Is Benzisothiazolinone Safe? A Simple Answer You Can Trust

No, I do not consider Benzisothiazolinone safe for the skin. Europe’s safety panel reviewed it and refused to clear it in cosmetic use classifying it as moderate skin sensitizer. In one report, 20 parts per million in a glove was enough to sensitize people. It’s not on the EU list of permitted cosmetic preservatives, though the United States still allows it. I rate it Not a Fan.

Regulators split sharply on Benzisothiazolinone. The cosmetic industry asked Europe to allow 100 parts per million, or 0.01%, and was refused. Europe tightened its hazard rules in 2025 instead. Any product containing 0.036% or more must now be labeled as a skin sensitizer, down from the old 0.05% threshold. The United States sets no limit on Benzisothiazolinone for cosmetics at all, and Canada sets none either.

Below, you’ll see why the panel agreed that the Benzisothiazolinone amount reaching your body is harmless yet still refused to approve it. You’ll also learn whether it’s the same as Methylisothiazolinone, and why it turns up in laundry detergent.

What Is Benzisothiazolinone?

Benzisothiazolinone is a synthetic preservative and industrial biocide. Chemists shorten it to BIT, and it belongs to a family called the isothiazolinones. It kills bacteria, mold, and yeast in water-based products. Its main home is industry rather than the bathroom cabinet.

What Does Benzisothiazolinone Do In Cosmetics?

Benzisothiazolinone stops microbes from growing in anything that contains water. That job matters, since a contaminated product can cause real harm. In practice, though, most of its use sits outside cosmetics.

You’ll find Benzisothiazolinone most often in:

• laundry detergents and fabric softeners
• dish soaps and household cleaners
• paints, stains, and adhesives
• water-based industrial fluids
• some US personal care products, mainly rinse-off

Benzisothiazolinone is not a food ingredient. It carries no E-number and appears only in cosmetics, cleaning products, and industrial goods.

How Is Benzisothiazolinone Made?

Benzisothiazolinone is fully synthetic, built in a lab rather than drawn from a plant. The public databases give no published manufacturing route, so its precursors stay unlisted. The safety dossier does name two impurities left in the finished ingredient: 5-chloro-1,2-benzisothiazolin-3(2H)-one at up to 0.22%, and 2,2-dichlorobisbenzamide below 0.1%. Even so, the main concern here is the ingredient itself, not its residues.

Does Benzisothiazolinone Penetrate The Skin?

Yes, Benzisothiazolinone penetrates the skin, which was measured in human skin rather than guessed. In a lab study on donated human skin, about 26% of an applied dose passed through. Its size explains why.

Benzisothiazolinone weighs only 151 daltons, far below the roughly 500-dalton point where skin starts blocking molecules. It’s also moderately oil-loving, with a LogP near 1.3, so the skin barrier does little to stop it.

Here is the part that surprises people. Systemic absorption of Benzisothiazolinone is not the problem, because the amount reaching your bloodstream stays small. The trouble happens at the skin itself, where this molecule teaches your immune system to react.

What Is Benzisothiazolinone Called On Labels?

Manufacturers list Benzisothiazolinone under several names:

• Benzisothiazolinone
• 1,2-Benzisothiazol-3(2H)-one
• 1,2-Benzisothiazolin-3-one
• BIT

On cosmetics, the label uses the short INCI name, Benzisothiazolinone. On a cleaning product, you are more likely to meet its formal chemical name, 1,2-benzisothiazol-3(2H)-one, often paired with its CAS number 2634-33-5. Cleaning products did not always list their ingredients. California has been requiring disclosure since 2021, so most national brands now publish a full list on the label or their website.

Does The U.S. FDA Restrict Benzisothiazolinone In Food And Cosmetics?

No. The FDA sets no limit on Benzisothiazolinone in cosmetics, and it is not a food additive. The only federal rule touching it covers rubber gloves that contact food.

This is where the US and Europe split sharply. American brands may use Benzisothiazolinone in personal care products, and many household products contain it.

For a stricter reading, Europe applies the precautionary principle. Under that approach a maker must prove a preservative safe before it may be used, rather than waiting for harm to appear.

EU Regulations About Benzisothiazolinone

Europe does not permit Benzisothiazolinone as a cosmetic preservative. The rule works through a positive list. Only preservatives named in Annex V of the Cosmetics Regulation may be used, and Benzisothiazolinone is not named.

The industry asked for permission and was refused. In 2012, the Scientific Committee on Consumer Safety reviewed a dossier requesting 100 parts per million. Its published opinion reached a blunt conclusion. “Until safe levels of exposure have been established,” it wrote, “the use of Benzisothiazolinone in cosmetic products as a preservative or for other functions cannot be considered safe in relation to sensitization.” The committee was unanimous on that point. Its opinion records no minority view.

