I have been surprised over the number of posts regarding dildos and large dildos for anal use during the last few months. Previously, I posted quite completely on anal sex and its possible consequences. Those posts were generally for women but the number of men seeking dildo action in their rears has increased.
The anus, whether male or female, is designed as a one way valve; it lets stuff out but resists letting anything in. The tissue of the anus and the rectum is one cell thick, whilst the vagina is forty cells thick. The vagina, designed to admit penis (or other objects) is very elastic and can handle about anything. The muscles at the opening of the vagina are also designed to stretch to allow birth. Tears in the rectum and anus are quite common as people begin taking this action. These tears, of course, admit bacteria that cause infection and the stuff travelling through rectum is about as full of bacteria as you can imagine. The anal sphincters are not and can easily be stretched, even torn, to the point that they do not do their job.
In the long term (several years) the cumulative effect of anal sex, especially with very large dildos, can be expected to be hemorrhoids, possible loss of bowel control and infections.
Yes, I know some will engage in anal sex and even come to enjoy it (Confession: I thoroughly enjoy anal play but do not allow penetration) but certain precautions should be taken: Always use a condom when a real penis is involved. This works both ways. The worst prostatitis I have ever treated was from fecal material jammed up the penis in someone's anus. If using a toy, it should be thoroughly cleaned and have a vinegar soak each time it is used - or cover it with a condom. Second, LOTS of lube on both the receiving anus and on the object penetrating. Old fashioned, water-based lubes such as K-Y and Surgilube do the job, clean up easily and will not cause allergic reaction in anyone. Any colored, flavored, warming, numbing or other tricky should be avoided. The additional chemicals increase the risk of damage and allergic reaction.
You would not believe the things removed from there in the typical emergency room on any weekend night. Sure, we can get it out but it should not have been there in the first place.