I have these lines on my back which look like a cat scratched me -- furthermore-- they are all horizontal and about an inch apart from one another. the lines are raised and are not flat, thus, the appearance is of a scar or thin welt on my back.

Dermatographia: Did you lean against something that pressed into your back and caused these welts. You may have dermatographia. Here's a site to read more about that condition. http://www.riversideonline.com/health_reference/Disease-Conditions/DS00755.cfm

LINES ON BACK ITCHY?: IF THESE LINES ARE ITCHY, IT COULD BE A PLANT DERMATITIS, LIKE A POISON IVY RASH. SEE YOUR PCP OR A DERMATOLOGIST.