What is Hexylresorcinol? Is it Better Than Hydroquinone for Skin Lightening?

Hexylresorcinol is a chemical compound with anaesthetic, antiseptic, and antihelmintic properties; it is used more as a soothing agent. It is not a chemical lightening agent like hydroquinone is. The serum you are referring to is by Clarins and contains hexylresorcinol, "a lightening active said to be four-times more effective than a 2% hydroquinone." However, the kicker here is that most products contain at least 4% hydroquinone (like Obagi products) and you can even get higher compounded hydroquinone topicals (like 8% or 12%) from a physician. So the two products aren't comparable, and hydroquinone is a much stronger, better skin lightener.