Henna tattoos are wearable art. The paste, made of crushed leaves and twigs, is applied to your skin in intricate designs to stain the outer layer of your cells. As your skin naturally sloughs, so does the tattoo, which will generally last seven to 14 days. (Some darker tattoos can last as long as three weeks.) People lose skin layers at different rates, so there's no guarantee as to how long you can keep it fresh. But a little care can help you extend the life of your henna tattoo.

If you are doing your own tattoo, leave the dye on your skin for the longest possible time for the deepest, most saturated color. Warmth makes the dye more potent, so gently heating the paste before it's applied or choosing the warmest parts of your body, such as your palms, for tattoos is recommended.

Some tattoo artists suggest leaving the henna dye on overnight before rinsing or flaking off the paste. Henna paste dries rather quickly -- in just five or 10 minutes -- so you can leave it on and even sleep in your own bed as the dried paste flakes off. It will not stain your sheets. You can then scrape or lightly rinse off the remaining paste in the morning to reveal your design.

If you're in a time crunch, henna will color your skin in as little as four hours, though the results will be on the lighter side. They will also slough off much more quickly than dark tattoos.

If you're mixing henna yourself, thin the powder with lemon juice. The acid in the juice helps release the pigment and give it greater staying power. Add a little granulated sugar to the henna mixture, too, in ratio of 1 part sugar to about 5 parts henna paste. The sugar keeps the paste from drying as quickly when applied, so the dye saturates your skin for longer. This helps the tattoo develop a deeper, longer-lasting color. It also optimizes the henna's texture for application.

Once you're tattooed, wrap the area with plastic wrap -- carefully so you don't smudge the design -- and then in warm towels. The heat keeps the dye seeping into your skin a little longer, resulting in a darker color that may last longer.

Of course follow personal hygiene, but the less often you wash the area to which the henna has been applied, the longer the tattoo will last. Avoid using exfoliators and rough scrubs, which take off the layers of skin that hold the henna coloring.

Before getting a henna tattoo, you may also want to avoid shaving and exfoliating; these leave your skin without enough layers to fully absorb the stain. Avoid any body work -- even massage or waxing -- a day or two before the tattoo.

Water contact, even without exfoliation, degrades your henna tattoo. So, for at least 24 hours after getting the tattoo, avoid household chores that require getting your hands wet, and stay away from chlorinated pool water.