Effectiveness of Non-Alcohol Versus Alcohol-Based Hand Sanitizer

PURPOSE

The purpose of this experiment was to compare the effectiveness of alcohol-based and non-alcohol based hand sanitizers in killing bacteria.

I became interested in this idea while walking around the Central Washington State Fair with my mother and saw Germ-X hand sanitizer dispensers outside the animal barns. The dispensers said that Germ-X's formula could kill 99.99% of the germs on your hands. I wondered if their statement was actually true, and if the active ingredient, 62% ethyl alcohol, was the best ingredient to use.

The information gained from this experiment could affect companies that manufacture hand sanitizers. It would also help users of hand sanitizers including: parents, medical workers, food service employees, and those who rent outhouses.

  HYPOTHESIS

My first hypothesis was that the 62% ethyl alcohol based hand sanitizer would be more effective in killing bacteria than the non-alcohol based hand sanitizer. 

My second hypothesis was that the non-alcohol based hand sanitizer would kill more bacteria than water alone.

My third hypothesis was that the 70% isopropyl alcohol would have more effectiveness in killing bacteria than the 62% ethyl alcohol based hand sanitizer.

I based my first hypothesis on Dr. Sally Bloomfield’s statement, "Alcohol-based hand sanitizer provides an effective alternative in situations where soap and water are not available. Based on their safety and lack of antimicrobial resistance, alcohol-based hand sanitizers are appropriate for use in consumer settings."

I based my second hypothesis on the Texas Products Lake Palestine Hand Sanitizer advertisement that stated, “This natural Alcohol Free hand sanitizing gel uses Tea Tree and other essential oils to eliminate germs and bacteria without stripping the skin of essential oils and sebum, which act as natural protective barriers against bacterial infection.”

I based my third hypothesis on the logic that the isopropyl alcohol is 70% alcohol; where as the 62% ethyl alcohol based hand sanitizer has ingredients to soften the effect of dry skin, which I think will also soften the alcohol’s effect on killing bacteria.

Experiment Design

The constants in this study were:

• The purchase date of hand sanitizers and isopropyl alcohol
• The amount of hand sanitizer used
• The amount of time washing the hands
• The motion used to wash the hands
• The water’s temperature
• The time in between washing hands and taking the sample
• The template material
• The type of swab used for sampling bacteria
• The area on hands where sample was taken
• Size of the area where sample was taken
• Method of applying bacteria from swab to blood agar plates
• The type and size of blood agar plate
• The area on the blood agar plate where bacteria was applied
• The time the bacteria grew in the 35ºC incubator
• The method used to measure results

The manipulated variable was the type of cleanser.

The responding variable was the number of colonies visible on blood agar plates after incubation.

To measure the responding variable, I counted the bacterial colonies growing on the blood agar plates, using the naked eye in white light.

 

Materials

Quantity	Item Description
1	Lab Coat
12	Subjects
1	Stop Watch
1	Bottle of Germ-x Hand Sanitizer
1	Bottle of Lake Palestine Hand Sanitizer
1	Bottle of 70% Isopropyl Alcohol
1	Incubator
48	Templates
48	Sterile Swabs
6	Pairs of Gloves
1	Autoclave
48	Swab Containers
1	Black Sharpie
3	Syringes
1	Carrying Case
5	Ziploc Bags
48	Blood Agar Plates

Procedures

I.    Start of the Experiment

a)    Collect the signed permission forms from the volunteers

b)    Obtain materials

c)    Sterilize templates

d)    Gather the subjects

II.    Taking the Unsanitized Sampling

a)    Place the sterile template on the subject’s right hand for the “unsanitized” sample

b)    Swab the subject’s right hand on the palm with the sterile swabs (upward-downward motion, then right to left motion, five times each)

c)    Label one of the containers, using the black pen, with subject’s number (in Roman numerals), which hand it is (R for right, and L for left), and “Un” for unsanitized sample (Example: I, L, Un)

