How Clean Are Your Dishes?


Recently a group of European scientist found that our dishwashers may be hosting a once rare organism, the Black Yeast Fungus, (Exophiala dermatitidis or E. phaeomuriformis).  These organisms were once rare in nature, but have apparently taken a liking to the harsh, hot, moist, area around the seals of our dishwashers.  Upon reading about this, I immediately inspected our dishwasher.  I had to look closely as we try to keep the dishwasher clean but guess what I found at the inside bottom of the door seal?  Yes indeed, in a spot that was not readily visible unless you took out the bottom tray and stuck you head inside, a build up of a black coating.  Of course I don’t know if it is the specific organism referred to in all the recent publicity, but its looks sure fit the part.

These fungi are very tolerant to extremes of temperature, salt, acidity, alkalinity; and don’t mind the dishwasher detergent at all. I found a quote from one of the microbiologist researchers, Nina Gunde-Cimerman, that seemed to be quite alarming.

“We tested the dishes after they had been cleaned in these dishwashers and they were full of this black yeast, so too the cutlery that you put in your mouth. We just don’t know how serious this could be.”

These statement were also attributed to the researchers:

“The invasion of black yeasts into our homes represents a potential health risk”

“The discovery of this widespread presence of extremophilic fungi in some of our common household appliances suggests that these organisms have embarked on an extraordinary evolutionary process that could pose a significant risk to human health in the future.”

The first thing that I wonder is how dangerous these fungi really are to normally healthy people. I am reminded of the sometime hysterical press in recent years that could make you think all of our homes are unfit for habitation because of mold spores.   Yes some homes are really infested, but the levels in the vast majority of houses seem to pose no threat to otherwise healthy occupants.  Maybe that is the case here also?  Specifically it is stated that these fungi are a real danger to Cystic Fibrosis patients.  That is surely an important bit of information for these people, their families, and their doctors.  But it really says nothing about the risk to the rest of us.

I found that Frank Odds, a Professor of Medical Mycology at The University of Aberdeen has some thoughts on the risks:

“There’s absolutely no reason why anyone should be upset by finding any kind of fungus around their house. Yes, they cause infections, but luckily for us they’re very rare, We breathe millions of mold and spores and yeast particles every minute of the day and we seem to be well adapted to not being affected by them…  The exception is for people who are very ill, are immunosuppressed, or have had transplantation surgery”

I found several articles that state these fungi are common on shower curtains and along the edges of bath tubs and sinks.  That seems questionable to me as I always thought that stuff was mold, not fungus.  That would also go against the statement by the researchers that these fungi where, until recently, rare.  At least in many of the showers and baths I have frequented over the years, that black stuff was anything but rare.  I have always had to keep is at bay with periodic cleanings with bleach.

For now I will just clean off the inside of our dishwasher more frequently and keep an ear open for further news about any real risk.  With five people at home this summer, I don’t think we are going to retire the dishwasher anytime soon!

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Will Sig
1 Steve

Thanks for taking the time to write posts like this. This issue is very interesting, and I will file it away in my head. We have a shower that is similar to the one you describe, and I have to take bleach to the shower and ceiling on a regular basis. I think living in a humid coastal environment makes it worse.
On that note, we’ve had a pretty good year for tomato growth so far, and are just starting to get the little yellow cherries (orange sungold… aka tomato ambrosia!)… but now the fog seems to be rolling in each day. 🙁 We’ll see how the plants do.
Anyway, just wanted to say GREAT POST, and please keep writing them.
PS. Hope your tooth is doing better.
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2 Will

Thanks Steve! I planted the yellow cherry tomatoes too this year and they are starting to come on strong. I have had several Romas also and a few of the early varieties. Overall it has been a cooler and wetter than normal spring and summer so all the vegies are a bit late. Just picked the first zucchini, yellow squash has been producing for only about a week, today got the first cuke. All my peppers are just barely blooming now, so it will be a while on those.


3 Tony McGurk

I am sitting here looking at my coffee cup & toast plate now thinking Yucko!!!


4 Will

Confused by coffee too are you. I am heading over to read about that as I have the same problem. It may be because I only drink coffee a few times per month and then decaf at that.

I really like your new avatar!


5 Jan

Will, newsflash, decaf is not coffee!! On a more serious note, the process that coffee goes through to decaffeinate it is seriously bad using extremely high heats and chemicals – same for instant coffee – it doesn’t stop me drinking it occasionally but I tend to go more for brewed coffee now with freshly ground beans.
Tony’s cartoon reminds me of a great advert in Brisbane which is a man going into a shop to buy a bottle of milk and the lady asks him what type – skim, low fat, full fat, lactose free etc etc, whoever would have thought there would be so many choices for this basic product? The bloke looks totally mind boggled and says, I just wanted a bottle of milk!!


6 Jan

I am sending this link to the people I know who have dish washers – obviously I don’t! But this is quite scary none the less.


7 Will

I wonder what percentage of people do not have dishwashers? When I was young and single it seemed unnecessary. But once I had a house full of kids, it seemed like something that could not be lived without.


8 Binky

Another case where you really don’t know what to make of the report. As you ask, is it dangerous or not? At what levels? And to whom? I guess I won’t worry too much about it, but it isn’t exactly an appetizing thought.
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9 Will

I’m not too worried either. I did give the inside a good cleaning though!


10 Lynda Lehmann

It’s a little scary, Will, because we don’t know how much these microorganisms will proliferate or ultimately effect our health. But as you pointed out, we have been living with these forms of life for millennia and rarely do they cause harm.

Indigenous peoples all over the world have lived in much closer contact with molds and fungi than we do in the “modern” world. And I don’t remember ever hearing of plagues or mass extinctions caused by mold. Now if you want to talk about the fungus in bat-dung, that may be a different story!


11 Ann

Mold can lurk in the least suspicious places, like in the refrigerator door seal, on damp unwashed clothing and even on clean clothing left in the washer tub for more than a few hours. I have never been fond of dishwashers, I find it more effective to do the dishes by hand, but we are a family of three.

Mold can cause allergies in sensitive people.
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