The First-Ever Nail & Cuticle Serum – A Nail Care Revolution Since 2005 Onsen Secret pioneered the first-ever Nail & Cuticle Serum over 20 years ago, setting a new standard for deep cuticle repair and nail rejuvenation. Unlike traditional cuticle oils, balms, or creams, our ...The First-Ever Nail & Cuticle Serum – A Nail Care Revolution Since 2005 Onsen Secret pioneered the first-ever Nail & Cuticle Serum over 20 years ago, setting a new standard for deep cuticle repair and nail rejuvenation. Unlike traditional cuticle oils, balms, or creams, our breakthrough formula combines the benefits of a serum, oil, and butter into one fast-absorbing, long-lasting treatment.