For centuries, common bleach has been used to slay nasty bugs, from flu to Ebola. But we didn't learn its lethal secret until 2008

A terrifying thought exercise: Imagine the world’s most lethal countertop. It looks completely normal with the naked eye, but is in fact populated with a panoply of the deadliest pathogens on Earth. There’s influenza, a naval mine-looking virus capable of everything from a few days in bed to killing millions around the globe. There’s smallpox, arguably the king of all the little beasts, oblong with a core membrane that evokes brown recluse spiders and cellos. There are the viperine knots of the much-feared viral hemorrhagic fevers, most famously Ebola and Marburg, modern maladies which practically liquify their victims until they bleed and crash out. There’s clostirdium dificile, commonly known as C. diff, an extraordinarily hardy pill-shaped bacteria that plagues hospitals, causing diarrhea, severe abdominal pain, and renal failure, and which can form almost impossible-to-stop spores. And, then there is arguably the hardest to kill microorganism of all: a twisted little corkscrew impossibly tiny even in this miniature menagerie, a corrupted protein known as the prion, which causes the brain-eating disease known as kuru and mad cow.

Obviously, no one could approach this countertop in anything less than a full positive pressure personnel suit, those frightful outfits which envelope their wearers in their own world, walking ad hoc atmospheres that populate our nightmares. But even this dreaded assortment can be killed—or, in the prion’s case, weakened and made vulnerable—with something you probably have under the kitchen sink: sodium hypochlorite, or bleach. When mixed with water, bleach is among the most effective disinfectants known.

Pioneered as a disinfectant by French chemists in the Victorian era, the mechanism by which it kills was a mystery until 2008, but the killer in your cabinet has helped shape sanitation and public health around the world.


Bleach kills by striking at the pathogen’s very nature.

“A key effect of bleach is that it acts as a denaturing agent,” said Dr. John Lynch, associate professor of hospital epidemiology at Harborview Medical Center and the University of Washington. “It basically attacks proteins and causes them to unfold and glom together.”

Think about what happens to an egg, as it goes from liquid to solid while being cooked. As the proteins denature and clump together, Lynch said, the pathogens basically cease to exist as anything resembling a functional organism.

Despite bleach having been used in the capacity for hundreds of years, it was only in 2008 when a research team at the University of Michigan, under the guidance of molecular biologist Ursula Jakob, discovered the denaturing process. The scientists observed how the substance killed by studying bleach’s main active ingredient, hypochlorite.

Sodium hypochlorite was first recognized for its pathogen-slaying properties in the early 1800s. Swedish chemist Carl Wilhelm Scheele discovered chlorine in 1774, and French chemist Claude Berthollet first made sodium hypochlorite—then called Eau de Jeval, or Jeval water, after the town where it was produced—in the 1780s, although he used it primarily as a whitening agent for fabrics. Another French chemist, Antoine-Germaine Labarraque, was the first to recognize the solution’s disinfecting properties. By 1823, the Paris police were using bleach to disinfect corpses and latrines.

Bleach is a thorough destroyer. It does not leave living genes in its wake.

Today, the same bleach that can be found in your home is used as a standard mid-level disinfectant in hospitals, labs and other facilities around the world. According to the Clorox company’s website, Annie Murray, an investor in the original company and a grocer in Oakland, helped popularize the domestic use of bleach in 1916 by pushing for a less-concentrated solution and giving away samples at her store, talking up its cleaning and germicidal properties.

Bleach resistance is primarily mechanical; as it must come into contact with the microorganisms to kill them. If dirt and grime—or a protective layer of bacteria known as a biofilm—cover the targeted pathogen, it may not be exposed to enough bleach to destroy it. While Jakob’s team discovered that bacteria release a protein chaperone called Hsp33 to help mitigate bleach’s effects, pathogens do not develop a resistance to bleach in the same way they do antibiotics.

So-called superbugs acquire new genes—or ramp up the production of already resistant ones—to become resistant to specific drug classes. But bleach is a thorough destroyer. It does not leave living genes in its wake.

“Bleach is a super-class agent,” said Lynch. “It just impacts all proteins. The key thing is it has to get to the proteins.”

Commercially available bleach products effectively reduce the pathogen load in most household situations. Relatively fragile viruses like influenza are easily killed by bleach; in fact, soap and water or even alcohol can get the job done. Norovirus, the winter vomiting bug, is considerably tougher, but it, too will denature if exposed to bleach.

The ready availability of such a versatile and effective disinfecting agent in Global North countries has a key impact on public health. Faced with an epidemic of Hepatitis A among homeless populations without access to basic sanitation and hygiene products, San Diego hosed its streets down with bleach.

“The popularity of bleach was initially due to the abundance and low cost of the resources needed to manufacture it: brine and electricity,” Dr. Preston J. MacDoughall, a professor in the department of chemistry at Middle Tennessee State University, said via email. Electricity’s abundance in the 1800s, combined with good marketing and the removal from the U.S. market of dominant German chemical concerns in World War I, all perhaps contributed to the product’s ubiquity now, a commonness that belies its importance.  

“Basic sanitation and hygiene is probably one of the most important drivers of human health,” Lynch said. “Our access to things like bleach, soap and water, and clean water is one of the most important things that have improved longevity and overall health in the Global North and other developed countries.”

Diseases that have plagued society since recorded time can now be effectively contained—their very essence unspooled and made a useless tangle like headphones pulled from a pocket—by a killer in your cabinet.

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