It’s 2008. I’m ten years old. I have a henna cone in my hand and I’m not afraid to use it. I squeeze unrecognisable flowers onto the women, and I paint wonky footballs and messy rockets onto the boys.

With a history spanning millennia across the Middle East, North Africa, and South Asia, henna is steeped in tradition and cultural rituals. The natural dye is typically used to create temporary, ...