MI in laundry detergent – can it really be safe?

In January 2018, a fascinating study was published in the journal Clinical and Translational Allergy, which shook the isothiazolinone-allergy community. The open-access paper can be read here.

This was the key conclusion:

The use of MI in laundry detergents is safe for the consumer if these products are used according to the instructions in the normal household setting machine wash.

In other words: MI in laundry detergent is rinsed out of a wash cycle, and therefore any clothing and bedding should pose no risk for allergic consumers.

This certainly challenged the experiences of many — who’ve had symptoms after overnight stays at hotels, for example.  

I posted the research on Facebook, and it drew a lot of questioning comments from MI-allergy folk, which you can read here.


How was the study conducted?
It’s fair to say the researchers did a lot of laundry …

For each cycle, they used an ordinary load of mixed dirty clothes and (MI Free) laundry detergent. Samples of three pieces of test fabric were added to the washes — one cotton, one polyester / cotton blend, one just polyester fibre — and MI was added in three concentrations in separate washes — 1,000ppm (parts per million, i.e. 0.1% — far higher than ordinarily found in laundry liquids), 100ppm (0.01%), and zero.

The textile samples were dried, and washed either once, or 10 times. 

The level of MI was measured by HPLC [High Performance Liquid Chromatography]. 

While MI was detected in items drenched with washing powder but not washed afterwards (no surprise there …), MI could not be detected in any laundered specimen. The detection limit was 0.5 ppm.

For a visual representation, I’ll reproduce the table from the paper here …


Contact with research team
In the intervening weeks, I’ve been in touch via email with the research team. I put a few questions to them, which one of the team’s members, Professor Torsten Zuberbier, of the Department of Dermatology and Allergy at The Charité, Universitätsmedizin Berlin in Germany, has kindly answered …

1.     Your study did not take into account handling of MI-containing detergent. Drops splash. Liquids get spilt. There is aerolised exposure when a machine is active with detergent inside. Those with MI allergy would not risk this exposure.

TZ: I agree and for MI allergy patients, I would not suggest using an MI containing washing powder. Luckily, there are washing powders/detergents available which are packed in single dosage plastic bags (e.g. Persil Caps) which are manufactured without preservatives. The only reason, why a preservative is contained in washing powder or in fluid washing solutions is, that the consumers want to keep them for a long time in a moist environment and that germs and fungi get into the washing powder, which can be a serious health hazard. Thus, the findings are still important for MI allergy sufferers, because they know that if they use washed clothes, e.g. in a hotel like towels or bed linen, there is no risk for them.

2.     Powder was used in your research, but powder is rarely preserved with isothiazolinones. Where reactions have been reported, it has been due to isothiazolinones in liquid detergents. Might the results have been different had these been used? 

TZ: No, absolutely not. We have checked both (data unpublished).  

3.     It’s not only MI — but BIT is also used, and others such as MCI and OIT. Could these combinations have a different impact? Could other ingredients — such as fragrance compounds, which remain in fabric — affect the behaviour of isothiazolinone molecules, making them likely to be left behind too? Were fragrance free detergents used?

TZ: You are right. Of course, many ingredients in washing powder, but also in all other products of daily life, can cause allergies, and therefore, with the foundation work we’re doing, we closely do a risk assessment and suggest to use fragrances only below a threshold which can be sensitizing. Luckily, for many chemicals, this threshold is known. However, much more needs to be done to ask the industry to adhere to these levels.

4.     Could other variables — tumble-drying versus line-drying, heavier washing loads, different waters (hard / soft) — affect outcomes?

TZ: We also looked at the wet cloth directly out of the machine. Therefore, drying has no effect. Heavier washing loads is not using the washing powder according to the recommendations and, of course, if you press clothes into a washing machine, the water rinsing these clothes will not be sufficient. But this is something which everybody should be aware of, that it is certainly not good to overload a machine. 

It’s clear from correspondence that the team is highly confident in the accuracy and importance of the results. In a subsequent email, Professor Zuberbier added:

My opinion in MI allergy is that currently the biggest problem remaining is wall paints. Especially, as unlike in cosmetics, people cannot escape unwanted exposure if paints are used e.g. in an office by the employer. Here I would certainly support a directive demanding allergy friendly paints and also glues for carpets etc. in public places.


Outstanding issues, and questions

Professor Zuberbier has told me he is keen to read the views of those with MI allergy in response to the research, and will try to answer additional questions if you leave them in comments below.

I have outstanding concerns, including on the use of MI-containing fabric softeners in addition to laundry detergents, and the use of other isothiazolinones, including with fragrances, but I’ll hand over questions and comments to you — the consumer with isothiazolinone allergy. I look forward to hearing them, and your experiences … 


  1. Nancy Po

    I am in the UK and my washing machine (a Hotpoint) does not seem to use much water for rinsing or even washing. could this be part of the problem and could hotels (where I have reacted) be using too much detergent and putting too much washing loads into their machines. It’s all very well saying hotels etc are safe but if we do not’ know how they are doing their washing then we cannot be assured of not reacting.

