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Clove oil and mould

April 12, 2012
Let’s check the science: Is clove oil the panacea for cleaning up household mould?

Summer’s over, and in my part of the world it’s time to clean the mould from the doors after the heat and humidity of the wet season. It seems to grow only on the doors and other panels that painted with high-gloss paint.

I’m told I should use clove oil in water to kill the mould. After the Brisbane floods last year, it was all the rage for cleaning up waterlogged houses. Apparently suppliers could not keep up with the demand, and the price went through the roof.  Clove oil is now regarded as the magic solution for cleaning up mould. Is this justified?


This article assumes you are happy to accept science as the best way of discovering the truth about the natural world. If that’s not the case for you, why not have a look at Trusting the science first?

The promoters’ arguments – science or red flags?

There are no really extravagant claims made for clove oil. Generally, the promoters  say that there is a history of using clove oil for cleaning mould, and that it inhibits or kills the mould. For example, see here. The main red flag is that there is seldom any evidence presented.

Being skeptical

I’m prepared to accept that clove oil can kill fungal spores (although I’ll check on that). But I’m not sure that this is of any use to me. Now that summer is over, the warm humid conditions that I know are required for mould growth have gone. Even if I use plain water, which will remove all visible mould but not kill it, it won’t regrow until next summer. And I know that mould is everywhere in the environment and that the spores spread profusely in the air. So even if I kill every fungal cell on each panel, they will be easily contaminated again. What would really impress me would be the ability of the clove oil to remain as a coating on the panels, so that it prevented the mould from growing the next time the appropriate conditions arrived. Somehow, I doubt it can do this, because the oil seems very volatile (witness the odour) and I reckon it will all evaporate well before next summer.

The scientific evidence

A quick web search reveals there’s quite good evidence that clove oil inhibits and kills fungi in vitro, probably due to the main component, eugenol. See here, here, here, here, here. Unfortunately, I couldn’t find reports of any trials that tested the effect of clove oil (or other oils) in real-life, controlled situations. Some websites tended to recommend chlorine bleach for treating mould infestations; others were adamant that it should not be used.

There’s a good overview of clove oil here. It explains that “eugenol is anticipated to be short-lived in the environment, and is rapidly dissipated and degraded via volatilization and atmospheric decomposition”. Just as I thought!

I did find out why mould prefers the surfaces painted with high gloss paints – apparently they are based on natural linseed oil, which the fungus can use as a nutrient, whereas most other paints are based on synthetics.

DIY evidence

I could carry out a preliminary trial myself. I’d need to find a number of panels in my house that are exposed to fairly similar conditions, clean each one with different substances (say clove oil, water, bleach, sugar soap and tea-tree oil), then wait and see what happens next summer.

Conclusion

From what I’ve been able to discover, clove oil is not for me. It may be good where mould has contaminated enclosed places, and the conditions favouring mould growth remain active, such as flooded buildings or air-conditioning vents. But it’s not magic, and in my case, I don’t see any evidence that it will make any difference. Basically, the only way to eliminate mould growth is to remove the source of moisture, and the change in the weather will do that nicely for me. It’s just a matter or removing the nasty black coating at the end of each summer.

This is one of ScienceOrNot’s Let’s check the science series.

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2 Comments
  1. Karyn Amoore permalink

    I am unsure why in this study you did not mention vinegar (white) solution 10% in water for killing mould. This is a well known treatment to kill AND inhibit mould, but you would probably need to test it in cultures or in your environment at the START of summer when you claim the mould grows best… I see you use research as your method, but try vinegar in situ to experiment/investigate. Try at the beginning of the mould growth period (summer), not just one lazy application per year expecting a miracle cure for every mould spore in future…!!? ;)

    • Karyn, I didn’t mention vinegar because this article was specifically intended to investigate the effectiveness of clove oil in combatting mould. I’m sure there are many substances that are effective for that purpose, but clove oil is not very good for most situations.
      I haven’t been into it in great detail, but I suspect vinegar is likewise not very effective for my situation. Yes, acetic acid (the active component of vinegar) is a mould inhibitor. That’s why it’s used in pickling. But like clove oil, it will soon evaporate from the surfaces that have been treated. So while it may kill or slow down the mould on application, it won’t be too long before the surface becomes colonized by more spores.
      I appreciate that vinegar is a useful substance, but for my money, in some circles it’s regarded as a panacea for all sorts of things and that reputation is not deserved. It’s a weak acid. Acidic environments don’t suit some pathogens, but it doesn’t go much further than that. If you need an effective fungicide, there are more efficient options.

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