I have a pet dwarf rabbit who is 4 1/2 years old. We keep him on the closed in porch with lots of shade and two fans that do not blow directly on him. A couple of days ago I noticed a patch of hair missing behind his neck, when I looked closer at it I saw that there was a scrap looking thing. No blood but it was in the flesh. I figured he just scrastched himself on something. Last night when I noticed another patch of hair on the ground and the sore seemed to be a little bit larger. I know that the shed their hair in the summer but I've never seen it go all the way down into the skin. Is there something that could be causing this medically?