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Author: Dr Julia Zhu, Dermatology Advanced Registrar Trainee, Greenlane Clinical Centre, New Zealand. Copy edited by Gus Mitchell. January 2022
Benzisothiazolinone (BIT) is an organic compound widely used as an industrial preservative for its antimicrobial properties and has the potential to cause allergic contact dermatitis.
Benzoisothiazolinone, also known as 1,2-Benzisothiazolin-3-one, is an established contact allergen and belongs to a class of molecules called isothiazolinones. Other known sensitisers from this class include methylisothiazolinone (MI) and octylisothiazolinone.
It may be present in:
The US Environmental Protection Agency declared benzisothiazolinone a moderate skin sensitiser. It is banned from use in personal care products in Europe but may still be found in products from other parts of the world.
Benzisothiazolinone can be an important cause of allergic contact dermatitis from paints. Benzisothiazolinone in paints can evaporate continuously at low levels over weeks to months, posing a risk as an airborne allergen to those exposed.
The exact incidence of allergic contact dermatitis due to benzisothiazolinone is not known. However, current literature has not shown benzisothiazolinone to be a common allergen. Benzisothiazolinone allergy is more likely to be due to occupational exposure given the products that it is found in.
Hand contact dermatitis can be a feature of contact allergy to benzisothiazolinone if the individual has direct skin exposure to the allergen after sensitisation. This may appear as a red, itchy, swollen rash that may even be weepy or blistering.
If airborne contact occurs, the affected person may experience dermatitis affecting the face and around the eyes.
Patch testing is the standard diagnostic test with a positive patch test reaction indicating an allergy. As benzisothiazolinone is not a common allergen, it is not included in many of the standard patch test series internationally. It is part of the European comprehensive series and British standard series.
Patch testing details:
For more information on treatment, see allergic contact dermatitis.
It is important to be mindful of products that may contain benzisothiazolinone. When handling paints or cleaning products, it is always useful to wear protective equipment (such as mask and gloves) especially if there is uncertainty around whether a product contains benzisothiazolinone. For personal products, in countries where it is not banned, it is useful to read the manufacturer’s ingredient list to ensure that benzisothiazolinone is not present. This may be found on the manufacturer’s website or by contacting the manufacturer directly.
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