If music festival revellers knew where dealers kept drugs before they sold them they would nearly vomit, a Sydney hospital emergency department director says.

Dr Gordian Fulde, from St Vincent's Hospital, made the comment after a 23-year-old woman was admitted in a critical condition following an overdose during the Field Day music festival in Sydney's CBD on New Year's Day.

The 23-year-old's condition has since improved and she was released on Saturday.

Drug use at festivals has been under the spotlight since a 19-year-old man died in Adelaide and a 25-year-old woman died in Sydney at the Stereosonic music events.

Dr Fulde said there was a trend over the last year or two of more women using ecstasy.

"If they knew where they had come from, where people had concealed them, a lot of people would nearly vomit, I believe," he said.

"And that's one of the ways they do it: they swallow it and then the person vomits up the plastic balloon with all the pills in it and somebody buys it, which is pretty insane."

Dr Fulde said drug overdoses could have devastating consequences.

"The patients who came to us mainly had taken pills but we had a couple of patients who actually came to grief from trying to transport pills by ingestion and other means, hidden from the police and the dogs into the venue," he said.

He said young people who suspected they had overdosed needed to seek help immediately.

"They're frightened their parents will find out," he said.

"They're frightened we'll tell the police. We don't do any of that.

"As far as I'm concerned bring your friend, call the ambulance, take them to the medical tent — which all festivals now have — and you don't have to give your real name, but if we get to these patients early they won't die."

'You don't need drugs to enjoy music', doctor says

During the Field Day event, 212 people received medical treatment by paramedics and five of those were taken to hospital.

The police operation at the event, held at The Domain in Sydney, targeted anti-social behaviour, alcohol-related crime, and illegal drug possession and supply.

Police charged 184 people with alleged drug offences, including eight for drug supply.

Police say a 26-year-old woman was found carrying 100 ecstasy capsules and a 19-year-old was found with 81.

They were both charged with supplying drugs and granted conditional bail to appear at Downing Centre Local Court later this month.

Dr Fulde said he believed education needed to be focused on primary school aged children.

"I really think the focus has to be on the younger generations, and I mean kids less than 10, because that's our hope," he said.

"The current generation is probably not going to change that much. You don't need to take drugs, you don't need to take mind-altering substances to enjoy something as fabulous as good music — there's other young people, there's dancing."