Benzisothiazolinone — Allergy Risk & Safety Profile

Name: Is Benzisothiazolinone Safe? Allergy Risk & Alternatives
Creator: SkinDetekt

INCI: BENZISOTHIAZOLINONE

🔴 High Risk

Key Facts

CAS Number: 2634-33-5
Category: preservative
Risk Level: high
Common Allergen: Yes
Found In: shampoo, cleaning products

Is Benzisothiazolinone safe in cosmetics?

Benzisothiazolinone is rated high risk in cosmetic products. It is a known allergen that can cause contact dermatitis in sensitized individuals. Safer alternatives include Phenoxyethanol, Sodium Benzoate, Potassium Sorbate. Commonly found in shampoo, cleaning products.

What is Benzisothiazolinone?

Isothiazolinone preservative similar to MI. Increasing sensitization rates.

Allergy & Safety Information

Benzisothiazolinone is classified as a high-risk ingredient. It is a known cause of allergic contact dermatitis. Individuals with sensitive skin or a history of contact allergies should avoid products containing this ingredient. A patch test is recommended before first use of any product containing Benzisothiazolinone.

This ingredient is classified as high risk from an allergenicity perspective. It is a recognised cause of allergic contact dermatitis with a relatively high sensitisation rate in patch-tested populations. People with a history of skin reactions to cosmetics, or with conditions such as eczema or sensitive skin, should exercise particular caution.

About Preservative Ingredients

Preservatives prevent microbial growth in water-containing cosmetic formulas. Without them, products would spoil within days. However, preservatives are among the most common causes of allergic contact dermatitis — they must be present in high enough concentrations to be effective, yet that same efficacy can irritate sensitised skin.

Relevance for Benzisothiazolinone: If you react to one preservative, you may be cross-reactive to others in the same chemical family (e.g., isothiazolinones, formaldehyde releasers, or parabens). Checking the full preservative profile of every product you use is the most reliable way to identify your personal trigger.

How to Identify Benzisothiazolinone in Products

Cosmetic ingredients are listed by their INCI (International Nomenclature of Cosmetic Ingredients) name in descending order of concentration. To check whether a product contains Benzisothiazolinone, scan the ingredient list for its INCI name exactly as it appears above. Ingredients present at 1% or less may appear in any order after the 1% threshold.

Product types to prioritise checking: Shampoo, Cleaning products. These product categories are the most common sources of Benzisothiazolinone exposure based on formulation data.

Not sure if your products contain Benzisothiazolinone? Paste the ingredient list into the free ingredient checker to scan for Benzisothiazolinone and other allergens automatically.