Why is Poison Blue?

Blue poison dart frog/ istockphotoLeyton’s blog yesterday which featured pictures of strange trays filled with blue rodenticide got me wondering why poison is blue?

Poison dart frogs are some of the most brilliant and beautiful colors on Earth. Depending on individual habitats, which extend from the tropical forests of Costa Rica to Brazil, their coloring can be yellow, gold, copper, red, green, blue, or black. Their elaborate designs and hues are deliberately ostentatious to ward off potential predators, a tactic called aposematic colouration. They are very pretty but one touch could prove deadly.

Blue victorian poison bottles/istockphotoThe poison dart frog wasn’t officially discovered until 1968 but the Victorians also used the colour blue to signify poison. In the mid 1800’s, poisonous substances came onto the market to rats, mice and weeds. To prevent mishaps, poison bottles were given distinctive features. Colors like cobalt blue, black, and dark green ensured they were easily recognizable. So did raised lettering or inlays of the words ‘POISON’ or ‘DEATH’ (especially useful if you were fumbling by candlelight).  Some bottles were shaped like coffins or skulls and are rare collectors items.

Rentokil Rodenticide - spooky blue ice cubes!

Rentokil Rodenticide - spooky blue ice cubes!

Today, we use blue in our rodenticides as it is an unnatural colour and signifies danger. Bitrex is an ingredient which makes it unbearable for humans to eat. Rats will literally eat anything, and couldn’t care less about the colour.

  1. marcel

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