The art of henna (called mehndi or mehendi in Hindi & Urdu languages) has been practiced for over 5000 years in Pakistan, India, Africa and the Middle East. Some documentation dates it to over 9000 years old.  Because henna has natural cooling properties, people of the desert, for centuries, have been using henna to help control their body temperature.  They would make a paste from the crushed dried leaves of the henna plant and soak their palms and soles of the feet in it to get a cooling affect.  The cooling sensation was felt throughout the body for as long as the henna stain remained on their skin.  Initially, as the stain faded away, it left patterns on the skin's surface which led to ideas of making designs for decorative purposes.  In the ancient Egyptian times even mummies wore henna designs and it is documented that Cleopatra herself used henna for decorative purposes