Use of a combination of two vitamin compounds, i.e. riboflavin (also known as vitamin B.sub.2) and nicotinic acid (also referred to as niacin) or, as an alternative thereto, the corresponding amide, i.e. nicotinamide or niacinamide (also known as vitamin PP) for the systemic treatment of various forms of itching, such as, e.g., pruritus associated with renal insufficiency or failure (i.e. uremic pruritus), and of pruritus forms that are not connected with primary organic affections, as well as for the treatment of a number of non-infective internal affections of a substantially inflammatory nature, such as e.g., urticaria and/or angioedema, asthma, allergic rhinitis and allergic oculorhinitis.