Animal dewormer and a drug used to treat scabies are being sold and promoted as unproven cancer treatments, a BBC investigation has found.

Following a tip off, an undercover journalist was able to buy fenbendazole and ivermectin from a stairlift salesman in south Wales and also found them for sale on Amazon.

Macmillan Cancer Support said it was concerned by the findings and that a growing number of people were asking about the medicines, despite “no clinical evidence” that they work.

Amazon removed the products after we contacted them, and said it had “proactive measures in place” to stop prohibited products being listed by third-party sellers.

Senior doctors are worried vulnerable patients could be put at risk by taking the medicines, as they say it could harm or delay conventional treatment.

Six months ago, Rebecca Holder contacted the BBC after a visit from stair lift salesman Jason Sarver.

She said Sarver and her father Bob, who had a brain tumour, lung cancer and needed help with his mobility, had been discussing stair lifts when the salesman changed the topic to talk about the drugs.

Ivermectin is an anti-parasitic drug used to treat conditions like scabies, while fenbendazole is an animal dewormer.

The BBC has seen videos and social posts with thousands – sometimes millions – of views, with unproven claims that these medicines could help treat cancer.

Hollywood actor Mel Gibson claimed on a popular US podcast that the drugs successfully treated three of his friends who had cancer.

“Jason started to say that he could get hold of a treatment that wasn’t available on the NHS, that was known to shrink brain tumours,” Rebecca said.

“So I wrote down everything he said about these medicines…fenbendazole, ivermectin…I couldn’t quite believe what he was saying.”

Rebecca said Sarver offered to sell her dad, from Monmouthshire, the medicines.

An undercover BBC reporter contacted Sarver posing as someone with a relative who had cancer.

He repeated the same claims, and sent a link to videos making unproven assertions that the drugs were effective against cancer.

“I do a lot of research, medical papers, white papers, anything that comes out fresh, I am on it,” Sarver said.

“I’m not a doctor, I just passed what I hear on.”

He went on to supply the BBC with fenbendazole and ivermectin tablets for £100 which he said would be “two to three months’ supply” to treat lung cancer and “other cancers as well”.

He said his work selling stair lifts meant he saw “a lot of ill people”.

“I can’t help myself, I’ve got to tell them about it,” he said.

Ivermectin is a prescription-only medicine in the UK, which means it can only be given by a licensed person, such as a doctor or pharmacist.

It gained global attention as a potential “miracle drug” during the coronavirus pandemic, although clinical trials have consistently shown it does not provide clinical benefits for Covid-19 patients.

The MHRA medical regulator said it was not licensed for cancer treatment.

Animal dewormer fenbendazole is an anti-parasitic drug which is not licensed for use in humans in the UK.

It can be bought in small quantities for animals without a prescription, according to the Veterinary Medicines Directorate.

While some trials exist into their anti-cancer properties, Macmillan Cancer Support charity said there was “zero real-world clinical evidence” to back up the claims about ivermectin.

The charity’s chief medical officer, Prof Richard Simcock, said he was concerned the BBC was able to easily buy the medicines without a prescription.

“We’re seeing an increasing number of people asking about these two products,” he said.

“We’re worried that they’re not getting up-to-date and effective and accurate information about what these drugs are capable of.

“If someone is thinking about taking these drugs, we’d really urged them to talk to their clinical team or ring the clinical helplines at Macmillan where we can provide information about what safe and effective care might look like.”

He added this kind of misinformation was often fuelled by the appeal of personal anecdotes, especially if they came from someone a person already knows.

Cancer Research UK also warned that, while there was some anti-cancer data from testing fenbendazole using mice, there was no scientific evidence to prove that it worked in people.

Jared Wright, from Wisconsin in the USA, told the BBC that his mother Kelly started taking ivermectin and fenbendazole after being diagnosed with cancer last year.

He said she ignored doctors’ advice to accept conventional treatment and became a “victim of misinformation about cancer”, putting her faith in the drugs in the hope of a cure.

“They were delivered to our house, these pill bottles, and she just started eating the ivermectin and the fenbendazole three times a day,” Jared said.

“All she had read online was that it cures cancer.”

Jared said his mother died shortly after her 63rd birthday in January this year.

“It was a horrible death. She was shaking, she couldn’t see, she had this glaze over her eyes, she couldn’t speak anymore,” he said.

“She had another 20 years or more – she would be alive right now if she had the correct information, if she had listened to me and gone to an oncologist.”

The BBC discovered it was easy to get hold of the drugs that Kelly hoped would save her.

We found multiple websites offering delivery to UK addresses and successfully made several orders with Amazon.

Supplying prescription-only medicines is an offence under the Human Medicines Regulations 2012 unless you are an “appropriate practitioner” such as a doctor or a pharmacist.

The MHRA said, where there was evidence that a veterinary medicine is supplied for humans or a prescription-only medicine is sold by someone other than a qualified healthcare professional, it could take enforcement action, including criminal investigation and prosecution.

Since 2024, it has seized 27,500 doses of fenbendazole and 124,000 doses of ivermectin intended for human use, working in conjunction with Border Force.

Martin Rolles, a consultant oncologist with 25 years of experience at the South West Wales Cancer Centre, warned the drugs could interact with proven cancer medication and either make treatment more toxic or less effective.

“There’s also the risk that the drugs themselves could cause side effects and make the patient unwell, which might stop them being able to receive conventional cancer treatment,” he said.

He added the reason ivermectin was not part of conventional treatment was because there were “no good human trials…for use against cancer”.

“There’s certainly some interesting laboratory data but that’s not the same as clinical evidence,” he said, adding there was not enough data on fenbendazole as a cancer treatment, so “therefore it is unsafe”.

Three-time cancer survivor and former surgeon Liz O’Riordan now uses YouTube to answer cancer questions and challenge conspiracy theories.

She said she knew of people dying after believing anecdotes about unproven cancer treatment.

“Anecdotes and testimonials are now the strongest forms of evidence – ‘my aunt on Facebook did this, therefore it must be true’,” she said.

“You don’t know their medical records, they could be having other treatment as well.

“I see the other side, I see the people where it doesn’t work, where they got sick, where they died.”

She continued: “It’s that fear of death – you want control, you want hope, you want to be that one person who’s going to make it.

“I just worry it’s getting bigger and if we don’t all take notice and start to do something about it, we’re going to be in a very dark place in a couple of years’ time.”

The BBC contacted Jason Sarver to ask about why he sold the drugs, but he declined to comment.