Oral sex is not natural and it is not safe.
From the Time article here It’s True. You Can Get Throat Cancer From Oral Sex:
Human papillomavirus (HPV) is a sexually transmitted disease that can cause genital warts or present itself without symptoms. If left untreated, it can also cause cancers of the cervix, anus, penis, vulva, vagina — and head and neck cancers. “HPV being a cause of head and neck cancer was really only accepted about five years ago,” says Dr. Maura Gillison, a professor at the Ohio State University who studies HPV infections in the head, throat and neck. “Before then, no one really cared about oral HPV infections.”
According to the U.S. Centers for Disease Control and Prevention, about 60% of oropharyngeal cancers — cancers of the throat, tonsils and the base of tongue — are related to HPV. It is estimated that every year in the U.S., more than 2,370 new cases of HPV-related oropharyngeal cancers are diagnosed in women and about 9,356 are diagnosed in men;...