The journey of Kathon kicked off in the 1970s, tracing roots to the urgent need for better preservation in water-based products. Microbial growth in paints, adhesives, and personal care products caused headaches for manufacturers, with spoilage leading to waste and safety issues. Researchers at Rohm and Haas zeroed in on isothiazolinone compounds for their broad-spectrum microbial control. Kathon’s blend of methylisothiazolinone (MIT) and chloromethylisothiazolinone (CMIT) quickly outperformed older preservatives like formaldehyde donors, offering power at low concentrations and fewer unwanted effects in final products. Over the next few decades, global industry and regulators kept pushing for less toxic, more stable alternatives, yet Kathon’s formula kept its place thanks to strong antimicrobial activity and its compatibility with various product formulations.
Kathon contains two main active chemical components: methylisothiazolinone and chloromethylisothiazolinone. This duo attacks a broad range of bacteria, fungi, and yeasts. What makes Kathon stand out comes down to its balance: enough power to break down tough microbes, but at concentrations so low that many applications can keep formulas clear and stable. It comes as a transparent to pale yellow liquid with a faint, sharp odor noticeable to folks working with the raw material. Kathon exists in many blends and concentrations—0.0015% to 0.1%—with fluid presentation engineered for different industrial and consumer uses.
Kathon presents as a water-soluble, low-viscosity fluid with a density of around 1.02 g/cm³ at room temperature, making it easy to mix in manufacturing. Stable between pH 4 and 8, the active isothiazolinones degrade quickly outside these limits or under strong UV light. That property matters for environmental impact, as it curbs long-term buildup in wastewater, but also means careful storage is necessary in factories. These compounds sit at the core of Kathon’s effectiveness—disrupting enzyme and membrane systems in microbes, but also imposing strict handling requirements to prevent accidental activation in storage.
Kathon bears clear technical guidelines: typical commercial products mark CMIT/MIT at 1.5% (like Kathon CG/ICP) or other ratios depending on target use. Labels on drums or containers from major suppliers carry hazard warnings due to potential skin and eye irritation, aquatic toxicity, and sometimes specific national regulatory symbols. The product's SDS outlines risks and PPE recommendations such as chemical gloves and goggles. Each batch includes info on pH, color, assay range, and specific gravity. Facilities track batch numbers for traceability since industry and regulators want to tie any complaint or harm back to the sources—a real-world demand, not just a checkbox.
Manufacturers rely on a two-step process. Starting from methylthio compounds, oxidation produces the isothiazolinone ring structure. Careful control of temperature, oxidants, and timing is vital since side reactions cut into purity and yield. Small tweaks—adjusting chlorine concentration, temperature, or pH—shift production away from unwanted byproducts like sulfonates or dimers. After separation, blending and dilution create the sold product, stabilized by magnesium nitrate or magnesium chloride salts. These carrier salts matter for shelf life, regulatory approval, and direct impact on finished applications.
The real magic happens in the chemical backbone. Kathon’s active isothiazolinones react with sulfur-containing amino acids in microbial enzymes—disrupting metabolic pathways and quickly stopping cell growth. Modifications over the years explored fluorine or bromine substitutions, hoping for more focused biocidal activity or lower toxicity, but most efforts came with trade-offs: lower effectiveness or new safety problems. Oxidation or hydrolysis reactions remain a chief concern for storage and use since these degrade the active compounds. Engineers depend on antioxidants or stabilizers, not only to extend shelf stability but to avoid chemical burns or unforeseen product failures on customer shelves.
Kathon appears in product guides under names like Euxyl K 100, BIOBAN, Proxel, Neolone, and Preventol. Synonyms in the literature and regulatory filings include 5-chloro-2-methyl-3(2H)-isothiazolone, 2-methyl-4-isothiazolin-3-one, or CMIT/MIT mixture. Each supplier uses its own branding or minor formulation twists, resulting in widespread use under different labels in paints, adhesives, cutting fluids, and personal care items. Checking the actual percentage of CMIT/MIT always makes sense, since concentrations can vary—especially in bulk blends for industrial vs. cosmetic markets.
