I have recently thought about buying those rings you place around the penis. They are supposed to enhance the hardness of your erection and your staying power. Are they dangerous? Can they harm you with the restriction of blood flow after you have an erection?
What you are referring to are usually known as cock rings. These bands, when placed at the base of the erect penis, help prevent blood from draining away from the penis, thus promoting firmer erections. Although they do not help men get an erection, they can allow him to keep one if he has difficulty maintaining one. Some men also find that the feeling of extra "fullness" causes more sensitivity and enhances their pleasure. They are not, however, generally helpful in delaying ejaculation and, once a man has an orgasm, he will still have a refractory period and lose his erection.
Erection rings are not generally considered dangerous or harmful as long as they are used correctly and safely. Most importantly, they should not be kept in place for more than half an hour. When a man is erect, there are tubes (known as corpus cavernosa) that are engorged with blood. But, this blood does not carry oxygen to the tissues of the penis. Having an unwavering erection can actually cut off blood supply to the penis. If left on for too long, you can even burst blood vessels, causing bruising, swelling, and sometimes even vascular damage.
For these reasons, I often recommend that if you wish to experiment, use a ring made of fabric or rubber -- something that can be cut in an emergency -- and not metal. And, for God's sake, don't make it so tight that you are ready to burst!
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