Soap or Sanitisers – what’s the difference?

The first record of a soap-like substance is from around 2800 BCE, by the Babylonians and Egyptians, who made soap from a mixture of oils, ashes and alkali salts.

Soap or Sanitisers – what’s the difference?

The first record of a soap-like substance is from around 2800 BCE, by the Babylonians and Egyptians, who made soap from a mixture of oils, ashes and alkali salts. We have come a long way since then but the basic recipe for making bar soap remains essentially the same.

Soap is made from a chemical reaction in which the building blocks of fats and oils (triglycerides) react with an alkali (e.g. lye) to form bar soap. Liquid soaps were invented in the 1970s and soap now comes in many different forms with varying ingredients.

Soap is important because it is the simplest way of destroying bacteria and viruses that can transmit disease. It works because it has a hybrid structure with a hydrophilic head (bonds with water) and a hydrophobic tail (bonds with oils).

Many bacteria and viruses have a lipid (oil) membrane as an outer layer. When hands are washed with soap and water, the hydrophobic tails ‘wedge’ themselves into the membrane and break it apart (please note some organisms are resistant to this action). These fragments are then trapped in soap bubbles (micelles), which are washed away in the water.

Soap or Sanitisers

Vigorous scrubbing with soap and water for 20-30 seconds is an effective means of removing micro-organisms from the skin.

It is important to note that liquid soap differs from hand sanitisers, which traditionally carry a high percentage of ethanol (often more than 70 per cent) as their main method of action. They destabilise membrane layers but cannot easily remove the bacteria/viruses from the skin. An alcohol-based sanitiser used for 15 seconds is a good option if soap and water are unavailable.

The use of soap or sanitisers for handwashing has been shown to be effective for reducing the risk of gastrointestinal and respiratory infection. Use soap or sanitisers to reduce your risk of infection!

Reference: ASK AN EXPERT – Townsville Bulletin – TB, 5/6/2020

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About the author

Dr Roy is a medical practitioner with over 25 years’ experience working in tertiary and primary care. He previously trained and worked in Victoria but currently resides in tropical north Queensland, teaching the next generation of doctors.  He is passionate about education, for health care profes ... more