Safety for Kathon draws strong attention. Even though Kathon handles a mighty microbial punch, its potential to trigger skin and eye irritation—or trigger allergic contact dermatitis—means regulatory controls are non-negotiable. Factories use closed mixing systems with ventilated hoods, and workers wear gloves and eye protection, not only to meet compliance but to protect real people on the floor. Most countries set maximum use limits for various categories, like 15 ppm in rinse-off cosmetics in the EU, and ban the blend in leave-on skincare. Industry trains for emergency eye-washing and quick spill containment; accidental exposure often leads to strict incident reports and sometimes medical review. Improper use in humidifier disinfectants in South Korea led to thousands of injuries and deaths, showing what real-world harm follows from careless application and poor oversight.
You find Kathon in a laundry list of products: paints, adhesives, paper coatings, metalworking fluids, detergents, and personal care items like shampoos and conditioners. Its low-dose effectiveness appeals to manufacturers looking for reliable protection without altering a product’s aroma, feel, or look. Tough industrial situations—like cooling towers or oil extraction rigs—depend on Kathon for long-term microbial protection to keep equipment clean and free of fouling. In everyday use, consumers come in contact with tiny concentrations in cleaning products or household cleaners, often unaware unless allergies prompt a label check. Restrictions in the EU and other markets now limit its use in leave-on skin and hair products, pushing companies to switch preservatives for higher risk groups.
Recent research for Kathon continues to focus on safer use and finding alternatives. Studies examine how Kathon interacts with skin proteins, testing formulas to minimize irritation or allergenic potential. Analytical labs use advanced chromatography and mass spectrometry to spot Kathon in finished products and wastewater, crucial for enforcing product recalls or pollution controls. Industry-sponsored trials compare Kathon with newer, “greener” biocides, sometimes leading to slight tweaks in proportions or new blends with other antifungals. Regulatory science teams pour over health and environmental data, trying to set safer exposure levels while keeping products protected. The need for rapid detection in the field—a technician running a quick test at a food plant or factory—drives development for test strips or sensors, making it easier to manage exposure in the real world.
Kathon’s toxicity sits under a microscope. Low doses have proven safe for most people, which led to its approval in many everyday items, but even small exposures can spark allergic reactions in sensitive users. Dermatologists report Kathon as one of the leading triggers for contact dermatitis, especially as regulations tighten on other preservatives. Animal studies link high levels to irritation or organ effects, though most consumer products hold less than 0.01% active. In wastewater, Kathon degrades fairly fast in sunlight and oxygen-rich conditions—but it harbors acute toxicity for fish and aquatic invertebrates, pushing regulators to demand careful discharge management. Incidents in humidifier solutions—where doses ran far too high—showed tragic failures in risk management, and motivated tighter oversight. Factories and suppliers now publish extensive toxicology data and review findings with global authorities, aiming to keep pace with both science and public scrutiny.
Kathon’s future hinges on health, environment, and innovation. Consumer push-back against synthetic preservatives, rising rates of allergic reactions, and legal hurdles on both sides of the Atlantic force companies to explore new solutions or substitute blends. Cost remains a driver, since Kathon covers big industrial territory without adding much to the bottom line. Changes in climate and more recycled water in industry bring new microbial challenges, keeping biocide demand high but upping the bar for safety and traceability. Process chemistry research explores less toxic isothiazolinone variants or biodegradable alternatives with the same robust performance, but so far, Kathon keeps beating challengers for certain tough jobs. Next-generation product designers aim to use less, combine with physical barriers, and train workers on real risks—not just paperwork. Kathon’s story grows with changes in formulation science, regulatory oversight, and the never-ending battle against bugs in our products and infrastructure.
Ever wonder why shampoos, lotions, or even paints stay fresh long after you open the bottle? Usually, it’s because of something like Kathon. This chemical blend, made from methylisothiazolinone and methylchloroisothiazolinone, keeps all sorts of products from turning into a science experiment full of mold and bacteria. I’ve spent years reading the ingredient lists on bottles in my own bathroom, and Kathon comes up more often than you’d expect.
