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 …