a.) use a mattress protector. they are waterproof and prevent transfer from body<->mattress. b.) people naturally sweat and have oils in their skin that get t

a.) use a mattress protector. they are waterproof and prevent transfer from body<->mattress. b.) people naturally sweat and have oils in their skin that get transferred through sheets. it's normal to have discoloration where you sleep. that's another reason a mattress protector helps (easier to replace a $50 cover than a $$$ mattress).