Can Sharks Smell Period Blood

As a scuba instructor, I’ve had many girls/women ask me if it’s okay to go scuba diving while on their periods. I also get questions from students asking me whether sharks are attracted to period blood. I've also wondered myself, can sharks smell period blood? So in this article we’re going to look at some of the questions surrounding blood and sharks!

Are Sharks Attracted to Periods?

Are Sharks Attracted to Period Blood?

No, and that’s because period blood isn’t really blood at all. It’s a mixture of old uterine lining and cervical mucus that sharks aren’t really keen on. Period blood is kinda like ‘old blood’ that your body is trying to get rid of. Sharks are much keener on fatty, blubber that's alive with fresh blood flowing through. 

Can Sharks Smell Period Blood?

Yes, it’s true that sharks have an amazing sense of smell. But the myth of sharks being able to detect a tiny drop of blood in the ocean from miles away has mostly been exaggerated.

Sharks have nostrils that are located beneath their snouts. How they smell is having the flow of water moving through their nostrils, to the nasal duct and then to the sensory cells. When blood enters water, the chemicals dissolve and this is what can be picked up by a shark. This means that you old menstrual blood would need to flow through the currents and the motion of the water to reach the shark. 

But remember, even if the old menstrual blood cells did make it to the shark, he’s just isn’t into you. Like Dr. Steve Kajiura of Florida Atlantic University’s Shark Lab says, “You can smell a landfill, but it won’t make you want to eat it.”

Is There A Higher Risk for A Menstruating Woman?

No. As a menstruating woman, we can totally relax in the water. On average, we will lose about 3-5 tablespoons of menstrual blood during our periods. That’s nothing compared to the ocean. We can also breathe a little easier knowing that according to the National Geographic, 93 percent of shark attacks between 1580 and 2010 were on males. Sorry dudes! 

Also, remember that most shark attacks were a case of mistaken identity. Surfers and people swimming usually look like the silhouette of a sea lion or seal. When we splash around on a surfboard, we especially look like an injured sea mammal, which is much more appealing to sharks with their fatty blubber. Humans are generally very bony and not fatty enough for sharks, and when sharks do accidentally attack a human, it’s because they are curious and trying to figure out what we are!

Can you go Swimming on your Period?

Yes, you can. Check out our other article for an in-depth read on whether you can go swimming on your period, and what products are best for this awesome activity!

Can you go Scuba Diving on your Period?

Totally! I do it every month! Personally I find the menstrual cup to be the most comfortable, and easy to empty and reinsert on a dive boat. There’s no issue with menstrual cups and the increasing pressure as you dive deeper. I’ll write up an article about scuba diving and menstrual cups soon. Watch this space!

The Takeaway!

So there you have it. Sharks might be able to detect a bit of menstrual blood if you were super close, and your gushing blood happened to be flowing in their direction over their nostril holes! But even if they did smell you, they wouldn't want your old, cervical mucus when a great big fatty sea lion is on the menu. So get out there, and go for a dip in the ocean, and don't fear this ancient, majestic apex predator who helps keep our ecosystems in check!

Can sharks smell period blood - yes, but they are not interested!

Laura Otto - February 12, 2020
For starters, the notion that a shark can smell blood “from a mile way” is not true. Plus, though sharks can detect blood from a quarter of a mile away, period blood is not blood. Not just blood, anyway. menstrual fluid contains “cervical mucus, vaginal secretions, mucus and cells and endometrial particles as well as blood (sometimes clotted).” If it were true that your period could attract sharks, a shark would need to be able to sniff out blood that was mixed (or possibly masked) by non-aquatic mucus and have to be able to sense endometrial particles.

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