The Bleaching is a result of the gnomes' exodus from their home plane. It only serves to fuel their racial curiosity and whimsy. In essence the Bleaching is a sort of unnatural aging that gnomes have experienced since their migration to Golarion. While gnomes are still immortal, they now require regular wondrous or vivid experiences to sustain themselves otherwise they begin to fade, their entire body losing all its colour. The condition is eventually fatal. 
Despite generations of visionary gnomish research, the exact nature of the dire affliction known as the Bleaching remains a mystery. The race’s scholars believe it is tied to the events of the exodus and insist that the mortal world lacks the animus to nourish a gnome’s sophisticated spirit. 
The Bleaching manifests itself as a blanching of skin, hair, and eye color during early adulthood. From there on, the complexion of the gnomish body is tied to the experiences she alights upon. The more shocking and vivid a gnome’s life, the more vivid she herself becomes and the longer she lives. In contrast, a lack of excitement causes a fading of color and is accompanied by depression and the dulling of curiosity, heralding the beginning of a vicious spiral that leads to insanity and death. Due to the effects of the Bleaching, a gnome’s age is not tied to the passing of time. Instead, every year a gnome lives without experiencing new wonders takes a toll on her physiology, causing her to age noticeably.
While many gnomes succumb to the horrific effects of the Bleaching in a long and drawn out process after they cease to excite their senses, some are able to exist in its emotional void. Often fueled by a dramatic trauma, these individuals, called “bleachlings,” remain in a distorted state of consciousness, immune to the final touches of the affliction. Their skin, hair, and eyes seem either colorless or in moderate earthly tones, and their demeanors are calm and dreamy. A bleachling’s connection to the First World is incredibly strong, granting her elderly wisdom and renewed powers of her fey heritage as well as an ageless existence. Bleachlings are generally at least middle age before the aging effects of the process cease to affect them. At this point a bleachling effectively ceases to age.