Wednesday, February 8, 2012

Which Kills More Germs: Hand Sanitizer or Soap?

This is the question Grace chose to ask for her science fair.

Yes, those are colored on painted nails. What can I say, I'm raising girls. :)

Since it is so relevant to keeping us healthy, lots of people have been interested in her results so I thought I'd share what our little scientist studied incase you want to replicate it in your own academic setting.

To do the project we ordered petri dishes with pre-poured agar off Amazon. One dish was opened to air for 10 seconds and immediately closed. This was the control. For the second dish, Grace rubbed her hand through her hair for 30 seconds and washed with SoftSoap hand soap for 30 seconds. Then she placed her hands directly onto the agar for 30 seconds. For the third dish she repeated the same process only she washed her hands for 60 seconds. The fourth and fifth dishes repeated the same process with GermX hand sanitizer. And, the final dish was 30 seconds of rubbing her hand throug her hair and no hand washing at all.

She practiced counting and assessing data all at once when she began gathering her results. At 24 hours, 48 hours, and 72 hours she counted the colonies and, obviously, the one with the least germ growth represented the best at killing off germs.

Her results were astounding. Hand sanitizer was FAR MORE effective at every point of data collection. In fact, the 60 second hand sanitizer only had 13 colonies.

This is no soap of any kind (168 colonies).
Wash your hands people!

She was so excited to set up her board (we found the fun foam hands at Hobby Lobby) and explain her results to the many that walked through. In true mother form, I got all teary eyed watching her. I'm going to have to work on that if we are going to do this for years to come. :)

Approximately 1/3 of her student body participated in the science fair, which I thought was an awesome testament to the wonderful teachers and administration that get kids and their parents so fired up about learning that they do optional projects and hang out at school on a Friday night. The kids' creativity was incredible.

As the judges came around, they listened to the children explain their project and gave them a ribbon.

Grace has been carrying it everywhere. She even showed it to her dance teacher yesterday. :)

Overall, this was an easy, interesting science project that I'd highly recommend for science fairs, early elementary ed teachers, or homeschool parents. It really drove home a point that we parents are constantly trying to make. Now Grace wants to wash her hands (because she's seen what is on her hands if she doesn't) and the new challenge is getting her to still use soap. Something about hand sanitizer only after going to the bathroom just seems wrong. So she's doing both. :)

Did your child do a science project? I'd love to hear about it. And, if any involved food/cooking I'd REALLY love to hear about it. That's what she initially hoped to find and we struck out!


  1. What a great project, and congratulations to Grace. Good Job!

  2. we are doing a similar project but with different results... we used a dirty hand in dish 1(just playing outside etc) that same hand rubbed with hand sanitizer in dish 2, another dirty hand in dish 3, that same hand wiped off well with a Lysol antibacterial wipe in dish 4, another dirty hand in dish 5 and the same had washed and scrubbed vigorously with soap and hot water for 30 seconds in dish 6. Incubated at 90 degrees for 24 hours the gel killed almost nothing, the wipe did amazingly well and so did the soap. There was actually some bacteria left on the soap hand, but no fungus, there was a little fungus, but no bacteria on the wipe hand. We did grow a little fungus in our control so we will be repeating the experiment. We are making our own agar.

  3. Great job I'm doing the same project but having difficulty!


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