Filaggrin proteins are important for the epidermal differentiation and skin barrier function. About 10% of Europeans carry loss-of-function mutations within the filaggrin gene complex. Mutations are strongly associated with ichthyosis vulgaris and atopic dermatitis as well as dry and fissured skin. No overall association with psoriasis vulgaris has been identified. The filaggrin gene discovery has been a major breakthrough for dermatology in terms of diagnostics and prognostics, but it has not yet been translated into therapeutic advances.