The Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1833-1909), in Parashat Pinchas, mentions a number of types of foods and other substances that one must not ingest, due to the potential risks posed by these items (listen to audio for precise citation):
1) One should not eat an onion or garlic if an entire night had passed since it was peeled. This applies only if it was entirely peeled; if a piece of the peel remained, then one need not be concerned. Furthermore, this danger does not arise if the onion or garlic was mixed with other foods, such as in a salad, or if had been cooked or pickled.
2) One should ensure that no human sweat ever enters his mouth, with the exception of the sweat on one's face. The Ben Ish Chai writes that ingested sweat is "poison" to the body.
3) A person should never place money in his mouth.
4) If a person salivates upon seeing food and experiences a craving to partake of it, he should ensure not to swallow that saliva; he should rather expel it from his mouth so as to avoid the harm it could cause.
5) The Talmud Yerushalmi mentions that partaking of hot bread can cause fever, Heaven forbid, and one must therefore avoid hot bread. The Ben Ish Chai records that the practice in Jerusalem was to avoid even mildly warm bread, but in his view this concern arises only with regard to bread that is exceedingly hot, as suggested by the Yerushalmi's formulation ("Chamimei De'chamimei").
