The science · Mechanism
How hypochlorous attacks microbes
Hypochlorous does not depend on a single weak point. In laboratory studies it reacts within milliseconds with the sulphur-containing parts of proteins and, at the same time, shuts down the systems a microbe needs to make energy, take in nutrients and copy its DNA.[1][3][4][5][6]
This page explains how hypochlorous works in principle, mostly from laboratory research on bacteria. It does not describe the performance of any EQ8 product. For that, see the EN standards each product is certified to.
In one paragraph
Hypochlorous reacts within milliseconds with the sulphur-containing parts of proteins, so a microbe’s essential proteins unfold and clump.[1][3] At the same time it destroys the iron-containing systems the cell uses to make energy, stops the pumps that bring in nutrients and inhibits DNA copying.[4][5][6] Because so many vital systems fail at once, bacteria have little chance to adapt.[7] Viruses are inactivated through damage to the proteins they need to infect cells or to their genetic material, depending on the virus.[8][9] Spores are better protected and need longer contact, which is why each kind of microbe is tested to its own standard.[10][11]
Where it comes from
Where hypochlorous comes from in the body, step by step
Hypochlorous is not an invention of the laboratory. White blood cells make it to destroy the microbes they capture. Here is how, one step at a time.
The body’s security service
Your blood carries red blood cells, which transport oxygen, and white blood cells, which defend you. Neutrophils are the most numerous white blood cells in the blood.[14]
The first responders
When microbes get in, for example through a scratch, neutrophils are the first immune cells to reach the spot, before the rest of the immune system has organised itself.[14]
Swallowing the microbe
A neutrophil wraps itself around a bacterium and pulls it inside. The microbe ends up sealed in a small bubble inside the cell, called a phagosome, like an intruder locked in a sealed room. This is where most microbes are killed and digested.[15]
Making a disinfectant in the sealed room
To kill what it has trapped, the neutrophil makes hypochlorous on the spot, from two ingredients and one tool.[15]
- Hydrogen peroxide. The neutrophil makes this itself, in a sudden burst, using an enzyme complex that assembles on the wall of the bubble. On its own, hydrogen peroxide is a far weaker germ-killer.[14][7]
- Chloride. The chloride from salt, dissolved throughout the body’s fluids at much higher levels than similar ions.[7]
- Myeloperoxidase, the tool. An enzyme is a natural machine made of protein that makes one specific chemical reaction happen quickly. Myeloperoxidase combines hydrogen peroxide and chloride into hypochlorous, and it makes up about 5% of a neutrophil’s dry mass.[14][15]
How the body limits the damage
Because hypochlorous is made inside the sealed bubble and reacts so quickly, it is largely spent there, where it also forms gentler, longer-lived chloramines.[14] Outside the bubble, blood proteins such as albumin and the cells’ own glutathione mop up any that escapes.[14] When that control fails, as in long-lasting inflammation, hypochlorous can also damage the body’s own tissues.[14]
At a glance
Five things happen at once
Inside a bacterium
Explore the targets
A cross-section through the edge of a bacterium, drawn the way biology textbooks draw it. Choose a target to zoom in and see how it normally works, then add hypochlorous to see what it does.
The whole cell edge
Explore the targets
Five targets, each where it sits in a real bacterium. Choose one to zoom in.
1 · Speed
Why “milliseconds” is accurate
Chemists measure how fast two molecules react with a rate constant: the higher the number, the faster the reaction. At pH 7.4, hypochlorous reacts with cysteine, one of the two sulphur-containing building blocks of proteins, at 3.6 × 10⁸ per molar per second, and with methionine, the other, at 3.4 × 10⁷.[1] These are among the fastest reactions measured for protein building blocks.[1][2] Sulphur-containing compounds react about a hundred times faster with hypochlorous than any other part of the cell, and in laboratory studies lethal damage to bacteria occurs within a tenth of a second of exposure.[7]
It reacts next with the nitrogen-containing groups of proteins, forming chloramines. These are milder oxidants, many with antimicrobial activity of their own, but they are 10,000 to 100,000 times less reactive than hypochlorous and act mainly on the same sulphur-containing sites.[7]
Each step on the scale is ten times faster.
