I have what may be a spider bite on the back of my head a bit above hairline that has been there for 3 weeks. It is the size of a pencil eraser, raised bump scab-like, red, and irritated. I have been using hydrogen peroxide, 91% isopropyl, & neosporin over the last 3 weeks but still has not healed. Could it be from a spider or a foreign object like a splinter that has encapsulated itself? I have no other sores and good bathing habits.