Wine Touched by Non-Jews

Wine which is not mevushal, boiled, and touched by a non-Jew, or by a Jew who desecrates the Shabbos publicly, is forbidden to be drunk by a Jew, and in many cases forbidden to derive benefit from as well. If the bottle of wine was touched when it was closed, even if it was not sealed, the wine is permissible. However, the bottle must be sealed with a chosam b’toch chosam, a double seal, if left alone in the presence of non-Jew. If a non-Jew touched an open vessel with wine in it, but did not shake it, the wine is permissible as long as there was a Jew watching to make sure that the non-Jew did not shake the wine. Nevertheless, some people are particular not to drink that wine as a midas chasidus, pious behavior. Another stringency, not a halachic issue but a kabbalistic one: some people are meticulous about a non-Jew not seeing their wine, in addition to not touching it. This is something which is not mentioned in traditional halachic sources. Many individuals have adopted this stringency and keep their wine bottles covered with a paper bag so that it should not be seen by a non-Jew. The common custom is to limit this practice to wine used for Kiddush, Havdalah, Zimun, and other mitzvos.

https://halacha2go.com?number=194

Practical Halacha: One minute a day. By Horav Yosef Yeshaya Braun, shlita, Mara D'asra and member of the Badatz of Crown Heights.