2 · Proteins
Unfolding and clumping
Proteins only work when they are folded into precise three-dimensional shapes. A 2008 study in the journal Cell showed that small amounts of hypochlorous, relative to the amount of protein, make proteins unfold in the test tube and make heat-sensitive proteins inside bacteria clump together irreversibly.[3]
The researchers concluded that the antimicrobial effect of bleach rests largely on this clumping of essential bacterial proteins. They compared it with heat: like the proteins in a cooked egg, the bacterial proteins lose their structure and stick together, but the cause is chemical rather than thermal.[3]
3 · Energy
Switching off the power supply
A bacterium makes its energy through a chain of proteins in its membrane, many of which contain iron. In 1981, researchers found that hypochlorous rapidly and irreversibly oxidises these cytochromes, the cell’s adenine nucleotides (which include ATP, its energy currency) and its carotene pigments.[4]
In a common laboratory bacterium, Escherichia coli, the oxidation of the cytochromes coincided with the loss of respiration. The authors concluded that killing results mainly from the loss of energy production, through destruction of the cell’s electron transport chains and its adenine nucleotide pool.[4]
4 · Transport
Locked out of nutrients, not burst open
A 1986 study found that hypochlorous reduces the ability of bacteria to take up amino acids and sugars, and that this loss of transport roughly coincides with the loss of viability.[5]
The researchers located the attack at the cell envelope, but found that the cells do not die because their membrane loses its structure. The membrane stays physically intact; it is the protein “doors and pumps” in it that stop working. Claims that hypochlorous kills by rupturing cell walls are not supported by this research.[5]
5 · DNA
Stopping the microbe from multiplying
The myeloperoxidase–hydrogen peroxide–chloride system, which is how white blood cells make hypochlorous, strongly inhibits DNA synthesis in bacteria, an effect also seen with hypochlorous itself.[6][14] The researchers point to the cell envelope and the machinery that starts DNA copying as the likely targets.[6] In bacteria, DNA copying starts at a site attached to the inner membrane, and the loss of DNA copying follows the loss of that attachment at doses that closely match those that kill.[7]
6 · Many targets
Why the attack is so hard to survive
Proteins, energy production, transport and DNA copying are all hit at the same time. Bacteria do have defences: small sulphur-containing molecules such as glutathione that mop up reactive chlorine, repair enzymes, and regulators that switch on protective genes.[7] The chaperone Hsp33, a protein that protects other proteins, shields essential proteins from clumping and raises tolerance to hypochlorous.[3]
These defences raise tolerance a little. Because so many vital systems fail together, adaptation is difficult, though not impossible. Researchers also note that exactly how reactive chlorine kills is still not fully defined and probably varies between species and conditions.[7]
7 · Viruses
It depends on the virus
Viruses are not living cells, so “killing” here means stopping them from infecting. With one well-studied virus, free chlorine caused little or no loss of the virus’s genetic function compared with its loss of infectivity, pointing to damage to the protein coat the virus needs to attach to and enter cells.[8]
With other viruses, chlorine also damages the genetic material, and in a study of three closely related viruses the same disinfectant acted in different ways.[9] Mechanism alone therefore cannot tell you how a product performs against viruses;[9] that is what the virucidal standard EN 14476 tests.
8 · Spores
Armour and a hidden target
Bacterial spores are dormant, heavily protected forms of some bacteria. Spores with their outer coat removed, or with a faulty coat, are killed much faster by hypochlorite, so the coat is a major protective factor.[10][11]
The killing does not appear to work by damaging the spore’s DNA. The evidence points instead to damage to the spore’s inner membrane.[11] Because the oxidant first has to get through the coat, spores need longer contact or higher strength,[10] which is why sporicidal activity has its own standard, EN 17126.
9 · Yeasts and moulds
Tested, not assumed
This page does not draw on mechanistic studies in yeasts and moulds. For activity against yeasts, the EQ8 DEFEND products rely on the yeasticidal test, EN 13624, rather than on mechanism.
10 · In use
Why surfaces should be clean, and why it does not linger
Hypochlorous is small and uncharged, so it passes into microbes easily, while the charged hypochlorite form stays largely outside the cell. This is why pH, which decides the balance between the two forms, is part of how it works.[12]
Hypochlorous is used up as it reacts. Organic matter such as dirt, manure and bedding consumes it before it reaches the microbes, which is why surfaces should be cleaned first.[12] Once released, it breaks down in light to chloride and oxygen, with an estimated half-life of 1 to 4 hours, and it does not build up in living things.[13]
What this page does not cover. EQ8 products are for hands and for inanimate surfaces and equipment, as directed on their labels. This page does not describe use in or near the eyes, mouth, nose or ears, use as a fog or mist, or use on wounds.
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