commercial red wine contains sulfites for preservative reason, 有些人對 sulfites 過敏 , so they have to make their own red wine.
http://www.thekitchn.com/the-truth-about-sulfites-in-wine-myths-of-red-wine-headaches-100878
https://www.wired.com/2015/06/wine-sulfites-fine-heres-remove-anyway/