I have noticed a brown discoloration on the steering wheel of my Lancer. It's on the areas where I usually put my hands, meaning the wheel itself. There is no such discoloration in the middle where the horn is. Also, there is a similar discoloration on the gear stick knob.

My steering wheel is stock. No leather/leatherette/plastic aftermarket add-ons. Obviously, the discoloration is due to some chemical reaction between my hands perspiration and/or secretions and the steering wheel and gear stick knob.

What can I do to remove the discoloration?

Thanks.