|This section does not cite any references or sources. (December 2011)|
In order to help children learn to avoid ingesting poisons, Mr. Yuk was conceived by Dr. Richard Moriarty, a pediatrician and clinical professor of pediatrics at the University of Pittsburgh School of Medicine who founded the Pittsburgh Poison Center and the National Poison Center Network. In Pittsburgh, the skull and crossbones previously used was not terribly helpful, because the Jolly Roger was the mascot for the local baseball team, the Pittsburgh Pirates.
The color was chosen when Moriarty was showing different colors to students, and the green that was chosen was christened "Yucky!" by a young child. Hence, the name and the color. The design for Mr. Yuk was created by Wendy Courtney Brown, then a 4th grade student at Liberty Elementary in Weirton, West Virginia, as part of a Pittsburgh Poison Control design contest.
Over time, the use of Mr. Yuk stickers has gained a certain amount of nationwide usage in the United States. Mr. Yuk stickers usually contain phone numbers of poison control centers that may give guidance if poisoning has occurred or is suspected. Usually, stickers may carry a national toll-free number (1-800-222-1222 in the United States). In some areas, local poison control centers and children's hospitals issue stickers with local numbers, under license. Such an example is in Pittsburgh, where the telephone number for the Poison Control Center is 681-6669.
A memorably scary public service announcement was also produced in the 1970s featuring the theme song, becoming a popular culture icon unto itself for a number of generations.
The Mr. Yuk symbol has been used as a replacement for the traditional skull-and-crossbones (a.k.a. Jolly Roger) warning label for poison. Since children may associate this symbol with pirates, the symbol may be less effective at deterring ingestion.
To evaluate the effectiveness of six projected symbols (skull-and-crossbones, red stop sign, and four others), tests were conducted at day care centers. Children in the program rated Mr. Yuk as the most unappealing product. By contrast, children rated the skull-and-crossbones to be the most appealing.
However, at least two peer-reviewed medical studies (Fergusson 1982, Vernberg 1984) have suggested that Mr. Yuk stickers do not effectively keep children away from potential poisons and may even attract children. Specifically, Vernberg and colleagues note concerns for using the stickers to protect young children. Fergusson and colleagues state that “the method may be effective with older children or as an adjunct to an integrated poisoning prevention campaign.”
Mr. Yuk and his graphic rendering are registered trademarks and service marks of the Children's Hospital of Pittsburgh of UPMC, and the rendering itself is additionally protected by copyright. This means that the name and graphic image cannot be used without a license from the owner—unlike the skull and crossbones symbol, which is in the public domain.
The Children's Hospital of Pittsburgh of UPMC gives out free sheets of Mr. Yuk stickers if contacted by mail.
Mr. Yuk materials can also be ordered online from the University of Pittsburgh.
- Mr. Yuk has taken on a cult status throughout the city of Pittsburgh among older residents, the best example being the Ultimate Frisbee team at Carnegie Mellon University, which affectionately goes by "Mr. Yuk" and uses a variety of discs adorned with the classic logo.
- Additionally, another "Mr. Yuk" team has sprung up. The ice hockey team. Full of beast, this team ravages on the the highest division of the Pittsburgh Sports Arena. Fans chant "Mr. Yuk means no! Stay Away!" at opposing teams as they leave the ice beaten both mentally and physically. 
- An image of Mr. Yuk is featured in the video game Call of Duty: Modern Warfare 2 inside the lens cap of the Walther WA 2000 sniper rifle, as well as the Barrett M82 sniper rifle, where the sticker is rotated 90 degrees counter-clockwise. It also appears as the image for receiving "bad" accolades.
- In the computer game Civilization IV, cities with illness emit green smoke and have the Mr. Yuk sign by their name.
- "Adult Programs". Carnegie Museum of Natural History. Retrieved February 14, 2013.
- Washington Poison Center
- Vernberg K, Culver-Dickinson P, Spyker DA. (1984). "The deterrent effect of poison-warning stickers". American Journal of Diseases of Children 138, 1018–1020. PMID 6496418
- Fergusson DM, Horwood LJ, Beautrais AL, Shannon FT. (1982). "A controlled field trial of a poisoning prevention method". Pediatrics 69, 515–520. PMID 7079005
-  Website for CMU men's ultimate team]
- Mr. Yuk Information Page
- Short discussion of Fergusson and Vernberg papers
- American Association of Poison Control Centers
- Acceptable Labelling on Pesticide Containers
- Original Mr.Yuk Public Service Announcement On YouTube
- History of the creation of Mr. Yuk