Despite viral videos, methylene blue won't improve your mood or cognition, experts say

CBC

11-05-2025

A chemical first synthesized in the 1800s as a textiles dye is making the rounds on social media as an easy way to boost mood and enhance cognition. However, experts say it's only really useful in treating very specific medical conditions, most notably a rare blood disorder called methemoglobinemia.
Methylene blue received significant social media attention after a video began circulating in February showing U.S. Health and Human Services Secretary Robert F. Kennedy Jr. using a dropper to add a blue liquid to a glass of water.
"To anyone who knows anything about chemistry, you look at that video and it's very clear that he's squirting methylene blue into the glass," said Joe Schwarcz, director of McGill University's Office for Science and Society, speaking with Dr. Brian Goldman, host of The Dose podcast.
Health and wellness influencers, including podcasters like Joe Rogan, quickly began suggesting that, taken orally, methylene blue could be used to improve cognition, minimize the signs of aging and even — in the case of controversial filmmaker Mel Gibson — fight cancer.
Despite the attention it has received, experts say that people shouldn't take methylene blue unless under the supervision of a medical professional.
What is methylene blue?
First synthesized in the late 1800s by German chemist Heinrich Car o, methylene blue began its life as a textiles dye. But it was soon discovered it could stain microbes under a microscope, making them easier to see and study.
After methylene blue was found to not only stain but actually kill one of the parasites that causes malaria, the dye took on a new life as a treatment for the mosquito-borne disease, Schwarcz says.
"It competed with quinine, but it was much cheaper to produce," said Schwarcz, who has a PhD in chemistry and also teaches at McGill.
"By playing around with the molecular structure, sort of molecular roulette, [chemists] were able to change the structure of the molecule eventually into chloroquine, which is still widely used today to treat malaria."
Because of this, methylene blue remains on the World Health Organization's Model List of Essential Medicines.
How else is methylene blue used today?
Modern physicians now mostly know it as a treatment for methemoglobinemia, a rare condition that occurs when the blood is unable to adequately carry oxygen throughout the body.
"Methylene blue is effective at … helping them restore the balance to a normal amount of oxygenated hemoglobin or deoxygenated hemoglobin," said Dr. Emily Austin, a Toronto-based emergency physician and medical director of the Ontario Poison Centre.
Drugs like dapsone, used to treat leprosy and certain kinds of dermatitis, as well as substances like amyl nitrites — found in party drugs like poppers, as well as in soil runoff contaminated by fertilizers — can cause methemoglobinemia.
Topical anesthetics can also sometimes cause chemical changes in the body that lead to methemoglobinemia, says Austin.
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Symptoms of methemoglobinemia include blue lips or blue fingertips, shortness of breath, confusion and fainting. Patients may even have a distinct chocolate colour to their blood.
Austin says methemoglobinemia is relatively rare, and she has seen it only once since she began working as an emergency physician in 2016, though she adds that the condition is seen more frequently at the Ontario Poison Centre.
"In general, it's still a fairly rare occurrence," said Austin.
"This is not something that somebody would necessarily see in their career as a practising emergency physician, although it's common enough that I think it's important we have an approach to it."
Is there anything to the claims methylene blue can prevent Alzheimer's?
Some social media claims have suggested methylene blue can be effective in preventing and treating Alzheimer's disease.
Schwarcz, however, says the link between methylene blue and Alzheimer's is more complicated than Tiktok might suggest.
One of the telltale neurological signs of Alzheimer's disease is the tangling of tau proteins in the brain.
"It turns out that methylene blue was not only able to visualize and stain those tangled proteins that characterize Alzheimer's disease, but, amazingly, under the microscope … it actually untangled those proteins," said Schwarcz.
However, research has shown that ingesting methylene blue orally does little to improve symptoms of Alzheimer's.
What has shown some promise in very early research on animals, Schwarcz said, is a derivative of methylene blue created by altering its molecular structure.
"There have been a couple of pilot studies on humans where it seems that the deterioration in terms of Alzheimer's was slowed down somewhat," he said.
"But we need a lot more work there."
A 2023 comprehensive review of randomized control trials examining the effects of methylene blue and its derivatives on Alzheimer's treatment highlighted the compound's "potential to improve cognitive function, reduce oxidative stress, and protect against neurodegeneration."
Nonetheless, the same paper pointed out several concerns, among them safety issues and adverse effects — including mild to moderate gastrointestinal and urinary effects — while simultaneously highlighting the need for studies with larger sample sizes, longer treatment durations and an examination of proper dosages and administration routes.
For his part, Schwarcz says not only does the commercially available methylene blue bear little resemblance to the derivative included in that research, there's little benefit to taking it until better, longer-term research shows that it actually can improve brain health.
"I can't say that there's no long-term risk, because no one has ever studied this over the long-term," said Schwarcz.
Methylene blue and SSRIs
Austin, however, says people taking selective serotonin reuptake inhibitors (SSRI), a class of medication typically used to treat depression, should avoid consuming methylene blue.
That's because taking it along with SSRIs inhibits the breakdown of serotonin, and can lead to a condition known as serotonin toxicity, says Austin.
Serotonin is a neurotransmitter that, among other functions, plays a role in regulating mood, cognition and memory.
Too much serotonin circulating in the body — sometimes called serotonin syndrome — can lead to higher or lower heart rate, high blood pressure, increased body temperature, as well as changes in the behaviour of muscles and reflexes, Austin says.
She says concerns around serotonin toxicity are one of the reasons why she might avoid treating her patients with methylene blue.
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Poor scientific literacy behind proliferation of health misinformation
As someone who regularly works to combat health and other scientific misinformation, Schwarcz says a lack of scientific literacy is one of the reasons why social media users easily spread dubious information about methylene blue and other topics.
"They don't understand the underlying science, and they will make mountains out of molehills," said Schwarcz.
"Unfortunately, this is just the way things are working these days. Social media has taken over information spread."
At the same time, Schwarcz blames public figures like Robert F. Kennedy Jr. for aiding in the spread of misinformation.