If you're dealing with water damage building interiors, or just wondering what is the best way to clean textiles and clothing that might have become mould contaminated - you might be thinking, why can't I just put them all into the washing machine? Your next question might be: is there something I can do to the washing cycle that will help reduce the population of any germs that might be on those textiles? The answer is yes, there is an optimal way of washing your clothing to remove specific germs like classes of fungi that cause skin and nail infections. These fungi are termed dermatophytes and are superficial fungal infections that colonize the skin, hair, or nails.
This group of fungi thrive in moist areas of the skin and are easily transferred to clothing and towels and they are also found in soil. The statistics around dermatophytes report that 20 to 25% of the world's population is currently infected with a dermatophyte fungus.
A paper that was published in late May 2022, looked at whether you could freeze material contaminated with dermatophyte fungi, or heat them up in a laundromat or domestic dryer, or whether it was best to wash them – and if so, what’s the best way to reduce the viability of these dermatophytes?
This is an interesting question because although dermatophyte fungi are specific causative agents of skin, hair, and nail infections they nevertheless represent a class of fungi that if we understand how they respond to the washing cycle - then this could extend to other types of fungi found in the home, on the floor, or on porous personal items of personal property that might benefit from being washed.
So the central question of this live stream is: hot cycle versus cold cycle versus heat drying versus freezing - which is better?
To answer this question, I'm going to summarize the key findings of a paper that came out in the Journal of Fungi which looked at how to test between these different treatments.
What the scientists did was deliberately contaminate gauze pads with three of the most common fungi that affect humans (Trichophyton tonsurans, Trichophyton rubrum and Trichophyton interdigitale). We know the effects of these fungi when they attack feet and other moist skin areas and cause, for example, Athlete's Foot. We should also respect the fact that these fungi are easily transmitted. Think – of contact with infected individuals or even skin contact with inanimate objects like flooring.
And so what the scientists did was they deliberately infected small gauze pads and then cleaned them in different ways. They looked at the recovery rate for the dermatophyte fungi. Successful cleaning meant there were no fungi recovered.
The first treatment looked at how temperature and cleaning time impacted on fungal recovery. The next question for the washing machine method was whether adding detergent helps? Another cleaning method looked at whether freezing the textile gauze pad could kill the fungi?
The results are compelling:
• Low temperature washing for example, at 40 degrees Celsius for 100 minutes with or without detergent did not reduce the viability of Trichophyton fungi.
• Increasing the temperature to either 60 degrees Celsius or 90 degrees Celsius for either 100 minutes or 150 minutes resulted in the loss of viability for Trichophyton fungi.
• The higher temperature was effective with or without detergent.
• Unfortunately, heat drying the contaminated material in either a domestic machine or a laundromat machine for anywhere from 10 minutes to 150 minutes, did not reduce the population viability of Trichophyton fungi.
• And somewhat counter-intuitively, it was not possible to freeze the fungus and cause it to stop growing even if freezing was carried out for one day, two days, or even seven days – the persistent viability of the Trichophyton fungi was preserved.
The take-home message, therefore, was that domestic washing machines with or without detergent are highly effective at removing dermatophyte fungi like Trichophyton.
Furthermore, despite the purported case for the energy-saving and environmental protection benefits of cold water washing, the science says that cold water is not effective at eradicating dermatophytes and may increase the risk of cross-contamination.
Overall, the most up-to-date research suggests there are no differences between laundering with or without detergent but you need to use the hot cycle set to at least 60 degrees Celsius to eliminate dermatophyte fungi like Trichophyton.
Akhoundi M, Nasrallah J, Marteau A, Chebbah D, Izri A, Brun S. Effect of Household Laundering, Heat Drying, and Freezing on the Survival of Dermatophyte Conidia. J Fungi (Basel). 2022 May 23;8(5):546. doi: 10.3390/jof8050546. PMID: 35628801; PMCID: PMC9143173.