Unexplained Scratches on My Back

Many years ago while living with my parents probably around 1990,
Australia

At this time I was living outside in a garage, yes creepy.
On one night when waking in the morning, everything was fine until I went inside the house, my mum was like what is that blood on your back, I am like what are you talking about mum.
Anyway while stepping into the bathroom, I looked into the mirror at my back, I was like what the hell is that on my back large long red bloody scratch marks, though I didn’t know they were there, to this day I still don’t know how this happened, i never had any finger nails as I always chew them down.

My first tour at a haunted house in Florida USA.
On our first stop at the Spanish War Asylum, creepy place this is, while standing between 2 of the beds, this room was located in the old disused basement, when i came outside into the garden area my friend was screaming at me, saying look at your ankles, they were covered in blood, long gashes and scrapes, I don’t know how this happened because I didn’t feel anything while standing next to the beds, the staff at the Asylum were shocked, but gave me some bandages which my friends helped me apply, the odd thing is the scratches didn’t hurt at all.
I am sure there is some sort of explanation to this, but it`s something I think about each time I visit Florida.
http://www.themurky.com/demons/unexplained-scratches-on-my-back/