The science of hand sanitizers
Nirdesh Baral and Sandip Pahari
The recent COVID-19 outbreak has threatened the human existence. With the corona outbreak terms such as “Quarantine”, “Contact Tracing” and “Hand Sanitizers” have also gained popularity among the general public. It is considered as the savior from the COVID-19.
Health sanitizers is a liquid/gel/foam used to disinfect hands instantly. It is considered as convenient method of disinfecting hand where water and soap are not readily available. Hand sanitizer have variety of chemical as their active ingredient but broadly classified as Alcohol based and Non-Alcohol based.
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Direction of use of hand sanitizer includes:
- Apply product to the palm of one hand.
- Rub hands together.
- Rub the product over all surfaces of hands and fingers until hands are dry.
A brisk hand rub with few drops of hand sanitizer can kill highly pathogenic organism making you diseases free. In this Article, we will explore the science behind the sanitizer.
Chemical Composition
Hand Sanitizer were introduced in 1996 in medical settings and was popular since 1990’s due to its convenience. Alcohol based hand sanitizers have variety of ingredients in different composition however hand sanitizer with at least 60% alcohol content is preferred due to its effectiveness. Non-alcohol-based hand sanitizers contains benzalkonium chloride or triclosan as an active ingredient. Department of Drug Administration (DDA) has also released guidelines to standardize quality of hand sanitizer in Nepal.
Raw materials
- Ethyl Alcohol -96% (minimum)
- Isopropyl Alcohol -99.8% (minimum)
- Hydrogen Peroxide – 3%
- Glycerol – 98%
- Sterile/Distilled/Boiled Cold water
DDA recommended standard: Instant Hand Sanitizer (Alcohol Based) Standard 2076
| S.no | Chemicals | Requirement |
| 1 | Ethyl Alcohol or Isopropyl Alcohol Content | 70% to 80% v/v |
| 2 | pH | 6-8 |
| 3 | Microbicidal activity | ≥5 log reduction within 1 min |
| 4 | Hydrogen Peroxide | 0.125% v/v or Chlorhexidine Gluconate content 0.5%v/v may be used. |
DDA recommended standard: Instant Hand Sanitizer (Alcohol Based) Standard 2076
Working Mechanism and effectiveness
The active ingredient of instant hand sanitizers is Ethyl Alcohol. Alcohol gains ability of the microbicidal activity with the concentration of 30% and optimum activity as concentration exceeds 60%. Alcohol kills pathogenic microbes in variety of way such as it disintegrates cell membrane, splitting cell and messing with metabolism of cell. Similarly, non-alcohol-based hand sanitizers with benzalkonium chloride as active ingredient have shown same level of microbicidal activity at just 0.13% concentration but exhibit harmful effects on health.
Handwashing vs Hand Sanitizer: Which is best?
A debatable question obviously arises as both methods are widely used to clean hand. A study has shown that Hand sanitizer is able to disinfect Escherichia coli, Serratia marcescens and Staphylococcus saprophyticus that a regular hand wash could not. However, hand washing has more merits than that of sanitizer.
CDC recommends handwashing than use of hand sanitization as hand sanitizer have various demerits such as;
- Cannot kill wide range of virus including norovirus; Clostridium difficile, which can cause life-threatening diarrhea; or Cryptosporidium, a parasite that causes a diarrheal disease called cryptosporidiosis.
- Is ineffective to work in greasy and dirty hands.
- Fails to remove pesticides and heavy metals residue.
- Health implication such as allergies, dryness of skin and mild irritation etc.
The above points suggest that hand sanitizer must be used as an alternative to hand washing but not as replacement. It is better to hand wash regularly following all six steps. However, best results can be yield if used in combination.
Authors
Nirdesh Baral, 7th Sem BPH Student, School of Health and Allied Sciences, Pokhara University
Email: nirdesh8@gmail.com, Cell No. +977-9816138346Sandip Pahari, Assistant Professor, School of Health and Allied Sciences, Pokhara University
Email: sp.mph15@gmail.com, Cell No. +977-9846261237
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