Growers, painters, and folks in cleaning industries understand how a little bit of contamination makes products go bad. In paints, water-based cleaners, adhesives, and laundry detergents, Kathon gets mixed in to stop bacteria and fungi from growing. Factories risk huge losses without good preservatives. I’ve seen paint shops lose entire batches to spoilage because a preservative ran low. With Kathon, the shelf life stretches, and product recalls drop.
People are starting to worry about what goes into the products they use every day, and for good reason. Kathon comes with baggage. Skin allergies aren't rare. Dermatologists report more folks with contact dermatitis tied to these chemicals. A run-in with a harsh preservative teaches you to read future labels a lot more carefully. I once tried a “hypoallergenic” lotion that gave me a rash, only to learn later it contained a Kathon blend.
Europe and Canada set limits on how much Kathon companies can put in personal care goods. In the United States, the Food and Drug Administration and Environmental Protection Agency keep an eye on how these chemicals are used, but labeling relies mostly on self-reporting. Studies show low levels cause fewer problems for most people, but reactions can happen with repeated exposure. No one wants a cleanser or lotion to turn against them.
Mold and bacteria don’t need much of a window to ruin something people count on. Kathon works well because it’s effective at low concentrations. Fewer preservatives mean bigger chance for spoilage. For small companies or anyone bottling bulk amounts, tossing out a spoiled batch hurts. From what I’ve seen, most companies want to stay on the safe side of public health and business risk, so they keep using proven options like Kathon.
Switching away from Kathon brings headaches. Alternatives exist, but they can be pricier or break down sooner, making products less appealing or safe to use. Some alternatives deliver milder reactions, but they don’t always match the shelf life or reliability. Any swap needs to consider cost, public health, and the environmental impact. Given the increase in awareness, I see companies experimenting with safer blends of preservatives, even if it costs a little more.
People want safe, reliable products with fewer chemicals linked to allergies. I’ve learned it helps to stay aware of product recalls, talk to a doctor if you suspect a reaction, and pick items with ingredient lists you understand. Regulators, scientists, and companies push for better research and safer formulas. That’s changing the market, but for now, Kathon remains common in many home and work goods. Thinking about health and safety, it’s clear that finding new ways to limit exposure while keeping products stable is the challenge ahead.
Kathon carries the job of preserving products. You’ll find it in hand soaps, shampoos, laundry detergents, and even wet wipes. It fights off bacteria and mold, so stuff lasts longer on the shelf and doesn’t turn into a science project after a few weeks.
The main ingredients in Kathon are methylisothiazolinone (MI) and methylchloroisothiazolinone (MCI). These chemicals work well against microbes and keep products fresh. You’ll see them on ingredient lists, though sometimes in tiny font you need a magnifying glass to read.
Plenty of folks with jobs in cleaning, healthcare, or hairdressing end up touching Kathon often. Dermatologists started noticing more people with itchy, red skin on their hands, necks, or even faces. European studies saw a spike in cases of allergic contact dermatitis from products that used Kathon. This kind of allergy forms after enough exposure. At first, you use a new face wash or lotion — everything is fine. Maybe a few weeks or months later, you break out with a stinging rash you can’t blame on stress or diet. Even low doses can do this once your skin has learned to recognize Kathon as a threat.
Shampoo and cleaning wipes don’t pose an immediate risk to everyone. Some people can use them daily with no trouble. But for those who react, the symptoms aren’t subtle. In my own family, someone worked with cleaning agents for years and had reliable, rugged skin — until using new soaps and wipes. Angry, dry patches popped up. Only after removing anything with Kathon did skin finally heal.
Regulators pay attention when too many rashes show up linked to one preservative. The European Union cut back on how much Kathon companies could use in leave-on products. They banned its use in products like creams that stay on skin, making sure only rinse-off items use it and at lower concentrations. In the US and Canada, rules are less strict, but dermatologists there also warn people with sensitive skin or known allergies to check ingredient lists closely.
