That's why I have a screen protector on mine 
I would try a cloth with slightly dampened with water and see if that does the trick.
Maybe you can use/have those clean-your-computer-screen vials
HTH,
Marci

I would try a cloth with slightly dampened with water and see if that does the trick.
Maybe you can use/have those clean-your-computer-screen vials

HTH,
Marci