MI Free February 15, 2026 4 Comments

If you are allergic to isothiazolinones, you’ll almost certainly already be using an appropriate dishwashing liquid or dishwasher tablet. 

However, you don’t always eat at home. Being invited to friends or family for supper, breaking bread with work colleagues in the canteen, or eating with your loved ones at a nice restaurant all mean using crockery and utensils which may have been washed in a detergent preserved with isothiazolinones — quite commonly methylisothiazolinone and benzisothiazolinone.

Is there a risk associated with this? Can traces of washing soap be left behind on rinsed dishes? And are they sufficient to trigger a reaction? 

This is just the kind of work that needs to be done in this field. So I was pleased to come across this Iranian study, just published in Environmental Health and Pollution Research. It set out to begin to answer these questions in relation to methylisothiazolinone, as well as the foaming agent sodium lauryl sulfate (SLS). 

The researchers sampled 100 households and 300 items of tableware — ceramic plates, stainless steel cutlery, and glass tumblers — and used liquid chromatography–mass spectrometry to analyse swabs of their surfaces. 

The results were concerning:

• Traces of both analysed chemicals were detectable.
• Significantly higher quantities of both were found on ceramic plates, and less on steel cutlery and glass tumblers. The researchers suggested that this was due to the rougher nature of plates — and we can speculate that older plates, ‘roughed’ up after years of use, contact with cutlery, and scrubbed down during dishwashing, may be worse than newer ones.
• Shorter rinsing times and greater water hardness increased levels of chemical retention.
• Ingestion exposure was highest with ceramic plates, with 1 in 50 cases “exceeding acceptable daily intake” under worst-case usage scenarios.
• Potential skin exposure risks were negligible.

So, in summary, there’s a risk, with insufficiently rinsed ceramic plates in hard-water areas carrying the greatest.

But it’s also important to bear in mind that the study didn’t specifically consider the allergy perspective, but rather a general human health one. 

People with isothiazolinone allergies are bound to be more vulnerable to the effects than the wider population.

What can you do about the isothiazolinone risk in dishwashing liquid?

Obviously, buy and use only isothiazolinone-free detergents. If you’re looking for some to try, see our listing of Kitchen Products. 

As general advice, try not to overuse your detergents. Wipe particularly dirty plates with kitchen paper to get the worst grease off, so that less detergent is needed when washing.

Perhaps consider investing in an ion-exchange or other water softening system.

Dishwashing soap bars of very simple formulations are worth a try, such as Green Llama’s Solid Coconut Soap Dish Bar (US) or Friendly Soap’s Kitchen Bar (UK).  

Soap bars may require slightly more vigorous rinsing than a liquid, but as the study suggested, it’s a good idea to rinse more thoroughly than you ordinarily might anyway. Warm water may be more effective than cool. If your dishwasher offers extra rinse cycles, use it. 

These methods can reduce your exposure to all ingredients in dish soap which are undesirable. We know that the gut barrier can be impacted by dishwashing preparations. And we know how important that is with respect to allergy. That said, the main risk in this regard appears to be from rinse aids, according to this study in the JACI from 2023, so you may like to avoid using those in your dishwasher.

What about exposure to isothiazolinones when eating out?

This is trickier. You can encourage those close to you, and perhaps even the kitchen staff at your workplace, to use safe detergents, or perhaps even bring your own tableware in these circumstances. But what can you do about exposure at other eateries? 

I have no solutions. You could ask restaurant staff whether plates in alternatives to ceramics are available — such as glass or other ‘smooth’ material — and perhaps order drinks served in their original cans or bottles and drink directly from those, for example. 

I’m sure readers who have been managing this allergy for years have plenty of other suggestions, so please leave a comment if you do.