In the case in point, US-based toy giant Hasbro secured a notable victory last Friday in the High Court, England and Wales, in its trade mark infringement and passing off action against 123 Nährmittel and its UK supplier MAPS Toys. At the heart of the dispute were the questions whether (i) the defendants' use of the words "play dough" on their YUMMY DOUGH, in the phrase "the edible play dough" product, infringed Hasbro's PLAY-DOH trade mark and (ii) whether PLAY-DOH was even validly registered or should in any event be revoked. Mr Justice Floyd gave judgment in favour of Hasbro, finding that the defendants did not act in accordance with honest practices in industrial and commercial matters.
BAILII, but he has been able to procure a copy of the 52-page judgment, the product of eight days in court and some careful thought on the part of the judge as to the manner in which he described and listed the considerations relevant to the fairness of the defendants' use. Considering how descriptive the words "play dough" are, when taken as a term for a doughy product with which you play, crossing the line between a responsible, sensible descriptive use and one which seeks to gain some benefit from a registered trade mark which sounds much the same actually takes some going. You can read the full text of the judgment here [nb this is a replacement link: the earlier version had the illustrations in black and white only, and careful readers would have detected the absence of a couple of pages]. Paragraph 228 lists the ten relevant considerations which led the judge to conclude that
"... the defendants proceeded on the basis that, in their opinion 'the edible play dough' was a descriptive term and that, accordingly, Hasbro would find it impossible to stop them, no matter what use they made of it. They did not consider whether making it part of the name of the product would have different implications. They did not consider it relevant to consider whether, to others, 'the edible play dough', in the particular context in which they were using it on their packaging and within the toy trade, would mean the Hasbro product, or amount to taking advantage of Hasbro's goodwill, and ignored warnings to that effect".Edible play dough recipes here and here
Health hazards of play dough here
The constitutional role of play dough in the United States here