You could use unscented baby wipes to wipe the ear pads clean if they don't come off. Make sure they do not contain any skin conditioner like aloe.
If the ear pads do come off you can clean them in water with a small amount of liquid laundry soap, let them air dry and then put them back on the headset.
A google search yielded this result: http://www.headphonesunder100center.com/how-to-clean-over-ear-headphones-correctly/