Gemara

(Rabah and Rav Yosef): We are not concerned for Giluy (exposure) of mixed wine.

(R. Yakov bar Idi): We are not concerned for Giluy of cooked wine.

Cases occurred, and R. Chiya permitted mixed wine that was exposed, and Rav Ada bar Ahavah permitted cooked wine that was exposed.

(Rav Ashi): Exposed wine is dangerous (even if it is mixed.)

Rava: The Halachah is, we are concerned for Giluy of mixed wine, but not of cooked wine.

30b: We are not concerned for exposure of cress only in Bavel, i.e. if it has no vinegar. If it has vinegar, this deters snakes.

31b (Rav Nachman): Beer of Nochrim is forbidden because they leave it exposed (perhaps there is venom inside).

Question: Also we leave it exposed while it is fermenting in the vat, and while it is in the barrel!

Answer: They expose the water used for beer to become clear.

(Rav): If (wine or beer) was exposed, and it was aged, it is permitted. If it contained venom, it would not age properly. If grape juice was exposed, and it fermented, it is permitted. If it contained venom, it would not ferment.

We decree against old beer due to new beer.

(Rav): Beer of Nochrim is permitted. The bitterness of the hops burns the venom. However, a sick person may not drink it, for it will worsen his illness.

(Shmuel): All Sheratzim (rodents) have venom. Snake venom kills, but venom of other Sheratzim does not kill.

(Shmuel citing Rav): Bodies of Nochrim are hot from eating vermin, so this is Mevatel the venom. This is why they do not die due to Giluy.

Chulin 10a (Mishnah): Three liquids are forbidden if they were exposed: water, wine and milk. This is if they are exposed for the amount of time it takes for a snake to come from a nearby hiding place, drink, and return.

(R. Yitzchak brei d'Rav Yehudah): Under the handle of the flask is a nearby place.

49b (Rava): Exposed honey is permitted. A Mishnah forbids only wine, water and milk. Further, the Torah is concerned for the money of Yisrael!

Objection (Rav Nachman bar Yitzchak): The Torah's concern for the money of Yisrael does not override mortal danger and R. Shimon's opinion!

(Beraisa): The following liquids are not forbidden through exposure: brine, vinegar, fish oil, and honey.

R. Shimon: They are forbidden. I saw a snake drinking brine.

Chachamim: Normal snakes do not drink these.

Rava: At least admit to me that brine is permitted. Rav Papa and other Chachamim would put exposed liquids into brine to permit them!

Rav Nachman bar Yitzchak: Admit to me that honey is forbidden, for a Beraisa teaches that also R. Shimon ben Elazar forbids this.

Bava Kama 115b (Beraisa): Exposed wine may not be poured in the public domain, use d to knead mud, sprinkled on the floor, or fed to an animal.

A Beraisa permits declaring exposed Ma'aser wine to be Terumas Ma'aser. This is like R. Nechemyah, who holds that straining it permits it.

Rishonim

Rif and Rosh (Avodah Zarah 10b and 2:13): The Gemara in Chulin 49b connotes that Giluy applies to honey and brine.

Rambam (Hilchos Rotze'ach 11:7): Giluy forbids the following liquids: water, wine, even if it is mixed and even if the taste stared to change to vinegar, milk, honey, and brine. We are not concerned for Giluy of other liquids, for venomous creatures do not drink from them.

Rambam (8): We are not concerned for cooked wine, wine three days from when the grapes were pressed, wine, water or milk so hot that smoke rises from them, or if it was dripping drop after drop. Vermin do not drink these.

Rambam (11): We forbid liquids due to Giluy if they were exposed during the day or at night, even if someone was sleeping next to them. We forbid if it was unguarded long enough for a vermin to come from under the handle, drink, and return.

Poskim

Shulchan Aruch (YD 116:1): Chachamim forbade liquids that were exposed, lest a snake drank from them and put in venom.

Beis Yosef (YD 116 DH v'Elu): The Gemara connotes that brine is not a problem. Rav Papa and Rav Huna brei d'Rav Yehoshua acted upon this! Rava said to Rav Nachman 'you should admit to me that brine is permitted', and Rav Nachman did not answer. This shows that he admitted. The Rashba and Tur do not list brine amidst problematic liquids, but the Rif, Rambam and Rosh do! Since they are stringent about a danger, and rule like R. Shimon, they should also be stringent about fish oil and vinegar! We cannot say that fish oil is brine, for the Beraisa lists them separately! We could say that vinegar refers to spoiled wine, but the other difficulties remain. It seems that since R. Shimon saw a snake drinking brine, we are stringent about mortal danger, even though Chachamim say that it was deranged.

Rebuttal (Bach): R. Shimon said that he saw a snake drink brine just to refute Chachamim who said that they do not drink it. We should be stringent about mortal danger! Nevertheless, we learn from Rav Papa and Rav Huna, who relied on brine to detoxify the poison! The Beis Yosef said that Rav Nachman did not reply about brine, this shows that he admitted that it is permitted. How did he understand the Gemara?! What kind of answer did Rava and Rav Nachman give to each other, 'admit to me that brine is permitted', 'admit to me that honey is forbidden'? Rather, Rava said 'admit to me that the Halachah does not follow R. Shimon regarding brine, and if so, also regarding honey (both are permitted). Rav Nachman said 'admit to me that the Halachah follows R. Shimon regarding honey, and if so, also regarding brine.' Rashi explains like this. The Rif and Rosh rule like Rav Nachman against Rava, Rav Huna and Rav Papa. They learn from Avodah Zarah 30b to permit vinegar. Rava and Chachamim of Neharde'a argue only about wine that spoiled, but not about proper vinegar. They did not need to teach about fish oil, for always it has the same law as brine.

Shulchan Aruch (ibid.): Nowadays snakes are not common among us, so they are permitted.

Gra (1): This is not considered something forbidden through a Minyan (an assembly of Chachamim, which can be permitted only amidst a greater Minyan), for from the beginning it was forbidden only where there is concern for Giluy. E.g. cooked wine and many similar things were never forbidden.

Taz (115:10): Semak says that according to R. Tam, who forbids cheese of Nochrim due to Giluy (of milk), it is forbidden even nowadays. Even though nowadays water is permitted, this is because there was no other reason to forbid it. Everyone knows that it is forbidden where there is concern for Giluy. The Gemara mentioned other reasons to forbid cheese. If we would permit it where there is no concern for Giluy, perhaps people will permit it even where there is concern for Giluy, for they will think that it was forbidden for different reasons (and permit it when those reasons do not apply).

Pischei Teshuvah (1): The SHLaH says that in any case, one who guards his soul will distance from this.

Bach (DH Yesh): The Tur wrote all the laws because snakes are still common in some places.

Mateh Yehonason: Whenever Chachamim forbade unconditionally, e.g. Melachah after midday on Erev Pesach or eating shortly before Minchah (according to the opinion that this is due to Korban Pesach), we cannot permit without another Minyan. Milk of Nochrim was forbidden lest they mix in Tamei (pig's) milk. It was never forbidden if a Yisrael supervises. Therefore, where there are no pigs, it is as if a Yisrael supervises. Likewise, where snakes and scorpions are not common, it is as if we watched and saw that no snake drank!

Shmiras ha'Guf veha'Nefesh (Siman 44, He'aros): The Chazon Ish said that we need not be concerned lest workers (who put milk in bottles or bags) left it exposed.