There are a few concerns with anal sex that people should be aware of. The anus and rectum do not produce any natural lubrication of their own. In fact, they can be quite absorbant, so what ever lubricant you use (your own vaginal lubrication, saliva, or store bought lube) can dry up quickly. That is why that additonal water based lubricant is highly suggested. When a water based lube dries out you just have to either add more or add few drops of water to make it slick again.

It also importnat to use a condom. It is extremely easy to damage the tissue lining the rectum. You can tear yourself which can leave you at high risk for STD's and infections. I also think it is a good way to keep the natural bacteria of your rectum and anus from coming into contact with the penis.

After having anal sex it is very important to put a fresh condom on before entering the vagina. Again, you don't want the bacteria to travel to the vagina. Painful infections can result. Same thing goes for your hands. You need to wash them thoroughly before moving from the anus to another area or wear thin latex gloves (like the one's surgeons wear) and change them if you move from one area to another.