Saliva - the key to the Aztec chilli smoke punishment

The great Mexican historian Alfredo López Austin provides the answer in his masterful work The Human Body and Ideology:-
’Saliva was intimately related to the emotional state of anger... As a product of anger, saliva was equated with poison and, metaphorically, with lies. Molina’s Vocabulario gives the meaning of iztlactli as “drivel, but it can also mean lie or poison”... An excess in production of an element of the body caused discomfort or illness. After an individual had suffered an emotional upset, his saliva, charged with ire, had to be discharged. The sources state that among the punishments the Nahuas [Aztecs] inflicted on children or young people was to expose the minor’s face to smoke from burning chile peppers. The sources do not make clear the purpose of such a drastic measure, but Calixta Guiteras thinks the explanation given by contemporary Tzotziles may be the correct one:-

The smoking chilli punishment for an Aztec child - detail from a mural by Regina Raúll, ‘Paisaje Mexica’ (1964), National Museum of Anthropology, Mexico City