Eucalyptus oil or Mehndi oil is used in the henna paste.
To enhance henna tattoo after it is applied, use the typical lemon juice/sugar paste with a drop of eucalyptus oil dabbed on gently while it is drying so it actually stays wet over a three hour period – it will dye the skin better.
Most scrape off the paste lightly and then leave it dry. The skin around it, if sticky, can be wiped off with a damp paper towel.
Some use vegetable oil to clean around it.