Changes to sculpt appear on both sides of the mesh? I'm completely new to 3D sculpting. For some reason when I started working on the eyes of my sculpt it started affecting the back of the head. I thought that it might be a result mirroring, but no matter what I do I'm unable to smooth out the ridges that appeared on the back of the head. If it was related to mirroring I don't think this would happen.
First check in toolbar (T) panel if you have turned on mirroring. It's under symmetry. Glitches during mirroring occur when object is rotated or has non-uniform scale which comes from scaling in object mode. Ctrl - A apply scale to fix that if this is the problem.