Cunnilingus is injurious to health!
It would be more proper to state that oral sex, whether done to a woman (cunnilingus) or done to a man (fellatio), can be injurious to health. All acts of sex between unmarried couples carry the risk of transmitting diseases between the partners because it is rare that couples engaged in sex outside of marriage are monogamous.
It doesn't take a Ph.D. to understand why. If a person is willing to break God's law and have sex outside of the bonds of marriage, then why would they be inclined to restrict themselves to just one partner?
Multiple partners drastically increases the probability that a person will be exposes to a sexually transmitted disease. Most of those diseases are transmitting through fluids or skin-to-skin contact, especially the skin involving the genitals because it is far thinner than the rest of the body.
Most people engage in oral sex in an attempt to avoid pregnancy, but they fail to realize that conception is only one possible problem resulting from unmarried sex. Disease is a major problem and oral sex does nothing to hinder the spread of sexual diseases. In speaking of the man willing to commit adultery, Solomon warns, "Wounds and dishonor he will get, and his reproach will not be wiped away" (Proverbs 6:23).
The problem with sexually transmitted diseases is that many of them show little to no symptoms for many years. Thus a person unknowing spreads them and is exposed to them. Eventually the disease manifests itself, but by then it is often too late to prevent the damage caused by the disease. Warning against the woman willing to engage in sex outside of marriage, Solomon again warns, "Remove your way far from her, and do not go near the door of her house, lest you give your honor to others, and your years to the cruel one; lest aliens be filled with your wealth, and your labors go to the house of a foreigner; and you mourn at last, when your flesh and your body are consumed" (Proverbs 5:8-11).