Daniel_

To establish my credentials, I am Quality Manager for a Sexual Health products company.

The answer is that yes, it is best to use a barrier for any anal play.

The best rule is "Never put anything into an ass and then into anything else"

If you delve deeper, you find that there are already significant levels of bad bacteria in your mouth and nose, so if you lick someone's ass and then their pussy they probably won't get problems - however to be sure you should wash before and after with a personal hygeine product that includes a bacteriostatic ingredient (like Triclosan). That prevents gut bacteria from establishing in the vagina.

Use of dams is a good way of preventing transmission of gut bacteria into the vagina, but they're not especially sexy.

If you and your partner are clean and STI free the risks from unprotected genital/anal sex or oral/anal sex are reduced. Nothing in life is risk free.

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Overhead, the Albatross hangs motionless upon the air,
And deep beneath the rolling waves,
In labyrinths of Coral Caves,
The Echo of a distant time
Comes willowing across the sand;
And everthing is Green and Submarine
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