    1. Louise

      Hotel laundry will typically be done much faster than domestic loads (usually outsourced to a laundry) and yes you will have no idea what fabric softener they are using. As Mi is commonly found in fabric softeners this is likely to be the culprit for anyones reaction to hotel bedding.

  2. Paul

    I applaud the effort to generate real data. I haven’t been able to read the full paper with the methods, as far as I see the research really only shows that the MI was diluted by washing. That’s unsurprising, and doesn’t really answer many questions.

    As the residual concentration was below limit of detection (0.5ppm) it doesn’t tell us how much MI remained in the fabrics after washing, only that it’s less than 0.5ppm.
    I don’t think we know how much MI residue would be immunogenic to a sensitized individual? We also don’t know if a real world washing machine clogged up with dirt and limescale rinses as well as the test model.
    Would be quite wrong then to conclude that MI in washing liquid is safe for a sensitized individual in this case. We simply cannot conclude that from this data but I’m not sure that is what the researchers were concluding? I think their conclusion was on the general safety for all consumers. You might conclude peanuts are safe in supermarkets, doesn’t mean people with peanut allergy should buy them.

    HPLC is not especially sensitive. Maybe MS, or an antibody based technique such as ELISA would be more sensitive and more informative as to residual / retained MI.
    You might quantitate the MI concentration in the final rinse water, then measure the retained liquid in the fabric (by weight) and hence deduce residual MI.

    So many questions remain to be answered:
    What is an immunogenic concentration of Isothiazolnine.
    Do Isothiazolinones bind to fabrics in any way.
    How is isothiazolinone released from fabric in skin contact.

    1. Rebekah

      To add to the above comment’s excellent points; I question whether the study successfully accounted for thise with existing isothiazolinine allergy. There is interesting UK based Research evidence that photoaggravatied (Sunlight) MI reactions occur. Is it possible that sunlight exposure on textiles previously washed in MI/ CMIT/BIT might in some way reactivate the fabric /textiles and cause photoaggravated isothiazolinone allergy skin rash responses? (I have experienced this and we did then conduct a skin patch test (SPT) with a section sample of the very same fabric (a rayon /nylon blend shirt) without positive result. (no reaction was observed from the same fabric sample during SPT). Does the textile composition effect the Isothiazolinone (as well as orher allergens such as fragrance ) interactions or change results of textile washibg tests?

  3. Peggy

    Then please explain to me what causes me to have blisters, swelling and itching after using liquid detergents with MI? I was patch tested and my only reactions were to MI (severe and within and hour – couldn’t wear that patch for the 3 days) and gold. Am I to think that maybe there is gold in laundry detergent? There is something flawed in this test.

    1. Paul

      The conclusion in the paper is I think at best badly worded, else it’s just plain wrong.
      It says “…safe for the consumer”.
      I think that sentence is incomplete to the point of being misleading.
      It should have had a qualifier something like “safe for consumers who are not already allergic to Isothiazolinones”.

      1. Rebekah

        Agree. The wording is misleading and only appears to offer protective benefits for the manufacturer not the consumer.
        What is causing these severe laundry lroduct reactions ? I see rashes reported all over re web: Amazon produxt reviews alone ahow that we have a problem with what is in these laundry “care” products and studies should continue to test all substances commonly used in laundry products in order to identify the specific substances of concern.

  4. Dana Todd

    I have some feedback and questions. I’m definitely NOT a scientist, just an MI sufferer. I run the big Allergy to MI page on Facebook, and posted there as well:

    1. This study only relied on instrumentation, not human assessment. Those of us sensitized can react to as little as 3 ppm. Maybe we’re detecting something the machines aren’t?
    2. We can’t all be crazy here; thousands of us report reacting to clothing and sheets that have been washed with MI or BIT-ingredient laundry detergent. It happens even without us knowing the stuff was contaminated, so it can’t be all in our heads. I wonder why the researchers aren’t asking this same question: WHY??
    3. I’d like to see the data for the liquid detergents; we don’t really know what level is being included in those formulas since it’s not disclosed.
    4. I’d like to see them include BIT, which is potentially more reactive to us and has a higher allowable amount in formulas. It’s also quite common in US detergents such as Tide and All. BIT is documented as a known sensitizer, and thus may be more potent than MI. Throw in OIT for bonus points, since it’s now sneaking into products as well.
    5. I’m very glad to see that the research team is concerned about paints and glues/carpet adhesive, which I think is the next biggest area of concern for us. It’s become nearly impossible to find commercial paint products without MI or BIT, and the selection is limited in color/style. I’d also like them to look at air conditioning as well, which seems to be reported frequently. And also, fabric treatments (furniture, leather, new clothing).

    Overall, glad the scientific community is still looking at isothiazolinones, and hoping that they will continue to explore the safety and allergy risks.

    1. Prof. Torsten Zuberbier

      Dear Ms Todd,

      Thank you for your feedback. I’m happy to reply to the points you raised.

