Before Julie came home from Morocco (she stayed on a couple of weeks to host a family member), she had henna applied to her hands. You can see it here moments after she had it done:
It was applied to both the front and back of her hands. It’s lasted at least two weeks. I’ve been interested to observe, however, that the dye on the back of her hand has faded more quickly than that on her palm.
I had initially assumed that the inside of her hand would fade first. After all, that’s the part that interacts with the world. I assumed it would slough off more skin cells. Apparently I was wrong.
I have two possible explanations for the actual fading pattern:
- The palm is more oily than the back of one’s hand. Maybe the oil helps to preserve and protect the design?
- The back of Julie’s hand was exposed to more light, and that’s faded the design more rapidly.
I think this second thesis sounds solid, but I really have no idea. What do you think?
Just a note for potential henna recipients: henna is not black. If you’re anywhere, and somebody wants to apply black-coloured henna to your skin, run in the other direction. It may contain a hair dye that includes para-phenylendiamine, which can cause permanent scarring on the skin.
DarrenBarefoot.com 
I had henna done this past summer and henna stains darker on your palm as the skin on your palm contains more keratin (a particular protein in skin) and the pigment in henna binds to keratin. Perhaps it isn’t that it fader faster on the back of her hand, but rather it started out lighter.
Based on information from a friend of mine, who just had her hands done with henna for an engagement party, henna adheres more to areas of the body with more heat. So, the palms of your hands get a darker design than the much-cooler backs of your hands. (Or so she was told)
No scientific explanations here, but I can concur that the back of my hand (and inside of my wrist) didn’t actually take the pigment at all – only the palm of my hand has the orange pattern.