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Myth vs fact

Let’s clear up what people often get wrong about periods — today and throughout history.

Illustration of a magnifying glass over a phone calendar, surrounded by crossed-out myth symbols

Today

Modern myths

Things people still believe now.

  • Myth: You can’t exercise on your period.

    Fact: Movement is safe, and a Cochrane review found regular exercise can reduce period pain. Go gentle if your energy is low.

  • Myth: Periods should be kept secret.

    Fact: Talking openly removes shame and helps people get support and care.

  • Myth: PMS is “all in your head.”

    Fact: Hormone shifts in the luteal phase can genuinely affect mood, sleep and appetite.

  • Myth: Every cycle is exactly 28 days.

    Fact: 21–35 days can be normal. In data from over 600,000 cycles, only about 13% were exactly 28 days.

  • Myth: Periods are only a women’s topic.

    Fact: Partners, fathers and friends all benefit from understanding the cycle.

Illustration of an ancient Greek vase, a scroll, a wilting flower, a wine cup and a crescent moon

History

Ancient myths

For thousands of years, people explained periods without science — and fed the stigma that still exists.

  • Ancient Rome: periods sour wine and kill crops.

    In his Natural History (around 77 AD), Pliny the Elder claimed a menstruating woman could turn wine sour, make crops wither, dull mirrors and blunt knives. Fact: menstrual blood is blood and tissue from the uterine lining. It has no such powers.

  • Ancient Greece: the “wandering womb”.

    Greek medical writers believed the womb could move around the body and cause illness, and that regular bleeding was needed to purge “excess” blood. Fact: the uterus stays in place. Periods happen because hormone levels fall when no pregnancy occurs.

  • Aristotle: period blood is the raw material of babies.

    Aristotle taught that a baby formed when male seed shaped menstrual blood, with women providing only passive matter. Fact: a baby forms from an egg and a sperm, each contributing half of its DNA.

  • “Menotoxins”: periods are poisonous.

    As late as 1920, a doctor claimed flowers wilted when handled by menstruating women, and the idea of a “menstrual toxin” lingered in medicine for decades. Fact: later research found no such toxin.

  • Many cultures: periods make you impure.

    Across many religions and traditions, menstruating women were kept away from kitchens, temples or their own homes. Practices like Nepal's chhaupadi still put girls at risk today. Fact: periods are a healthy, normal body process, not a sign of uncleanness.

Ask Aunt Flo