Thisall-purpose cleaner can be safely used in full strength on porcelain, stainless steel and the hard plastics used for toilet seats... so generally, great for bathroom / kitchen sinks, tubs, toilets and appliances. Where it gets tricky is on countertops and floors. Any surface that is porous is a no-go - such as hardwood floor. The lemon in the product will strip the finish and absorb into the wood leaving that opaque white mark that you see if you cut a lemon in half and place it down on a wood surface. Even the coating on stone, marble or quartz might be porous. In these instances, our recommendation is to pump a couple of sprays while you are filling a bowl, sink or pail of hot water (it will foam up a bit) and do a spot test on a discreet location of the surface in question.