Methylisothiazolinone allergy

Author: Dr Lynne Gordon, Dermatologist, Adelaide, South Australia. Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, 31 January 2016.

What is methylisothiazolinone?

Methylisothiazolinone (MI) is an preservative. MI was initially used occupationally, in paints, adhesive/glues and cleaners etc, as a mixture with methylchloroisothiazolinone (MCI). Since 2005, it has been widely used in cosmetics and household products, such as moist wipes, shampoos, cleaners and liquid laundry products.

When used in the industrial setting, MI was thought not to be a significant occupational allergen. Subsequently, following extensive domestic use, MI was found to be to be a strong allergen. It is responsible for an “epidemic” of contact allergic dermatitis (2016).

Where is methylisothiazolinone found?

Products commonly containing methylisothiazolinone
CosmeticsPharmaceutical/self-hygiene productsHousehold/industrial products
Foundations/concealers Sunscreens Detergents/cleaners
Bronzers/self-tanners Shampoo/conditioners Fabric softeners/ washing detergents
Eye shadows Bubble baths Polishes
Mascaras Soaps/hand washes/body washes Pesticides
Make-up removers Baby wet wipes Paints
Moisturisers Creams/lotions/gels Adhesives/glues
Wet-wipe make-up remover/moist disposable wipes OTC and prescription medicines
Wet-wipe moist personal hygiene cleaners, sunglass cleaners etc
Latex emulsions
Coolants
Cooling tower water
Pulp and paper industry
  ECG electrode gels Curing agents
    Jet fuels
    Printing inks
    Wet-wipe type cleaning products

How common is allergy to methylisothiazolinone?

Allergy to methylisothiazolinone is extremely common. The European Scientific Committee on Consumer Safety reviewed the literature and in July 2015 banned the use of MI in Europe in all new leave-on products and lowered the concentration for rinse-off products; the concentration is now so low that it no longer functions as a preservative, and probably will not be used. This directive did not include industrial products.

The TGA is currently reviewing use in Australia. In 2015–16 in Australia and New Zealand, patch testing up to 20–25% of all patients tested to MI are positive.

Who is exposed to methylisothiazolinone?

There are two main situations in which people are exposed to MI.

What are the reactions to methylisothiazolinone?

Early on, dermatitis may occur only on part of the exposed skin. Common patterns include:

Later, more extensive and severe whole body contact dermatitis may occur in very sensitive people.

How is allergy to methylisothiazolinone diagnosed?

Methylisothiazolinone allergy is diagnosed from the clinical history and by performing patch tests to MI and MCI/MI mix.

These are both included in the Australasian Standard Series.

Only CMI/MI is available in the True Test Kit and one study in 2015 from Bangkok demonstrated that 27% of those positive to MI would be missed if only MCI/MI mix in aqua was tested.

A positive patch test reaction to methylisothiazolinone may reflect a past exposure and may not be the cause of a current skin problem. However, as MI contact allergy is very common, it is generally relevant.

How can exposure to methylisothiazolinone be avoided?

Once MI or MCI/MI (isothiazolinone mix) sensitivity is confirmed, stop using all cosmetic and work products with this preservative. Tell your family doctor about your allergy.

It can be challenging to avoid MI and other isothiazolinones, as they are in many cosmetic products. Read product labels carefully; they are generally listed towards the end of the ingredient list. Do not use unlabelled products. Brand name or packaging of products can be very similar, however the preservatives may be different. Products within the same brand often contain different preservatives (eg hair shampoos, conditioners, baby wipes, face creams etc). For example:

If unsure, ask your pharmacist or dermatologist for advice or a suitable alternative. Be aware that contact allergy can also occur to other preservatives.

It is also important to avoid exposure to methylisothiazolinone preservative or related preservatives in the workplace.

Highly sensitive people may need to avoid freshly painted rooms for up to 4 weeks.

Cross reactions

All chemicals in the isothiazolinone group may cross react and need to be avoided.

Other preservatives can also cause contact allergy.

Self-testing

Self-testing a product for MI is possible but should be done only after first talking with your dermatologist. An open application test should be done only with products that are designed to stay on the skin such as cosmetics (not including eyeliners or mascaras) and lotions.

Products such as shampoos, soaps and cleansers should not be self-tested, as they contain detergent that may cause irritant contact dermatitis on tender areas of skin in anyone.

Treatment of contact dermatitis due to methylisothiazolinone

People diagnosed with methylisothiazolinone allergy should avoid exposure to all isothiazolinone mix-containing products.

Treatment of contact dermatitis includes:

The labels of treatment creams should also be inspected, to ensure they do not contain isothiazolinone preservatives.

People with severe MI contact dermatitis may require oral corticosteroids.

Alternative names for isothiazolinones

Futher information

CAS number:

Sensitizer:

Patch Test:

Related information

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