Dental dams are easy to use. Before using the dam you may want to rinse off any powder that's on the dam and check to make sure there are no holes or perforations. The partner performing oral sex will hold the dam against the vulva or anus of the receiving partner. You can opt to apply a lubricant on the vulva or anus before using the dam. The lubricant can help increase the sensation for the recipient. Be sure to use a water-based lubricant, because oil-based lubricants and lotions will degrade the latex and decrease the dam's effectiveness.
Some important points to keep in mind:
When you use the dam, be sure to ONLY use one side. If you turn the dam over and continue to use it, you will expose yourself to the very fluids you're trying to avoid.
Do not re-use a dam on another body part (e.g. from anus to vulva or vice-versa) because you can transfer germs from one body area to another.
Dams are for one-time use only.
Many people believe that using a dam will reduce the enjoyment of oral sex. The feeling of latex will be different than a tongue, but using a dental dam with lube can offer a new and pleasurable type of stimulation.
Although oral sex is considered less risky than vaginal or anal sex, there is still a risk of transmitting STIs. To be as safe as possible, use a dental dam for every act of oral sex.