Google's John Mueller was asked on Twitter Myriam Jessier if it makes sense to use subdomains for the YMYL content on a larger site. She asked "if a subdomain talks about a YMYL topic, can it impact the rest of the site?" John Mueller didn't really give an answer, which surprised me a bit - to be honest.
The full question was "If a subdomain talks about a YMYL topic, can it impact the rest of the site?" The added this additional context, "an online publication with a subdomain per theme - health, horoscopes, gossip news, etc."
John responded saying "We don't have any specific guidance around that from Search, so I'd see it more as a user-experience-themed topic."
We don't have any specific guidance around that from Search, so I'd see it more as a user-experience-themed topic.
— 🐝 johnmu.xml (personal) 🐝 (@JohnMu) May 27, 2022
Back in April 2021, John Mueller of Google actually did advise one case to break YMYL content into its own site from the non YMYL content. He said then "it's always going to be challenging for Google's algorithms to figure out how to deal with that website. So regardless of anything around YMYL or EAT or anything, if you have this mix of very polar opposites almost with regards to content, then I would assume that Google's algorithms are always going to struggle with figuring out how how to rank your website."
So there is no clear guidance from Google on this topic, it does depend a lot on the specific site and situation I guess.
Forum discussion at Twitter.