The UV Erythema Test as a Model to Investigate the Anti-Inflammatory Potency of Topical Preparations – Reevaluation and Optimization of the Method

Abstract

Background: The ultraviolet (UV) erythema test is one of the most frequently used methods to investigate the anti-inflammatory potency of topical dermatological preparations in vivo. Methods: The following questions were addressed in four separate studies with healthy persons (skin types 2 and 3): (1) the optimal localization was determined by comparing light scales on the back, buttocks and volar forearms; (2) the optimal UV-B dose was determined by comparing the 1-fold, 1.5-fold and 2-fold minimal erythema doses (MEDs); (3) hydrocortisone and prednicarbate were evaluated as positive controls, and a sample size calculation was performed, and (4) betamethasone valerate and pimecrolimus were tested as further positive controls in the optimized study model. Results: The back proved to be the best localization for the UV erythema test. It showed a good correlation between the light scale and the test areas. The 1.5-fold MED was the best irradiation dose. In contrast to prednicarbate and betamethasone valerate, hydrocortisone was a rather weak positive control. However, when the sample size was ≧40 subjects, significant results were also obtained with hydrocortisone. Pimecrolimus was not effective in the UV erythema test. Conclusions: The UV erythema test should be performed on the back with at least 40 subjects using the 1.5-fold MED. It may be useful to include a potent corticosteroid, such as prednicarbate or betamethasone valerate, in addition to hydrocortisone. The UV erythema test seems to be suitable only for substances with corticosteroid-like effects, since in this test model the calcineurin inhibitor pimecrolimus was not effective.

Investigation of the Anti-Inflammatory Potential of <i>Aloe vera</i> Gel (97.5%) in the Ultraviolet Erythema Test

“…Obviously, the onset of the effect of botanical ingredients is delayed. This observation was also made in other studies that tested topical herbal preparations [18,19] .…”

“…On this background there is an increasing scientific interest for herbal ingredients as anti-inflammatory agents. For screening purposes in vivo, the UV erythema test is emerging as a suitable tool [18,19,[22][23][24] . Previously, the results of several controlled clinical studies had been in favor of the anti-inflammatory properties of A. vera [6,7,25,26] .…”

“…The UV erythema test was performed as described [19,21] . In brief, for the determination of the MED, gradually increasing doses of UVB were administered on the lower back.…”

“…Twenty-four hours after irradiation, the first barely perceptible erythema with sharp borders was defined as MED. After the erythema index zero value (baseline) had been measured in the test areas with a Mexameter [19] , half of the test areas were irradiated with the 1.5-fold MED of UVB. The other half of the test areas was not irradiated ( fig.…”

“…The most frequently used method in preclinical studies and screenings for active constituents is the UV erythema test [16][17][18] . Recently we have shown that the back is the best localization to perform the test, and the optimal UVB dose is the 1.5-fold minimal erythema dose (MED) [19] . Here, we investigated a concentrated A. vera gel (97.5%) in comparison to 1% hydrocortisone in placebo gel as well as two commercially available corticosteroid preparations, one containing 1% hydrocortisone (Dermallerg-Ratiopharm cream 1%) and the other containing 0.25% prednicarbate (Dermatop cream).…”