People trust body wash and wipes to be gentle, but full transparency still lags. Labels often bury Kathon’s full name or use strings of chemical terms that most people gloss over. Healthcare advisors and advocacy groups recommend companies make it easier to spot possible triggers.
Switching preservatives isn’t simple for companies. Kathon keeps products shelf-stable without costing too much. Short-term, people can opt for “fragrance-free” or “hypoallergenic” items, though those don’t guarantee Kathon’s absence. Reading every label and looking for MI and MCI makes a difference.
Companies can help by rethinking formulas—using older preservatives like parabens, which actually cause fewer allergies in many people, or turning to entirely new options that don’t rely on isothiazolinones. Doctors play a big part, too. Patch tests can zero in on reactions and help guide patients to safer everyday choices.
Nobody wants an allergy from soap or lotion. Large numbers of dermatitis cases tell us that Kathon, while useful as a preservative, isn’t always the safest option for everyone’s skin. Every shopper has the right to know what touches their skin and to pick products that keep them comfortable — and rash-free.
Kathon stands out in the world of preservatives. Anyone who has worked with paints, cosmetics, or personal care items likely recognizes the need to keep bacteria and mold at bay. That’s where Kathon steps in. It isn’t just chemistry for the sake of shelf-life—there are real substances doing the heavy lifting inside this product.
The powerhouse behind Kathon is a mix of two main substances: Methylchloroisothiazolinone and Methylisothiazolinone. If you’ve ever looked at labels on shampoo, dish soap, or household cleaners, you might have noticed these tongue-twisters listed in the fine print. In technical circles, people often shorten them to MCI and MI.
Each ingredient serves a distinct purpose. MCI and MI go to work by disrupting the cells of bacteria, fungi, and yeast. That means fewer headaches for anyone trying to manage spoilage in their products. This combination packs a real punch, needing only tiny amounts—usually less than one percent of the product—to keep unwanted growth out. Smaller doses mean less risk for users, as high concentrations of chemical preservatives often lead to allergic reactions or skin irritations.
I learned firsthand about the practical side of preservatives in a family-owned paint shop. Each bucket sitting on a shelf in the back room had a story. On warm, humid days, any product without robust protection spoiled fast. You could smell the change. It’s surprising how quickly mold can take over, turning hard work into a waste of time and money. Kathon’s mix of MCI and MI made a real difference; the paint lasted longer, looked better, and kept customers happy. People didn’t want to repaint or throw away spoiled batches. They wanted reliability.
Of course, even strong preservatives have limits. Some folks are sensitive to MCI and MI. Reports of skin allergies—especially in Europe—pushed manufacturers to rethink how much of these ingredients should go into personal care products. In response to customer concerns and evolving regulations, many companies dropped or adjusted the levels of these chemicals in leave-on applications like creams and lotions.
Tough decisions follow when products offer real benefits but spark health debates. In my experience, businesses benefit by being upfront with customers and regulators. Labeling isn’t just a legal formality; it’s a way to build trust. People want to know what they’re using. Scientists, advocates, and everyday users now keep a close eye on preservatives and other additives.
No single answer fits every need. Some manufacturers switched to alternative preservatives—like sodium benzoate or organic acid blends—in response to demand for gentler options. Still, MCI and MI aren’t going away. They keep working quietly in many industrial and household products, favored for their efficiency at low concentrations. Companies who want to maintain trust should invest in regular safety reviews, field honest conversations with consumers, and stay open to new science. Well-informed choices beat knee-jerk bans or quiet cover-ups every time.
Kathon shows up in all sorts of places you probably wouldn’t expect. It preserves shampoos, hand soaps, household cleaners, and even some paints. As a preservative, it fights off bacteria and mold, which keeps products fresh longer. But those tiny drops of Kathon can pack a punch that hits some people a lot harder than others.
