Balanced intake, absorption and utilization of macro‐ and micronutrients, including carbohydrates, protein, fat, vitamins and minerals, are necessary for the function of various physiological processes and metabolic reactions. Derangements in this critical balance may lead to disease states with significant cutaneous and systemic manifestations. This chapter provides a comprehensive overview of various essential nutrients and their associated biological significance, as well as the important clinical syndromes that result from their deficiency or excess.