Illustrated by Ly Ngo.
First off, you might be wondering what exactly is in that menstrual blood, anyway. Well, it's a lovely combination of: cervical mucus, bacteria, vaginal fluids, the tissue that covers the inside of the uterus, and blood (duh). That endometrial lining thickens every month in preparation for welcoming a fertilized egg. But, if that little egg doesn't get fertilized, the lining is shed and flows out through the vagina.
Now that you know what the stuff is made of, you may be wondering: Does period sex increase your risk for STDs? Well, the answer is yes — but perhaps not for the reasons you think. Although there is some research suggesting that period sex can increase the risk of HIV transmission and other STDs, it's not just the presence of blood that's a factor; because the cervix is more open than usual when you're on your period, it's more susceptible to infection. And, statistically, women who have sex on their period tend to also have more sexual partners, which is associated with an increased risk for STDs that is in no way caused by the menstrual cycle itself.
However, there's surprisingly little information out there about whether or not menstrual blood is safe to actually consume. Although there are reports running around the Internet about people getting nauseous after eating period blood, it seems that the only reason to worry would be those aforementioned bacteria that are present in the blood — or the fact that it can potentially transmit a virus. Keep in mind, though, that some of those blood bacteria can cause gonorrheal and chlamydial infections, so there's definitely a worry about transmission through oral sex.
So, blood hound or otherwise, always remember: safety first. Once that's covered, though, feel free to get it on — all month long.