From a cloth dye to a hospital drug to a supplement shelf, in eight moments.

• BASF made it as a wool dye in 1876. Heinrich Caro created it, and dye grades are still made today for textiles, labs, and aquariums.
• It is credited as the first fully synthetic drug used in clinical medicine. In 1891 Ehrlich and Guttmann treated two malaria patients in Berlin with it.
• Most of its safety data comes from hospitals. Doctors have used it for methemoglobinemia since 1933, and the FDA approved Provayblue for that use in 2016.

Important: Methylene blue has documented interactions with serotonergic medications including SSRIs and MAOIs. Review the full adverse medications list before starting any methylene blue protocol.

In 1876, a chemist named Heinrich Caro created a new blue dye for wool at BASF in Germany. A year later it became the company's first patent for a coal tar dye, according to BASF's own history.^[14]

It is worth starting here because the dye world never went away. The same molecule is still made today for textiles, laboratories, and aquariums, and none of those grades is meant to be swallowed.

When you read the word USP on a label, it is the line between that industrial history and something made for people.

Methylene blue clings to some parts of a cell and ignores others. Under a microscope, that made invisible structures suddenly visible.^[14,2]

By 1886, Paul Ehrlich was using it to stain nerve cells and the parasite that causes malaria. Watching a dye find one target and leave the rest alone gave him an idea that shaped modern medicine: if a dye can seek out one kind of cell, a compound could be built to seek out a disease.

He called it a magic bullet. Five years later, methylene blue became his first attempt at one. Labs still use it as a stain today.

In 1891, Ehrlich and Paul Guttmann treated two patients with malaria in Berlin using methylene blue. A 2018 systematic review in BMC Medicine describes it as generally credited as the first fully synthetic compound used in clinical medicine.^[15,2]

Before that moment, medicines came from plants, minerals, and animals. After it, chemists knew they could build one from scratch.

Quinine was already available and eventually won out for malaria, but methylene blue had already changed how people thought about drugs.

Chemists studying methylene blue's structure found the phenothiazine ring at its core. According to the Schirmer review, that ring became the starting point for some of the first antipsychotic medications and, later, the tricyclic antidepressants.^[2,1]

This family connection is not just trivia. It is part of why methylene blue interacts with the brain's chemistry, and it is why the FDA label for Provayblue carries a boxed warning about combining it with serotonergic antidepressants.

Module 7 covers that warning in full. For now, remember that methylene blue is the grandparent of a whole branch of psychiatric drugs.

In 1933, physicians documented methylene blue reversing methemoglobinemia, the blood condition where hemoglobin cannot carry oxygen properly. Within a few years it was the standard treatment, and it still is.^[2,12]

Surgeons also began using it as a dye inside the body, tracing lymph nodes and helping locate the parathyroid glands during operations, because it stains some tissue and not others. That is the same property Ehrlich noticed in 1886.

These hospital uses are where most of the safety data on methylene blue comes from. StatPearls summarizes them, along with the amounts used, which you will see in Module 6.

During World War II, Allied troops in the South Pacific took methylene blue to prevent and treat malaria, according to the Schirmer review. It came with side effects every soldier noticed.^[2]

It turned their urine green and the whites of their eyes blue. The effects were harmless, but troops disliked them enough that methylene blue fell out of favor as an antimalarial.

That blue and green urine still happens today. It is simply the compound leaving the body, and Module 4 explains exactly why.

In 2016, the FDA approved Provayblue, a branded methylene blue injection, for acquired methemoglobinemia. It was the first approved therapy for that specific condition, even though hospitals had used methylene blue for it for more than 80 years.^[1]

The label that came with the approval is the most detailed public safety document on methylene blue. It lists the warnings, the interactions, the side effects, and how the body handles the drug.

Whenever this course talks about safety, the FDA label is usually the source. It describes a hospital product, not a supplement, but the molecule is the same.

Research through the 2000s and 2010s looked at what small amounts of methylene blue do inside mitochondria. That work reached a wider audience in the 2020s, and supplement versions started to appear.^[16]

Nutricel began in 2020, when a father and son were caring for family members and could not find a methylene blue product they trusted. In December 2022 they listed what we believe was the first methylene blue capsule on Amazon.

Since then the category has exploded, and quality has not kept pace. Module 8 shows what our testing found.

Methylene blue has been a dye, a stain, a malaria drug, and a hospital medicine. Supplements are the newest chapter, and the old dye trade is the reason the grade on a label still matters.

• 1877: BASF patented Caro's dye, its first patent for a coal tar dye.
• 1886: Paul Ehrlich used it to stain nerve cells and the malaria parasite, which led to his magic bullet idea.
• Its phenothiazine core became a starting point for early antipsychotics and later the tricyclic antidepressants.
• In WWII, Allied troops in the South Pacific took it for malaria and disliked the green urine and blue eyes it caused.
• The 2016 Provayblue approval came after more than 80 years of hospital use.

Clinical and regulatory

Peer-reviewed research and history

Nutricel testing and data