Hospitals are being urged not to decorate children's wards with paintings of clowns in case they upset young patients.
State-funded research has found that in a survey of more than 250 children aged four to 16, all disliked the use of clowns in hospital decor, with even the teenagers seeing them as "scary."
"Given that children and young people do not find hospitals frightening per se - and only express fear about those spaces associated with needles - this finding is somewhat ironic," said Dr Penny Curtis of Sheffield University.
The fear of clowns, known as coulrophobia, can cause panic attacks, shortness of breath, irregular heartbeat, sweating, nausea and feelings of dread. It is one of the 10 most searched-for phobias on Yahoo! search engine.