Ptisan was a barley soup, consumed as daily bread by the Greeks. Hippocrates chose it to feed his feverish patients, because its use was very widespread in his time. Soon after Hippocrates, wheat superseded barley as the main consumed cereal in Antiquity. But owing to numerous medical polemics this barley soup survived in the food for the sick, until up the seventeenth century, even if barley had become an animal feed since the Hellenistic period. Polemics by Hippocrates, Galen, Ibn Zuhr or Giovanni Manardi generated authoritative and controversial texts that insure the longevity of ptisan.