Films portraying evil characters as having visible differences, such as scaring or disfigurement, should include a warning about stereotyping.
British charity Changing Faces is calling on streaming platforms such as Netflix, Amazon Prime, Apple TV and Disney+ to make the change.
Changing Faces Chief Executive Heather Blake told Moncrieff Halloween is a particularly stressful time for some people.
"We're pointing out the link in so many films and TV series between scaring and other forms of visible differences being used as a short-hand for villainy," she said.
"It's particularly apparent at Halloween, which is why we're talking about it now, in films and also in costumes that people dress up in".
'Normalising appearances'
Ms Blake said it has a real impact on people who live with scars or other conditions.
"Their appearance gets associated with something to be scared of," she said.
"We have been calling for better representation in films and TV; so more people with visible differences in roles that aren't the villain.
"They could be the hero, the best friend or even just the bystander - so really normalising these appearances.
"We are starting to see a little bit of that happening now but it's very slow.
"We're therefore also now asking that there should be recognition that where films contain negative portrayals of people with visible differences, that there should be a recognition upfront of the negative impact of that."
Educating people
Ms Blake said such a caveat could also be used to help educate people.
"We don't want to stop people watching these films we just want more people to be aware of the stereotype and how it might be affecting behaviour in real life," she said.
"We'd want to talk to the platforms about exactly what it might look like.
"It might be something like, 'This film contains a harmful stereotype where scars, marks or conditions are used to denote villainy'.
"Then maybe give people a pointer on where they can find out more about the issue, and use it as an opportunity to educate people.
"Particularly, also, we'd want to signpost to where people could get support if they're affected themselves," she added.
