Could ancient Aztecs have held the secret to fending off shark attacks?

Can chilies repel sharks?

Some people have proposed using that hotter than hot capsaicin extract for use against sharks. The idea behind one Capsicum shark repellent patent is essentially a pepper spray for sharks. Delivering a shot of Capsicum juice at a shark would irritate the fish's gill membranes and nerves across its entire body [source: Matos and Romero]. Similar types of repellents have worked with terrestrial pests, such as deer and even bears. However, the patent application has yet to be approved, calling the invention into question.

Because of the sharks' sensory organs and the dilution of capsaicin in the water, it doesn't seem likely that the pepper spray would deter the fish. Their noses don't open into their respiratory systems like humans, meaning any spicy water would not enter through the nostrils [source: Parker]. They also wouldn't ingest the water because they extract oxygen from it then release it through their gills [source: Parker]. Finally, their eyes have dual eyelids and a protective membrane to keep their peepers safe.

The Discovery Channel's dynamic duo of science, Jamie and Adam of MythBusters, closed the book on this question when they tested this theory with capsaicin extracted from the fiery habanero pepper inside of a bio-degradable balloon. Even though the peppers pack a powerful punch, it wasn't enough to scare away any sharks.

But these results aren't that surprising considering the amount of noxious chemicals sharks can withstand. For example, one experiment to find a poison capable of killing a shark ended in 29 misses [source: Parker]. Strychnine was the only thing that did the job, and even that took eight minutes to work [source: Parker].

Fortunately, shark attacks are a statistically rare occurrence, and there are many things you can do to help avoid encounters and to fend them off when you come face to face.

For more information about shark defense and other shark-related topics, dive into the links below.

Related HowStuffWorks Articles

More Great Links


  • Andrews, Jean. "Peppers: The Domesticated Capsicum." University of Texas Press. 1995. (June 13, 2008)
  • Bavley, Alan. "Ancient eaters liked it hot, too: Chilies date back 6,000 years, making them one of the oldest domesticated foods in the Americas." Knight Ridder Tribune Business News. Feb. 16, 2007. (June 11, 2008)
  • Brown, David. "One Hot Archeological Find." The Washington Post. Feb. 16, 2007. (June 11, 2008)
  • Hussein, Wasbir. "World's Hottest Chili Used as Elephant Repellent." National Geographic. Nov. 20, 2007. (June 11, 2008)
  • Matos, Gonzalo Ramos and Romero, Felix Eduardo. "Capsicum shark repellent." United States. Application number 11/179,118. July 12, 2005. (June 11, 2008)
  • Parker, Jane and Parker, Steve. "The Encyclopedia of Sharks." Firefly Books. 2002.
  • Perry, Linda and Flannery, Kent V. "Precolumbian use of chili peppers in the Valley of Oaxaca, Mexico." July 17, 2007. (June 11, 2008)