I've just stumbled upon this very interesting artist, Ariana Page Russell. She has a skin condition called dermatographia, where her skin is hypersensitive to the smallest of scratches, causing painless welts that last around 30 mins. Arianna uses this to her advantage and creates beautiful artwork on her body, then photographing it. She's even created some beautifully patterned wallpapers using pictures of her skin. In the first two pictures I think she has used temporary tattoos to achieve this effect. The third picture is caused by etching words onto her skin.
Her newest exhibition "Blouse" starts October 21st 2011 at the Magnan Metz gallery in NY and goes on until 19th November.