This paper investigates the practice of early alchemy, by examining how medicine, pharmacology and a broad set of dyeing techniques interacted with each other in the oldest known alchemical treatises. These treatises were written down during the first to second centuries CE, and ascribed to different authors, including the Greek philosopher Democritus, the Persian “magus” Ostanes and the Egyptian “alchemist” Pebichius. I shall draw attention to some theoretical passages in which the most ancient authors explicitly refer to medical practice in order to explain how to treat different base materials with specific dyeing drugs. In particular the notion of pharmakon – both “medicine” and “dyeing drug” – will be analyzed by taking into account specific examples related to some particular ingredients, starting with quicksilver and its role in medical and alchemical writings.