Magic is pure, unadulterated thought-stuffs, pushed out of the wizard's mind into the world of things. This is dangerous, as concepts don't want to interact with things and stuff, they want to be shielded inside sentient minds. They will leap from existence in the real plane to the shelter of any sentient being's brain. But then they will burrow inside your brain like a wild animal during a monsoon, seeking shelter at any cost.
It is never safe to look directly at a spell, the eyes are the window to your soul and to your mind, and the path of least resistance. Magic must be looked at through your peripheral vision or in a mirror, never directly.
Looking directly at a spell is like offering an invitation, handing your neural pathways to the spell like a bundle of fresh candy floss to a child. If you are lucky, the spell is weak and will dissipate. If you aren't, it will root around and get comfortable, leaving you a gibbering mess, repulsed by all magic until the psychic energies finally drain away from inside your skull, leaving you a shade odder and much more neurotic than you were before.
Inspired by Arnold K.'s GLOG wizards and Thuvia, Maid of Mars.