Mr. Yuk is a grimacing, sickly green face with its tongue sticking out, as if it had just tasted something disgusting. These stickers are widely used across the United States as children's warning labels on household poisons, and can be obtained from your local poison control center.

Mr. Yuk was designed in direct contrast to the happy yellow "Have a Nice Day!" stickers from the 1960s, and are intended to replace the old "skull and crossbones" symbol that had previously been used to mark poisons. Research has shown that children were actually attracted to the skull and crossbones symbol, interpreting it as marking the contents as pirate food. Mr. Yuk, on the other hand, has proven to be a much more effective deterrent because it clearly has no meaning other than "this tastes gross!".

Mr. Yuk stickers should be placed on all household poisons when there are small children around, and parents should be clear about its meaning. It is important to remember, though, that this is a back-up measure. The primary method of preventing accidental poisoning should always be keeping household chemicals out of reach of children in the first place. Cleaners should not be kept under the sink or in any other low storage area, unless the cabinet doors have a child proof lock.

Mr. Yuk was designed by the Pittsburgh Poison Center at Children's Hospital of Pittsburgh in 1971, but his history can be traced back to 1927 with the passing of The Federal Caustic Poison Act, which requires all poisonous materials to be labeled as such. This act was the personal project of Dr. Chevalier Q. Jackson (1865-1958), one of the United States' leading laryngologists, who observed and treated hundreds of children who had suffered life threatening throat injuries from eating lye. Lye was packaged in a similar manner to sugar at the time, and even looked a bit like sugar, and had no markings whatsoever to warn children or their parents just how dangerous it could be to ingest. Tragically, some children's throats were so badly damaged that they could no longer eat and slowly starved to death. Mr. Yuk is a direct result of Dr. Jackson's national campaign to educate the public about the dangers of household chemicals, and uncountable accidents and deaths have undoubtedly been prevented as a result of his efforts.

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ASCII Mr. Yuk found at

momomom adds: Poisons should always be kept in their own original containers — this provides reliable information for poison control if an accident occurs as well as reduces the chance of a child taking it by accidental association.
Thanks momomom! I'll also note that this is part of the OSHA requirements on storing chemicals in the workplace (either leave them in their original containers or store them in a well-marked container that has never been used to store food items).

And thanks to arcanamundi for telling me I had this spelled incorrectly.

Sources: (Thanks generic-man!)