Ariana Page Russell has dermatographia, which the Mayo Clinic defines as:
Dermatographia is a condition also known as skin writing. When people who have dermatographia lightly scratch their skin, the scratches redden into a raised wheal similar to hives. These marks usually disappear within 30 minutes.
Ms. Russell is an artist. Where other people might see a disability, she saw an opportunity. She inscribes images, words and patterns on her skin. You can see more photos of her work at the link.