findings reflect a different time factor between highest perfusion and strongest morphological response to patch tests with different allergens.…”

“…4. We have generally found little or no change of the timing in relation to doses or application times with patch tests of 3 different allergens; nickel sulfate hexahydrate (7), budesonide (10) and Myroxylon Pereirae (12). However, with methylchloroisothiazolinone/ methylisothiazolinone patch tests, we found an unpredictable timing in relation to a change either in application time or of dose (8).…”

“…This study demonstrates that the laser Doppler perfusion imaging technique appears to be a good method for objective and non-invasive assessment of perfusion of neomycin sulfate patch test reactions. In earlier studies, we have even found the technique to be helpful for assessment of patch tests with other allergens; nickel sulfate hexahydrate (7), methylchloroisothiazolinone/methylisothiazolinone (8), budesonide (10,11) and Myroxylon Pereirae (12). In these studies, we have shown that the LDPI may be used to assess inter-individual variation of perfusion of identical patches applied identically and equally long.…”

“…1 and nos. [8][9][10][11][12][13][14][15][16] were read additionally at 240 h (D10), and at 264 h (D11) on all other subjects. During each reading session, all patch test areas not covered by application devices were read ex- cept for a single reading at 72 h (D3) of tests of the strip with the 0.69 and the 0.23 mg/cm 2 neomycin patches.…”

“…The current study uses the imaging technique for perfusion assessments. We have used such imaging before in other studies on patch tests (6)(7)(8)(9)(10)(11)(12). It has also been used by other investigators for patch test assessments (13)(14)(15) and for other applications (16)(17)(18)(19).…”