Sakanah
Personally, I don't follow this one.... Orthodox Jews avoid eating fish and meat together because the rabbis treated the combination as a matter of sakanah , danger, not as the same category as basar b’chalav , meat and milk. The root source is the Gemara, Pesachim 76b , where fish cooked or roasted with meat is discussed as dangerous. The concern given there is rei’ach and davar acher , which Rashi explains as a danger connected to tzara’at , a skin affliction. This is later codified in halakhah. Shulchan Aruch, Yoreh De’ah 116:2 says: One must be careful not to eat meat and fish together, because it is dangerous. The Shulchan Aruch, Orach Chaim 173:2 also treats separation between fish and meat as required because of danger. That is why many Orthodox Jews will eat fish first, then cleanse the palate before meat, often by eating or drinking something in between. Unlike meat and dairy, there is usually n...