RDA's Yeast Experiment Update

RDA's Yeast Experiment Update

Looking for evidence-based recommendations on how to handle your cloth diapers in the presence of a yeast infection? So are we! So the Real Diaper Association launched a series of experiments over the past year and a half to learn more.  The research is ongoing, but here are our findings so far – - and information about how YOU can help as a citizen scientist!

Step One: Getting yeast onto the diapers

Through the generosity of some Candida albicans researchers, we have a supply of yeast that we keep alive on agar plates.  We seed clean cloth diapers with yeast from the plates and let the yeast grow on the diapers (adding apple juice to feed the yeast) for four days before washing (to mimic real life diaper usage).

Step Two: Washing/drying diapers with additives for testing

The goal of the tests is to determine how environmentally-safer alternatives compare to chlorine bleach in ridding the diapers of yeast.  The constant process was the RDA wash routine, http://realdiapers.org/wash, with machine drying (to limit the bacterial contamination of our result interpretation).  Once the diapers were washed and dried, they were swabbed on agar plates.  After 3 days, the plates were read for results.

Using ½ cup chlorine bleach (positive control), no yeast grew on the plates.  Using the RDA wash routine with no detergent (negative control), lots of yeast colonies grew on all fabrics. The additives tested were added to drum after detergent was added at the beginning of the cycle:

  • tea tree oil (brand: Tea Tree Therapy, amount: 1 t*),
  • grapefruit seed extract (brand: Solaray, amount: 1t – 2t*),
  • nonchlorine oxygen bleach (brand: Oxyclean, amount: 5t)

*NOTE: These additive amounts were used in a non-HE toploader, which uses a lot of water (33+ gallons per load). Perhaps using an HE machine with less dilution would allow you to use a smaller amount, because this is a lot (1t ~ 120 drops).

Step Three: Evaluating results

Results by fabric, evaluated 3 days after drying:

Qualifying results

These results are specific to a single machine (brand: Hotpoint, top-loader) in a single location using (hard) well water in southern California. The liquid detergent used was Seventh Generation, and the brands of tested additives are included above.


While we’d love to base recommendations for washing your cloth diapers based on these recommendations, the fact is thatour results are seriously limited.  These tests were designed with the assistance of professional microbiologists and mycologists, who also trained our citizen scientists, but were conducted outside of a laboratory by volunteers.  These results are a great base for further research, but should not be considered conclusive.

Invitation: Have enough extra space to house a card table?  Time and inclination to do some extra loads of laundry and use some fun equipment like agar plates, latex gloves, Bunsen burners, and inoculation loops?  If so, please see below…

Important reminders

When trying to decide how to handle your baby’s rash, first make sure that you’re dealing with yeast by having your pediatrician test for it.  Other culprits like ammonia can often cause a rash but be misdiagnosed as a yeast infection without a positive culture for candida.  Candida albicans doesn’t form spores so if you’re seeing a rash return after bleaching your diapers (and rinsing them well!), you either have a problem other than yeast or you need to address the systemic problem that is leading to recurring yeast overgrowth.  Handling systemic Candida problems should include an evaluation of diet and overall gut health.  Once your child has been diagnosed with a yeast infection, your health professional should give you guidance on how to restore balance to your child’s system.

Our next steps

These are the follow-on tests we’ll be conducting after evaluating our initial results.

  • Try adding tea tree oil to detergent and mixing well before adding to wash to help oil disperse better.
  • Try using less (¼ cup) chlorine bleach.
  • Try using more (¼ cup) Oxyclean.
  • Switch to oxygenated bleach and try that instead of Oxyclean (such as Biokleen).
  • Test boiling diapers at 60C for 2 minutes (which should be 99.9% lethal for Candida albicans).

YOUR next steps? Verifying results…

Since our experiments are so limited, it’s difficult to verify how consistent they’d be under different conditions. These are the tests we’d like to see performed by more volunteers.

  • Retry these tests on other machines, in other locations, using other detergents.
  • Retry these tests with line drying to make certain it remains the same.

To participate as a citizen scientist, please contact us at info@realdiaperassociation.org.  You can also support this work by donating to cover our materials.

Heather McNamara

Executive Director, Real Diaper Association

P.S. Special kudos and thanks go to Liam W., our citizen scientist / intern in Ramona, CA. Liam is a high school student who has learned a LOT about microbiology experiments over the past couple of years and has handled the past year of tests under the guidance of our volunteer experts.

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