You may be interested in this thread, wherein:

• I discuss how Moche rulers used analogies of oral sex to reinforce power relations

• /u/sunagainstgold provides us with the finest Catullus poetry

• /u/bigbluepanda and /u/lordtiandao descrbe the practice's history in China

So I think part of the issue that arises with this question is that it's pretty hard to pinpoint "the time before hygiene." Was that ancient history? The Middle Ages? The 1700s? And where? Asia? Europe? Africa? The US? Different time periods and different places all had their own views of cleanliness and hygiene, so it might help if you were to narrow your focus a bit.

But here are some previous posts to check out while you wait for an answer:

• Fabulous thread from just a few days ago that discusses Roman views on body hair that really aren't too different from our own today. /u/Celebreth's comments include not only an artistic depiction of cunnilingus, but some interesting info on how the Romans viewed oral on a man vs on a woman. https://www.reddit.com/r/AskHistorians/comments/a1z5e9/is_removing_pubic_hair_a_modern_fad_or_did_any/

• A nice thread on views on bathing in 15th/16th century Europe: https://www.reddit.com/r/AskHistorians/comments/5tzvng/is_it_true_that_baths_and_personal_hygiene_were/

• Which leads us neatly to Japanese bathing practices, and another discussion about oral sex prior to the modern era. This one has some great answers from various places and time periods: https://www.reddit.com/r/AskHistorians/comments/2cjuxy/how_did_people_tolerate_oral_sex_before_the_age/

• This thread features oral sex in Rome, China, South America, and (gasp) even the Bible: https://www.reddit.com/r/AskHistorians/comments/4lyy9e/was_oral_sex_an_invention_of_modern_western/

• Another thread on oral sex, this one specifically in the Middle Ages: https://www.reddit.com/r/AskHistorians/comments/8hze50/medieval_sex_how_did_the_idea_originate_in_the/

Happy reading!!

Are they "common" now?