U.S. And EU Disagreements On Benzisothiazolinone

The two regions reached opposite conclusions on Benzisothiazolinone from the same evidence. Europe treated the allergy risk as disqualifying, while the United States never set a cosmetic limit at all. The gap is procedural as much as scientific. Europe screens preservatives before sale, and the FDA generally acts only after problems surface.

Canadian Regulations About Benzisothiazolinone

Canada permits Benzisothiazolinone in cosmetics. It does not appear on the Health Canada Hotlist, the country’s roster of prohibited and restricted cosmetic ingredients. Canada’s environmental toxic-substances list leaves it out as well. On this ingredient, Canada sits closer to the United States than to Europe.

Can Benzisothiazolinone Cause Skin Allergy And Sensitization?

Yes, Benzisothiazolinone can cause skin allergy and sensitization and this is the main reason for my rating. Benzisothiazolinone is a recognized contact allergen, and Europe classifies it as a skin sensitizer with a legal limit as low as 0.036%.

The potency numbers are specific. Animal testing rates Benzisothiazolinone as moderate sensitizer. Workers wearing vinyl gloves developed allergic contact dermatitis from as little as 20 parts per million. Patch-test clinics now find allergy to it in about 2% of tested patients.

Cases are climbing. The recent papers like Benzisothiazolinone on the Rise and A Case Report of Allergic Contact Dermatitis to Benzisothiazolinone in a laundry detergent show that dermatologists have noticed the issue.

Is Benzisothiazolinone A Hormone (Endocrine) Disruptor?

No study has shown that Benzisothiazolinone disrupts hormones in people. The question, however, is open rather than closed.

European regulators added it to their endocrine-disruptor assessment list in 2025 at Spain’s request, and that review has reached no conclusion. Laboratory work has also reported disrupted thyroid signaling in zebrafish.

Is Benzisothiazolinone Safe To Use While Pregnant?

Benzisothiazolinone raises no specific pregnancy warning. A two-generation feeding study in rats found no reproductive harm, and the amount crossing skin stays low.

Pregnancy is personal, though, and you should consult with your medical provider about products that concern you. My main reason for avoiding the Benzisothiazolinone preservative is allergy, and that reason applies whether or not you are pregnant.

Are There Any Cancer Concerns Linked To Benzisothiazolinone?

No cancer agency has flagged Benzisothiazolinone. It’s absent from the International Agency for Research on Cancer listings, the U.S. National Toxicology Program report, and California’s Proposition 65.

There is an important catch, though. Europe’s safety review records “no data submitted” for Benzisothiazolinone carcinogenicity, meaning the question was never studied. So the clean record reflects missing tests rather than reassuring results.

Genotoxicity was tested, and Benzisothiazolinone came back negative. It does not appear to damage DNA.

Is Benzisothiazolinone Bad For The Environment?

Yes, and its own hazard label says so. Benzisothiazolinone carries the classification for severe, long-lasting harm to fish and other water life. That matters more here than with most cosmetic ingredients. Benzisothiazolinone lives mainly in laundry detergents and cleaners, so it goes straight down the drain by design.

Common Claims About Benzisothiazolinone: What’s True And What’s Not

Claim: Benzisothiazolinone Is Banned In Europe

This is essentially true, though the wording matters. Europe never issued a ban notice; instead, it declined to add Benzisothiazolinone to the list of permitted preservatives.

The practical result is the same. A cosmetic sold in the EU or UK cannot use Benzisothiazolinone as a preservative.

Claim: Benzisothiazolinone Is The Same As Methylisothiazolinone

Benzisothiazolinone and Methylisothiazolinone are relatives, not twins. Both belong to the isothiazolinone family, and both cause allergic contact dermatitis, but they are different molecules with different rules.

Methylisothiazolinone is permitted in EU rinse-off cosmetics up to 15 parts per million and was named Allergen of the Year in 2013. Benzisothiazolinone is not permitted in EU cosmetics at all.

Claim: Benzisothiazolinone Is Natural

No, it is entirely synthetic. Nothing about Benzisothiazolinone occurs in nature, and no natural cosmetic standard accepts it. Neither COSMOS nor NATRUE lists it. A product carrying either certification will not contain this ingredient in its formula.

What I Think About Benzisothiazolinone — And What You Should Do

Benzisothiazolinone is an industrial biocide, and I keep it out of every tier of my recommendations. It belongs in paint cans and cutting fluids rather than on skin.

The reasoning is straightforward. Europe’s own panel declined to clear Benzisothiazolinone. It carries a harmonised sensitizer classification that kicks in at 0.036%, allergy cases are rising, and it’s very toxic to aquatic life.

