Beyond the ink: Marking the skin with henna through ultrasound gel.

Abstract

Purpose: To evaluate henna as a durable skin marker on various skin tones for sonographic targeting and to identify the shortest duration of henna application needed for practical clinical workflow.

Materials and methods: Prospective study applying seven henna lines through ultrasound (US) gel on the forearms of 15 healthy participants equally represented across the validated six-color bar tool. Color bar categories 1-2, 3-4, and 5-6 were designated low, moderate, and high-melanin groups, respectively. Each subsequent line was applied with staining wait-times ranging from 10 to 480 s. Serial photographs were obtained after scrubbing with chlorhexidine every 2-3 days with the number of clearly visible lines assessed by participants, by individual and consensus physician reads, and by band intensity quantification.

Results: Henna could be applied through US gel and the markings were resistant to chlorhexidine scrubbing. Staining wait-times for 60, 120, and 240 s resulted in visible lines for 6, 8, and 10 days (low-melanin), 5, 6, and 8 days (moderate-melanin), and 2, 3, and 4 days (high-melanin). No lines were visible on day 13 for most participants in the low or moderate-melanin groups and on day 6 on most participants in the high-melanin group. The marking intensities decreased more quickly in the moderate-melanin group compared the low-melanin group.

Conclusion: Henna is an effective skin marker that can be applied through US gel where short staining wait-times result in markings lasting several days. To achieve the same durability, staining wait-times are about double for high-melanin skin tones compared to low or moderate-melanin skin tones.