      Concerning the points 1 and 2 raised it can be stated, that the detection limit is far below the 3 ppm some very sensitized persons react to. However, other factors may lead to eczema caused by clothes. I’ve investigated this area in the past extensively as many employees of hospitals had problems with hospital uniforms when the supplier had changed. In the end, the reason for the examiners reaction was not the washing procedure but the nature of the fabrics itself which became extremely rough depending on the washing and ironing procedures. This is called irritant contact eczema and of course for those suffering from it is as bad as allergic. Very frequently irritant contact eczema occurs in areas where previously allergic contact eczema has occurred due to the fact that in these areas homing receptors for t-lymphocytes are more actively expressed.

      Regarding point 3: Liquid detergents were used in the study and in Europe at least the whole ingredients need to be declared on the packaging. The manufacturers also have to insure that no relevant amounts of any contaminants are in the product.

      Regarding point 4: BIT has also been investigated, the results were the same but this has not been published as we wanted to concentrate on the major issue MI.

      Regarding point 5: I could not agree more, we need more research funding to investigate all areas of life in regard to human safety. In Europe the REACH program has helped a bit but more needs to be done.

      However, I also want to give a warning: If MI is completely banned, most likely more dangerous preservatives will be used in the future. This has already happened due to the public concern of parabens which now have turned out to be less problematic than MI regarding contact allergies.

      It needs to be known that only 50 preservatives are allowed in the European Union and not all can be used in all products due to the chemical properties. Furthermore, many of them are also problematic due to contact allergic reactions. In addition, environmental properties need to be considered as well.

      In general it also needs to be stated that a lot can be done if consumer behavior changes. Nobody needs a liquid washing detergent as in powders preservatives are not needed. The same holds true for wall paints, in that case consumers can of course accept a limited range of colors and other changes in the properties like not being able to keep rests of the paint for a year or two. Also in the area of air condition, it clearly needs to be said that air conditioning is not good in general for your health and the environment. Still many consumers want air conditioned homes.

      So the summary of my statement is: We should be careful, we should be trying to find good alternatives, but it’s not always the best alternative to be radical and ban products but rather to consider where and how it is appropriate to use them.

      Best regards
      Prof. Torsten Zuberbier

  5. Mike charnecki

    Me too, once we started using MI free laundry detergent it was a night and day difference! Once our daughter came over and used our washer and she used an MI detergent in our machine I reacted to it pretty bad when my wife did my under garments in the next load. It is terrible to have this problem in the private areas!!! We need MI out of everything!!!!

  6. Melissa

    How are the researchers funded? Why were only half of the conclusions published? Why was 0.5 ppm chosen as the threshold and what allowance was made for reactions occurring below that limit, which is anecdotally the case?

  7. June

    Why can’t MI just be removed . We were getting along fine without it . It’s in almost everything we buy now .Few that haven’t added it. Alot of people have problems with MI and don’t know it’s causing a problem and just keep moving from one product to another trying to Find something that doesn’t cause skin rashes. Some companies don’t list all ingredients and you have call them to find out what their products contain . Couldn’t they just list in capital letters “Contains “ No MI “
    Eventually we lived better or just as good lives without MI . Of people making big money on it wouldn’t agree .

    1. MI Free (Post author)

      I know it’s tough, June. I’ll try to explain. MI is a preservative, and a very good one. We weren’t getting along fine without preservatives before, I’m afraid – without preservatives, products would go to waste, have a short shelf-life, be more expensive, be a health risk. We have other preservatives, but we need a variety of preservatives because if we used the same ones over and over, those people allergic to them would have no options. I’m more with you on labelling. Cosmetics company must declare ingredients, and while declaring ‘no mi’ or ‘mi free’ would be a help, there is a bit of a crackdown in Europe on this ‘free from’ labelling because some cosmetic scientists (wrongly in my view) and cosmetic companies see it as alarmist. Some still do. I don’t know which country you’re in, but detergents must declare their preservation in the EU, and I think almost all do in North America. There are safe lists on this site for you to explore, but if you’re struggling to find a particular product, ask and I’ll see if I can help. Best wishes, Alex

      1. Benita Little

        I spent 3 1/2 years itching in my private areas which eventually went to my hands and scalp. You could see nothing on me. It was so bad in my private areas that I didn’t know if I wanted to go on living. Then it started to show redess on me. Patch test positive for MI and I got rid of MI laundry detergents and other products. Gone almost over night. They are wrong about the laundry detergents. Period!THEY ARE WRONG.

  8. Claire Bennett

    I have just discovered I’m a MI sufferer (blisters, itchy arms neck etc lasting for 6 days) after using Aussie Shine Miracle Conditioner which of course contains both Methylchloroisothiazolinone AND Methylisothiazolinone. This is a leave-in product which I thought the EU had banned. Why are they still allowed to sell this toxic mix?

    1. MI Free (Post author)

      Sorry to hear this, Claire. Are you sure the conditioner isn’t to be washed / rinsed out? I think it’s classed as a rinse-off product if so. If you choose Hair Care above under cosmetics, you’ll find lots of articles with safe options for specific hair needs. Best wishes, Alex.


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