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Can Sharks Smell Period Blood? Why They Won't Attack

Your friends want to plan a weekend at the beach, but it falls right on the heaviest days of your period. Do you have to cancel plans? The short answer is no. But if you’ve got questions about marine life and your period, you’re not the first to ask. 

We aren’t sure where the rumor started, but it seems like a time-honored belief that swimming in the ocean while on your period can attract sharks. If you’re afraid of booking that beach bungalow because of your monthly cycle, we’re here to give you peace of mind. 

Let’s “dive” into a discussion about your period, shark attacks, and whether or not swimming on your period will make you a shark snack. 

Facts About Your Period

Some of the confusion around shark attacks and periods comes from a misunderstanding of how your period works. Even if you’ve had your period for a long time, you still might not know some of the basics. Let’s look at a few facts you should know. 

1. Your Period Isn’t Just Blood

Many of us wrongly believe that our period flow is just blood, but that isn’t the case. Your monthly period is made up of three main fluids: blood, vaginal fluid, and cells shed from the lining of your uterus. Only about half of your period flow is blood. 

2. Your Period Is a Lot Less Than You Think

Sometimes it seems like your period flow is more like a waterfall than a constant trickle, but in reality, your period flow is a lot less than you think. 

On average, you’ll lose about three tablespoons of menstrual fluid every period. Even a heavy period will usually only produce about four tablespoons. It may seem like you’re floating down a red river, but that just isn’t the case. 

If, however, you know your period is heavier than three to four tablespoons of flow each month, it’s a good idea to talk to your doctor. Sometimes, a heavy period is just normal for your body. It could be an indication of something else, or there might be a way to have lighter periods. 

It’s Perfectly Safe To Swim on Your Period

Over the decades there have been some crazy ideas about what’s dangerous on your period. In fact, in the 50’s and 60’s, women didn’t wash their hair while on their periods. Thankfully, today we know that it’s safe to wash your hair (and every other part of your body) when you’re on your period. 

It’s also safe to swim while on your period, if you use proper protection. There’s no safety risk to you if you decide to swim on your period, just like there’s no risk if you wash your hair on your period. 

Facts About Sharks

We aren’t marine biologists, but we contacted the experts to find out some basic facts about sharks and how they react to blood (especially the kind you have on your period). 

1. Sharks Can Detect Blood Very Easily

Sharks have larger olfactory glands than humans, and can detect even small amounts of blood from far away. In fact, great white sharks can detect a single drop of blood within a three mile radius. 

The point is that if there is blood in the water, a shark can sense it. Even if you have a small cut on your finger or a jagged cuticle, the blood is detectable by a shark. However, it’s important to keep in mind that you aren’t the only life form swimming in the water. 

When you are swimming in the ocean you are surrounded by scores of fish and other marine animals, which are also detectable by a nearby shark. 

2. Sharks Can Detect Other Bodily Fluid

Sharks don’t just detect blood, they can detect other bodily fluids, like urine. They can also detect secretions made by fish and marine plants. Just because a shark can sense these secretions does not mean the shark recognizes it as a food source. 

Sharks don’t consider humans part of their diets. They’d much rather prey on fish and other ocean life than attempt to attack a human. 

Shark Attacks Are Rare

Your chances of being attacked by a shark are pretty slim. In fact, the average yearly shark attack rate worldwide is around 80. Sharks just aren’t interested in attacking people. They’d much rather consider more vulnerable prey. 

When sharks do attack people, it is typically because they are confused or feel threatened. This can happen because they mistake a raft or surfboard for something else, or because you are swimming in an area that is known to have a high presence of sharks. 

Facts About Swimming in the Ocean on Your Period

Swimming in the ocean while on your period does not increase your risk of being attacked by a shark. There’s just no evidence to prove that a shark is attracted to period blood, or that you’ll somehow bleed so much while in the water that a shark would be prompted to attack you. 

Here are some other interesting facts about swimming in the ocean while on your period. 

1. Your Period Flow in the Ocean

When you swim on your period, you may think your period suddenly stops, but it hasn’t. The water pressure you experience when you swim can keep your period blood trapped inside until you stop swimming, but it doesn’t magically cause your period to actually stop. 

2. Period Blood Dissipates in Water

Any blood that may be released while you are in the water quickly dissipates into the surrounding water. This means the blood moves away from your body and moves along with the water in the ocean. 

In other words, if blood escapes your swimsuit, it isn’t going to hang around your body attracting sharks. 

3. A Tampon Offers Great Protection While Swimming

Tampons offer great protection while you swim. Tampons make it possible for you to swim, exercise, and participate in virtually any activity while you’re on your period without worrying about leaks. 

Rael’s organic cotton tampons are free from harsh chemicals that could make you sick or interfere with your hormones, and offer the protection you need to surf or swim no matter what time of the month it is. 

The best part, wearing a tampon means you don’t need to worry about bleeding while you’re in the water. The tampon will absorb your flow while you swim, so you can forget about your period (and sharks). 

As a side note, remember you’ll need to change your tampon every four to six hours. You may have to change your tampon sooner while swimming; there’s a possibility it can absorb a little water, especially if you’re engaging in vigorous activity like surfing or water-skiing. 

How To Swim Safely While on Your Period

Even though swimming on your period is safe, there are guidelines you should follow to make sure you’re safe. 

  • Use a tampon or a cup. When you’re swimming on your period, it is possible to swim without period protection, but you’ll risk an embarrassing situation when you exit the water. 

    The best way to make sure you’re protected while you swim is to wear a tampon or use a menstrual cup. A menstrual cup is a flexible, silicone cup that is placed securely inside the vagina to catch your flow. 

    You can wear a menstrual cup for up to 12 hours, which makes it ideal if you plan to take a boat ride to a sandbar during low tide, or spend the morning catching waves. 
  • Swim near a lifeguard. When you swim in the ocean there are numerous dangers (other than sharks). To make sure you’re safe, always swim where a lifeguard is on duty. A lifeguard does more than rescue you if you’re in trouble; they also keep an eye open for marine life activity so they can warn swimmers of any nearby threats. 
  • Swim with a buddy. It’s never a good idea to swim by yourself. Between riptides, ocean creatures, and large waves, having a friend to swim ensures if something happens, you’ve got back up.

Play it safe when you swim and you can have a great time in the water, even if you’re on your period. 

The Takeaway

Go ahead and book that beach vacation, and let Aunt Flo come along with you. Sharks may be able to detect blood, but being on your period won’t cause a shark to attack. You can swim in the ocean on your period without worrying about sharks or leaks by wearing a tampon or a menstrual cup. 

Rael offers holistic, effective period care products to keep you comfortable all month long, whether you're on the sand or in the sea. 


Proteomic Analysis of Menstrual Blood | NCBI 

Heavy Periods: Overview | NCBI Bookshelf 

11 Facts About Sharks | 

Do Sharks Hunt People? | 

Yearly Worldwide Shark Attack Summary | International Shark Attack File

Menstruation and Sharks | International Shark Attack File  

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