Pretty much like henna, cassia obovata leaves contain a substance that acts as a translucent, slightly yellow gloss on the hair. We can compare it to the effect of varnish on a piece of wood: by entirely coating each strand of hair the plant makes them look lustrous and smooth. The only difference with henna is that it has almost no colour.
A little leguminous plant with oval leaves and yellow flowers, cassia obovata mainly grows in the Middle East, India and above the equator in Africa. The plant actually changed names for Senna italica some times ago, making ‘Cassia obovata’ and ‘Cassia italica’ what botanists call ‘a homotypic synonym’. This means that we can still call them by any of these names, but one is a bit more official. A classic botanical imbroglio!