d)    Put the swab into the labeled container 

e)    Throw away template

f)    Place a sterile template on subject’s left hand

g)    Swab the subject’s left hand with sterile swab, using original motion

h)    Put swab in the labeled container

i)    Repeat II a-h for the rest of the subjects’ hands

III.    Lake Palestine Hand Sanitizer Sampling

a)    Teach the motion the subjects use for washing their hands (5 seconds on the top of the hand, 5 seconds on the palm, and 5 seconds in between the fingers, using the tips of the other hand’s fingers)

b)    Have the first three subjects wash their right hands with the Lake Palestine Hand Sanitizer, using the syringe and stopwatch to measure the amount of hand sanitizer and the time spent washing

c)    Place the sterile swabbing template over the palm of the right hand

d)    Take the sample with the sterile swab, using original motion

e)    Throw away template

f)    Repeat step II c-d, except use “LP” instead of “Un” (Example: I, R, LP)

g)    Repeat steps III b-f, but with the left hand

IV.    Germ-X Hand Sanitizer Sampling

a)    Repeat steps III a-g, except use Germ-X hand sanitizer and label containers with “P” instead of “LP’ or “un” (Example: I, R, P)

V.    70% Isopropyl Alcohol Sampling

a)    Repeat steps III a-g, except use 70% isopropyl alcohol and label containers with “IA” (Example: I, R, IA)

VI.    Tap Water Sampling

a)    Repeat steps III a

b)    Have the subjects wash their hands, with the class’ sink for tap water, using the original motions

c)    Repeat III c-g, but use tap water and label containers with “TW” (Example: I, R, TW)

VII.    Incubating the Bacteria Samples

a)    Take the samples to the hospital laboratory

b)    Transfer the bacteria to the blood agar plates by rubbing the swab samples, right to left, 3 times, while rotating the plate 45 degrees, eight times

c)    Label plates with the same label the swab container had, using the black pen

d)    Incubate the sample bacteria for 48 hours at 35°C

e)    Return to the hospital laboratory after 48 hours

          f)    Take the blood agar plates out of the incubator

VIII.    Measuring and Comparing the Results

a)    Count the number of bacterial colonies (with the naked eye under white light) from the right hand subject plates, record results using the labeled initials

b)    Repeat step VIII a, but with the left hand subject plates

c)    Sterilize the blood agar plates and other equipment (using the autoclave)

d)    Compare the results

Results

The original purpose of this experiment was to compare the effectiveness of alcohol-based and non-alcohol based hand sanitizers in killing bacteria.

The results of the experiment were that there was a large difference in the reduction of bacteria for the four cleansers. The 70% isopropyl alcohol had the most reduction, at 88% of the bacterial content killed. The 62% ethyl alcohol had the second most reduction, at 83%. The tap water had the second least reduction, at 27%. The non-alcohol based hand sanitizer had the least reduction, at 15%.

Conclusion

My first original hypothesis was that the 62% ethyl alcohol based hand sanitizer would be more effective in killing bacteria than the non-alcohol based hand sanitizer. 

The results indicate that this hypothesis should be accepted, because the 62% ethyl alcohol based hand sanitizer reduced 83% of the bacterial content on the subjects’ hands, which is more than the 15% the non-alcohol based hand sanitizer did.

My second original hypothesis was that the non-alcohol based hand sanitizer would kill more bacteria than water alone.

The results indicate that this hypothesis should be rejected, because non-alcohol based hand sanitizer only reduced 15% of the colonies on the subjects’ hand, while the tap water reduced 27%.

My third original hypothesis was that the 70% isopropyl alcohol would have more effectiveness in killing bacteria than the 62% ethyl alcohol based hand sanitizer.

The results indicate that this hypothesis should be accepted, because the 70% isopropyl alcohol reduced 88% of the bacteria, and the 62% ethyl alcohol based hand sanitizer reduced 83% of the hand sanitizer. This difference is too close, so more research needs to be done.

After thinking about the results of this experiment, I wonder if there would be any significant difference on the reduction of bacterial content between ethyl and isopropyl alcohol of the same percentage.

If I were to conduct this project again, I would include dry rubbing as one of my control groups. The rubbing of the subjects’ hands could decrease bacterial content. I would also test more subjects to have more trials. Furthermore, I would have compared more cleansers.

Researched by ------ Dalainee V