Site variation in anthralin inflammation on forearm skin

The effect of application site on anthralin inflammation was measured at 10 clinically normal volar skin sites on each forearm of 31 subjects as the increase in skin thickness at 48 h using Harpenden calipers. Pre-treatment and increase in skin thickness were significantly related to application site. Pre-treatment thickness increased distally and laterally by an amount depending on sex, and to a lesser extent other factors, whilst the increase in skin thickness values was greater proximally, laterally and on the right arm but was not affected by age, sex or skin type. When increases in skin thickness values were adjusted for pre-treatment thickness, the difference between proximal and distal sites was lost but there was still a significant difference between the medial and lateral aspect and the right and left arms. The absolute differences were small but demonstrate the need to use symmetrical forearm skin sites and randomized treatment sides when comparing the effects of topical agents on anthralin inflammation.