When flu season hits, you begin to see hand sanitizer fly off the shelves of stores. People keep the stuff in their car, at their desk, in their purse (if you carry one), and you can also find it in bathrooms, restaurants, and almost every place imaginable. There is always a healthy debate about whether or not antibacterial lotion is truly the best thing to be coating your hands with on a regular basis. However, for those of you who do use antibacterial lotion – be it hourly, after using the restroom, or before eating—I wanted to conduct a small test comparing the different methods of applying antibacterial lotion to determine what is the best mode of application.
As you may have read before, one of the experiments I like to do with kids revolves around microbes that are found on and in people. I give students the opportunity to culture some of the microbes that are present on their body or on things they touch. I use the demonstration as an opportunity to teach children about their own personal microbiome, and how they are really a collection of microbes.
I used this same method to test what bacteria grew on the petri dishes after they were touched by my hands, or after being “sterilized” using antibacterial lotion using different application techniques. Check out the lab report below:
Comparison of Varying Application Methods of Antibacterial Hand Lotion
The objective of this experiment was to learn which method of applying antibacterial lotion to one’s hands kills the most bacteria. Commonly observed methods of applying antibacterial lotion are to 1) rub ones hands together until they are dry or 2) to coat hands, begin to let the antibacterial lotion to evaporate. We also tested for the effect of wiping dry hands on pants or clothing after treatment. We believed that the best method of applying antibacterial lotion is to evenly coat your hands and hold still for 20-30 seconds so that the alcohol is given time to kill any bacteria on the hands.
7 petri dishes coated with standard bacterial growth media (luria broth agar plates)
2 latex gloves (gamma sterilized if possible)
1) Put a latex glove on each hand.
2) Remove the glove from one hand and gently rub the surface of a clean petri dish with finger tips.
3) Apply 1 squirt of alcohol-based lotion to ungloved hand.
4) Using the gloved hand, wipe the ungloved hand to evenly distribute the lotion, continue wiping hands together until lotion has completely evaporated.
5) Gently rub the surface of a clean petri dish with finger tips of ungloved hand.
6) Wipe ungloved hand up and down pant leg 2 times.
7) Gently rub the surface of a clean petri dish with finger tips of ungloved hand.
8) Remove remaining glove and gently rub the surface of a clean petri dish with fingertips of newly ungloved hand.
9) Apply 1 squirt of alcohol-based lotion to newly ungloved hand.
10) Wipe hands together to evenly distribute the lotion, stop wiping once distributed and allow to air dry. Do not blow on or wave hands.
11) Gently rub the surface of a clean petri dish with finger tips of newly ungloved hand.
12) Wipe newly ungloved hand up and down pant leg 2 times.
13) Gently rub the surface of a clean petri dish with finger tips of newly ungloved hand.
14) Incubate petri dishes in 37 degree C incubator. Check periodically for growth.
The following series of photos serves as the data for this experiment. For more photos, visit our Facebook page!
Initial Experiment (click here for more photos):
After 24 hours in incubation (click here for more photos):
After 44 hours incubation (click here for more photos):
We observed the dishes after 24 hours and then after 44 hours. Take a look at the photos and observe the results for yourself. Both the method of applying lotion and rubbing hands until dry and the method of allowing the lotion to fully evaporate level rather similar results. Interestingly, the results clearly show that if you are to touch your jeans after applying the lotion, you have pretty much defeated the purpose of putting on the lotion entirely. Gross!