Blog,  Fun Facts Friday (Science Edition)

Alcohol vs Bacteria

I was at a gathering and someone suggested that a lady could rinse a cup with some alcohol because it can “kill germs” and somehow, I became annoyed. So I used that opportunity to school him a little on microorganisms 😉.

I’m here to teach you too 😅

I remember when I learnt that 100% alcohol cannot kill microorganisms, but 70% can. This didn’t make sense to me. I’m like, how is that possible? 😅

In the laboratory, we use 70% alcohol (especially ethanol) to sterilize work benches, our hands, laboratory bottles, and some equipments.

A lot of hand sanitizers also contain some alcohol.

Scientists have established that 50-80% alcohol is optimal for killing microorganisms.


  • 100% alcohol evaporateS fast, and may not have time to penetrate the cell wall of bacteria 🦠
  • 100% alcohol, can inactivate bacteria, but not kill it. So, the organism may continue to function under favorable conditions.

This might give you an idea as to why 50-80% can do the work.

But I’ll tell you anyway,

Dilute alcohol will move into the bacterial cell wall slower due to the high osmotic pressure of the ethanol/water mix.

This mix will denature the proteins and destroy the cell wall as they slowly permeate into the cell, thereby inhibiting growth.

So any alcohol-water mixture less than 50% might be too dilute and may not even do anything. Anything above 80% might be too concentrated and can evaporate quickly.

I hope you learnt something new today!

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Also feel free to share any other scientific information on this topic. I still want to learn more 🤗.


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