In season 3 episode 2 of Survivorman, Les Stroud explains that red snow will make you sick. He also says that he doesn't know why it makes you sick. What's in it that makes you sick?

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  • 3
    No obligatory 'yellow snow' joke yet? 🤔
    – OddDeer
    Commented May 15, 2018 at 10:48

1 Answer 1


Watermelon snow is caused by algae called Chlamydomonas nivalis. Apparently, it has laxative effects.

As Giersch and National Park representatives explain, the red pigment in the algae helps to protect its chloroplast from the sun’s radiation, allowing it to take in more heat. As the algae absorbs the sun's heat, it causes the snow around it to melt, feeding the algae with water and allowing it to continue thriving as it settles into deposits in the snow.


That being said, NPS representatives strongly advise against any temptation to taste the sweet-smelling ice, as scientists warn that watermelon snow can cause disruption to your digestive system.

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Scientists, however, warn us not to eat watermelon snow because of its laxative effects.

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That being said, it's usually concentrated in areas and I have never had a choice between watermelon snow and no water.

  • Can you discuss whether or not boiling watermelon snow sanitizes it?
    – Felix
    Commented May 15, 2018 at 12:30
  • 1
    @Felix - The algae would release a toxin into the snow. I would expect boiling to kill the algae, but leave the toxin. Commented May 15, 2018 at 12:39
  • @Felix I don't think there would be a reason to, it never covers all of the snow. Commented May 15, 2018 at 14:09

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