Here is what I actually do. I check laundry detergents and household cleaners first, since that’s where most exposure to Benzisothiazolinone happens. I also choose brands that publish their full preservative list.

Frequently Asked Questions About Benzisothiazolinone

Is Benzisothiazolinone Banned In Europe?

Effectively yes, Benzisothiazolinone is not permitted in cosmetics in Europe. It’s missing from Annex V, the EU’s list of permitted cosmetic preservatives, so it cannot be used in that role. It remains legal in European cleaning products and paints.

How Toxic Is Benzisothiazolinone?

Benzisothiazolinone systemic toxicity is low, and Europe calculated a wide safety margin on that measure. The hazard lies elsewhere: skin sensitization, severe eye damage, and aquatic toxicity.

Is Benzisothiazolinone Inhalation Safe?

No, Benzisothiazolinone inhalation is not safe. Pure Benzisothiazolinone carries the hazard statement “fatal if inhaled,” which is why I avoid spray cleaners containing it. The diluted amount in a finished product poses far less risk than the raw material.

Is Benzisothiazolinone A Natural Ingredient?

No, Benzisothiazolinone is fully synthetic. It does not occur in nature and holds no COSMOS or NATRUE approval.

Is Benzisothiazolinone Harmful To The Eye?

Yes, in concentrated form Benzisothiazolinone is harmful to the eye. It carries the classification for serious eye damage, and rabbit testing rated it a severe eye irritant.

Is Benzisothiazolinone The Same As Methylisothiazolinone?

No, Benzisothiazolinone and Methylisothiazolinone are not the same, though they are chemical cousins in the same family. Methylisothiazolinone is allowed in EU rinse-off cosmetics at low levels, while Benzisothiazolinone is not allowed in EU cosmetics at all.

Sources

EU SCCS / SCCP Opinions:

SCCS Opinion on Benzisothiazolinone (SCCS/1482/12, adopted 26-27 June 2012) concluded its cosmetic use “cannot be considered safe in relation to sensitisation”; unanimous, with no minority opinion. SCCS/1482/12 (PDF)

Earlier opinion SCCNFP/0811/04 (2004) found the submitted data insufficient and requested a percutaneous absorption study and reproduction toxicity data. SCCS opinions library

Cosmetic Ingredient Review (CIR) Reports:

No CIR safety assessment on Benzisothiazolinone (checked). CIR reports

European Union Regulatory Databases:

EU CosIng entry listed with the function ANTIMICROBIAL only; no Annex entry, so it is not a permitted cosmetic preservative. CosIng record 32133

CLP Annex VI harmonised classification Skin Sens. 1B (H317) with a specific concentration limit of 0.05%, plus Acute Tox. 2 (H330), Eye Dam. 1 (H318), and Aquatic Acute/Chronic 1 (H400/H410), applicable from 01/09/2025.

ECHA substance record REACH registered; endocrine-disruptor assessment ongoing (submitted by Spain, 2025). ECHA activities

Other Regulators:

U.S. FDA: Benzisothiazolinone is not on the prohibited or restricted cosmetic ingredients list, and it is not a food additive.

Health Canada Cosmetic Ingredient Hotlist: not listed (checked).

Environment Canada CEPA Schedule 1 (List of Toxic Substances): not listed (checked).

International Agency for Research on Cancer, U.S. National Toxicology Program, and California Proposition 65: not classified or listed (checked). Note that carcinogenicity was never tested.

PubChem Records (Chemistry, Identifiers, Skin Penetration, Hazard Codes):

The PubChem CID 17520: molecular weight 151.19, LogP, identifiers, and GHS hazard codes. PubChem record

Peer-Reviewed Studies:

Aalto-Korte K, et al. Occupational contact allergy to Benzisothiazolinone, including cases from powder-free PVC gloves (about 20 ppm sufficient to sensitize). PubMed

“Benzisothiazolinone on the Rise” reports increasing sensitization rates. PMID 40443262. PubMed

Lam M, et al. A case report of allergic contact dermatitis to Benzisothiazolinone in a laundry detergent. Contact Dermatitis. 2024. PMID 38925636. PubMed

Natural Cosmetic Standards:

COSMOS-standard approved raw materials: Benzisothiazolinone not listed. COSMOS database

NATRUE certified/approved raw materials: Benzisothiazolinone not listed. NATRUE

Skin Allergy Resource:

American Contact Dermatitis Society (ACDS) Helpful References, including the Core Allergen Series 2020: Benzisothiazolinone is not on the core panel, though its relatives methylisothiazolinone and MCI/MI are. ACDS references

Last verified: 08-02-2026