Benzisothiazolinone (BIT)

What is BIT and what is it used for?

Benzisothiazolinone is a biocide from the isothiazolinone family. It prevents the growth of bacteria and fungi in water-based products, stopping the detergent from spoiling in the bottle, developing a bad smell or going mouldy.

Although it belongs to the same family as MIT and MCI, its structure is different and it is more stable. This is why it is used on its own or together with MIT, especially in cleaning products, paints and industrial fluids.

Which products contain it?

• Liquid washing-up and laundry detergents
• Fabric softeners and surface cleaners
• Water-based wall paints, adhesives and fillers
• Some industrial cooling and cutting fluids

You should not expect to see it in the ingredient lists of cosmetic products, because it is not among the preservatives permitted under EU and Turkish cosmetics legislation. For cleaning products, ingredient information is usually on the back of the pack or in the ingredient list on the manufacturer's website.

Is it harmful? The scientific assessment

The main health issue with BIT is allergic contact dermatitis. Under EU classification it is a skin sensitiser, and in pure form it can cause serious eye damage. However, it is present in products at very low concentrations.

Current data show that BIT is a weaker sensitiser than MIT and especially MCI. Even so, reactions can occur in people who have already become sensitised to isothiazolinones. In patients who have been patch tested, BIT allergy is generally reported to be linked to paints, adhesives or occupational contact.

Under EU rules, the labels of cleaning products that exceed a certain threshold must carry an allergic reaction warning. BIT is not classified as a carcinogen or an endocrine disruptor.

Who should be careful?

• People with a known isothiazolinone allergy: They are advised to check the labels of detergents, fabric softeners and paints.
• People working in cleaning, painting and construction: Because of prolonged and repeated contact, wearing gloves is important.
• People with hand eczema: Damaged skin is more permeable to allergens; avoiding washing up without gloves helps.

What to do when you see it on a label

Seeing BIT on a detergent label is no cause for concern if you don't have an allergy; wearing gloves and rinsing the product off well greatly reduce contact. If you are worried about residue on your laundry, you can choose an extra rinse programme. When painting, ventilating the room well and not staying in a freshly painted room for long also reduce the likelihood of a reaction in people sensitive to isothiazolinones; some paint manufacturers also offer isothiazolinone-free products for these people. If you have an isothiazolinone allergy, check the ingredient list even on detergents labelled “fragrance-free” or “for sensitive skin”; these phrases do not mean there is no preservative.