Why 70 percent Isopropyl alcohol is preferred hand disinfectant not 60 or 80 percent?

While both 70% and 80% isopropyl alcohol are effective hand sanitizers, they have different properties that make them more or less suitable for specific situations. Here's a comparison:

1. Effectiveness:

- Both 70% and 80% isopropyl alcohol are highly effective at killing microorganisms, such as bacteria and viruses, when used correctly. They denature the proteins and dissolve the lipid membranes of these microbes, leading to their destruction.

2. Efficacy Against Different Organisms:

- Studies have demonstrated that 70% isopropyl alcohol exhibits similar or slightly better efficacy against a broad spectrum of microorganisms compared to 80% isopropyl alcohol. This includes bacteria like E. coli, S. aureus, and P. aeruginosa, as well as viruses such as influenza and coronaviruses.

3. Skin Irritation:

- 80% isopropyl alcohol has a higher concentration of alcohol and can be more drying and irritating to the skin compared to 70% isopropyl alcohol. Prolonged or excessive use can lead to skin dryness, cracking, and potential dermatitis.

4. Evaporation Rate:

- 80% isopropyl alcohol evaporates more quickly than 70% isopropyl alcohol. As it evaporates, it cools the skin, which may feel refreshing initially. However, rapid evaporation can also lead to a reduced contact time with the skin, potentially impacting its effectiveness in killing microorganisms.

5. Residual Activity:

- 70% isopropyl alcohol has a slower evaporation rate, allowing it to stay in contact with the skin for a slightly longer duration. This can provide a more prolonged antimicrobial effect, ensuring better sanitization.

6. Formulation and Additives:

- Hand sanitizers often contain additional ingredients like moisturizers and emollients to counteract the drying effects of alcohol. The specific formulation of hand sanitizers can vary based on the desired properties, and higher concentrations of alcohol (like 80%) may require more emollients to balance skin hydration.

7. Guidelines and Regulations:

- Health organizations and regulatory bodies, such as the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), typically recommend 70% isopropyl alcohol as the preferred concentration for hand sanitizers. This recommendation is based on its overall effectiveness, reduced skin irritation, and consistent performance in various settings.

Therefore, while both 70% and 80% isopropyl alcohol are effective as hand sanitizers, most experts recommend 70% isopropyl alcohol due to its combination of efficacy, skin tolerability, and consistent effectiveness against a wide range of microorganisms.