Is it Permissible to Eat Fish and Cheese Together?

Greetings,
 
The Sephardic custom is to refrain from eating fish with milk, while the Ashkenazi custom is to be lenient in this regard. Those who have the practice in their family to avoid this should continue with their custom.

Sources: The Sephardic custom to avoid eating fish with milk is based on the writings of the Beit Yosef in Yoreh De'ah (Siman 75), who states that one should not eat fish with milk due to a health concern. For a more in-depth discussion, see the responsa of Yechave Da'at, Part 6 (Siman 48), where it is concluded halachically that Sephardim should refrain from eating fish with milk or cheese due to safety concerns. However, those who are accustomed to eating fish with butter may continue with their practice. See also the responsa of Yabia Omer, Part 10 (pages 334-335), and the responsa of Shemesh U'Magen, Part 4 (Yoreh De'ah Siman 12), and the responsa of Dvar Eliyahu, Part 9 (Siman 50), and the responsa of Berakhat Yehudah, Part 2 (Yoreh De'ah Siman 5), and the responsa of Ya'alat Chen, Part 1 (Yoreh De'ah Siman 2).

The Ashkenazi custom is indeed to be lenient regarding the consumption of fish with milk. See the Rema in Darkei Moshe (there, paragraph 4) who cites the Beit Yosef's statement and writes, "I have never seen anyone cautious about this." The Shakh (paragraph 6) also notes that we have not heard or seen anyone refrain from eating fish with milk, and it is common practice to cook and eat fish with milk regularly. This is also the view of the Taz (paragraph 7) and the Magen Avraham (beginning of Siman 192) who permit eating fish with milk. The aforementioned Yechave Da'at also mentions that Ashkenazim practice leniency in this matter and have reliable authorities upon which to rely.

However, there are some among the Ashkenazim who have the custom in their families to refrain from eating fish with milk, and they should continue to follow their custom. See in the book Hilchot Shlomo on the holidays (Nisan-Av, Chapter 12, note 48) and in the responsa of Even Pella, Part 1 (Siman 121). And see also in the book Sha'arei Halacha u'Minhag, Part on Additions and Supplements (Siman 98) regarding the Chabad custom in this matter.

Blessings,
Hillel Meirs