Over the past few years, allergy cases related to Kathon have really spiked. The technical name is “methylisothiazolinone/methylchloroisothiazolinone” (often labeled as MI/MCI). Dermatologists raised the alarm after seeing patients with itchy rashes or red, burning skin—especially after using “mild” or “hypoallergenic” products. A 2017 study published in the journal Contact Dermatitis found that allergy rates to MI soared from under 2% in the early 2000s to nearly 11% among tested patients just a decade later. That’s not some tiny blip. It’s more people getting burned by an ingredient that isn’t always up front on the label.
Living with skin allergies, I can say shopping for basics like soap or lotion means pulling out my phone and double-checking ingredients for anything suspicious. The first time I reacted to Kathon, my hands felt raw for days after using a “gentle” dish soap. It taught me Kathon allergies don’t just happen to people with overly sensitive skin or folks with medical backgrounds. They hit regular people who just want to wash up without having to worry about rashes or hives.
Regulators saw the numbers and started making changes. The European Union slashed the maximum amount Kathon allowed in cosmetics and banned it outright in products left on the skin, like lotions or baby wipes. In the United States, rules aren’t as strict, and Kathon can turn up in plenty of products—sometimes hiding behind chemical names many shoppers don’t recognize. That gap between regulations in different countries puts American shoppers at higher risk, especially those who don’t know what to watch for in the fine print.
Better labeling matters. Big brands tweak formulas or advertise “MI-free” products, and apps help decode ingredient lists. But that doesn’t mean everyone has access or time to check every bottle, especially people dealing with budget constraints or language barriers. The solution can’t fall entirely on shoppers learning chemistry. Companies should feel real pressure from both sides—customers and regulators—to go beyond the bare minimum with transparency and safer alternatives.
There’s no shortage of alternatives to Kathon. Some brands use sodium benzoate, potassium sorbate, or even certified organic methods to extend shelf-life. Products with simpler formulas and transparent labeling actually exist; they just need to be easier for everyone to find. If folks had better access to these options, fewer people would wind up sitting in a doctor’s office with a mysterious rash—only to find out their new soap was the culprit.
We can’t count on everyone to become an expert on preservatives or spot every chemical variation. Wiser regulation levels the playing field so shoppers don’t have to become detectives every time they hit the store. Allergy cases linked to Kathon show what happens when safety testing, clear language, and real accountability lag behind the science.
Kathon has earned a reputation as a strong, fast-acting preservative. Many folks working in paints, cooling towers, and cosmetics depend on it for stopping bacteria, fungi, and algae. This power comes with real responsibility. Safe storage and careful handling make the difference between a workday that ends on time and one that ends in the ER—or worse. Years in industrial facilities and labs have given me a healthy respect for chemicals with this much punch.
Hydrated eyes, intact lungs, and skin without burns matter more than meeting a quarterly target. I remember pulling a drum of Kathon from a forgotten corner of a maintenance shed—its original label peeling, its cap crusted. More than once I’ve seen containers like that spill. Proper storage isn’t just a compliance line on a form. It’s about buying sturdy, chemical-resistant drums with airtight seals and never allowing Kathon to sit near sunlight or heat vents. The stuff needs to stay cool and out of reach of untrained hands. I once watched an airflow from a heat pump send vapor back toward a technician; it drove home the need for smart placement far from air intakes. Even letting Kathon freeze impacts its stability, which means product failures and downtime.
Kathon can burn skin, irritate eyes, and cause lung damage. I always double-check that everyone has nitrile gloves, goggles, and a face shield before we crack open new barrels. Clothes with solid sleeves and pants build an extra barrier against spills. Anyone using this stuff without training risks more than just a ruined uniform. Years ago, I flinched as a too-casual tech wiped sweat on her brow after opening a container; within minutes, her red skin showed what shortcuts can cost. Respirators make sense in any setting with venting issues, not just high-volume tanks. Never underestimate a small splash—a dribble joining sweat can outpace any shower station if people don’t move fast.
