Shark Attacks and Menstruation: Debunking the Myth

There is zero scientific evidence that menstruation increases shark attack risk. This pervasive myth stems from the false premise that sharks are attracted to human menstrual blood.

What Sharks Actually Detect

• Amino acids, bile acids, urea, electrical fields from prey (fish, seals, marine mammals) via olfactory bulbs (detect 1 part per billion) and ampullae of Lorenzini.
• Human blood is chemically distinct from marine prey blood; no evidence it’s a specific attractant.
• Menstrual fluid is not just blood—it’s endometrial tissue, cervical mucus, vaginal secretions, and ~30–80 mL total over days. Dilution in ocean is instantaneous.

Evidence

• No epidemiological correlation between menstruation and shark bites (International Shark Attack File, 1958–present).
• Controlled studies: sharks ignore human blood/blood components; respond to fish extracts.
• Most attacks: mistaken identity (surfers = seal silhouette), investigative bites, territorial.

Real Risk Factors

• Time/location: dawn/dusk, near seal colonies, river mouths, steep drop-offs.
• Activity: surfing, spearfishing (bait), swimming alone.
• Appearance: high-contrast clothing, shiny jewelry (fish scales).
• Behavior: erratic splashing, bleeding wounds (not menstrual).

Practical Advice

• Menstruate without fear—use tampon/cup/disc if preferred.
• Follow local shark safety guidelines (flags, spotters, closures).
• Don’t swim with open wounds (any blood).
• Swim in groups, avoid high-risk times/areas.

The ocean is sharks’ home. Respect it; don’t fear a biological myth.