Is it permissible in Islaam to take fish and milk in Islam? Any negative effect on that from the Hadeeth or proved medically?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

In Islam it is permissible, in principle, to eat or drink anything on which no prohibition has been mentioned. As it is permissible to eat two kinds of food or drink two types of drinks, or consume food and have a drink at the same time. Allaah says (interpretation of meaning): {Say (O Muhammad "I find not in that which has been inspired to me anything forbidden to be eaten by one who wishes to eat it, unless it be Maytatah (a dead animal) or blood poured forth (by slaughtering or the like), or the flesh of swine (pork, etc.) for that surely is impure, or impious (unlawful) meat (of an animal) which is slaughtered as a sacrifice for others than Allaah (or has been slaughtered for idols, etc., or on which Allaah's Name has not been mentioned while slaughtering.}[6:145].

No narration has been mentioned regarding forbidding eating fish and drinking milk, so it is permissible. The questioner might have read an expression which is often repeated in language books, which is: "Do not eat fish and drink milk". This is just a linguistic example and has nothing to do with an Islamic prohibition, according to our knowledge.

Allaah knows best.