Rooms set up for proper air exchange keep workers safer. Trying to slap a fan in an open window is not enough. Local exhaust systems matter in labs and plant settings where Kathon gets weighed or transferred. Good warning labels, including hazard icons and date logs, cut confusion when emergencies hit. A clear, durable label stops the guesswork during audits, spills, or product swaps. Skipping this step because “everyone knows” what’s in a drum only leads to accidents. I once found a bottle with faded marker scribbles, sitting next to cleaning fluid—the risk of confusion could have turned an ordinary day into a hazmat call.
No matter how careful a team acts, spills happen. Having a plan, the right absorbent socks, and neutralizing agents close at hand means less panic and faster cleanup. Spent materials shouldn’t go down a standard drain—hazardous waste runs need explicit paperwork. Training drills, eye-wash stations, and easily found exit routes make all the difference during those rattling moments that test any crew. After all, a safe end to the shift means no stories told to the EMTs or insurance adjusters.
Kathon saves companies money on spoilage and keeps systems clean. No one enjoys downtime or recalls. Still, shortcuts tempt busy teams. Trusting training, sharing real stories about accidents, and keeping clear rules about handling reinforce a culture where people watch each other’s backs. Being safe around Kathon becomes second nature—not an extra chore. In my experience, quiet attention during storage and handling has kept my teams healthy, productive, and coming back to work the next day with all ten fingers and their good names intact.
| Names | |
| Preferred IUPAC name | 5-chloro-2-methyl-2H-isothiazol-3-one; 2-methyl-2H-isothiazol-3-one |
| Pronunciation | /ˈkæθɒn/ |
| Identifiers | |
| CAS Number | 55965-84-9 |
| Beilstein Reference | 2631340 |
| ChEBI | CHEBI:74943 |
| ChEMBL | CHEMBL4296751 |
| ChemSpider | 204801 |
| DrugBank | DB14095 |
| ECHA InfoCard | 03f206e4-015a-455d-8402-bbfe28286abc |
| EC Number | 55965-84-9 |
| Gmelin Reference | 353301 |
| KEGG | C18613 |
| MeSH | D005704 |
| PubChem CID | 24866049 |
| RTECS number | GZ1250000 |
| UNII | 6KGM82RM3P |
| UN number | UN 3082 |
| CompTox Dashboard (EPA) | DTXSID0029275 |
| Properties | |
| Chemical formula | C8H9Cl2NO2S |
| Molar mass | 394.9 g/mol |
| Appearance | Clear, light yellow to yellow liquid |
| Odor | Mild medicinal |
| Density | 1.03 g/cm³ |
| Solubility in water | soluble |
| log P | -0.24 |
| Vapor pressure | <10 mm Hg @ 20°C |
| Acidity (pKa) | 2.7 |
| Basicity (pKb) | 10.3 |
| Magnetic susceptibility (χ) | 0.97 × 10⁻⁶ |
| Refractive index (nD) | 1.410 |
| Viscosity | 20-80 mPa.s |
| Dipole moment | 1.87 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | Kathon does not have a published standard molar entropy (S⦵298) value. |
| Pharmacology | |
| ATC code | D08AJ57 |
| Hazards | |
| Main hazards | Causes severe skin burns and eye damage. May cause an allergic skin reaction. Toxic to aquatic life with long lasting effects. |
| GHS labelling | GHS05, GHS07, GHS08 |
| Pictograms | GHS05,GHS07,GHS09 |
| Signal word | Warning |
| Hazard statements | H302, H315, H318, H334, H317, H400, H410 |
| Precautionary statements | P264, P280, P302+P352, P305+P351+P338, P310, P333+P313, P362+P364, P501 |
| NFPA 704 (fire diamond) | Health: 3, Flammability: 1, Instability: 1, Special: - |
| Flash point | Flash point: >100°C (>212°F) |
| Autoignition temperature | 199°C |
| Lethal dose or concentration | LD₅₀ (oral, rat): 333 mg/kg |
| LD50 (median dose) | LD50 (median dose): 1,020 mg/kg (rat, oral) |
| NIOSH | TQ6300000 |
| PEL (Permissible) | No PEL established. |
| REL (Recommended) | 0.1 mg/m³ |
| IDLH (Immediate danger) | IDLH not established |
