Ammonium bituminosulfonate or ammonium bituminosulphonate (ichthyol or ichthammol, CAS#8029-68-3 brand names: Albichthyol) is a product of natural origin obtained in the first step by dry distillation of sulfur-rich oil shale. It is used in medicine as a remedy for treating some skin diseases, including eczema and psoriasis. It is commonly used in 10% or 20% concentrate ointment form as a salve. It is sometimes called "black ointment" or "drawing salve". Its dermatological action was promoted by German physician Paul Gerson Unna.[citation needed]