We are all aware that soap works to cut through grease in order to produce a cleaner, more sanitised result – but why? How does soap work and what is the science behind it?

Soap is a very effective hand and body cleanser. However, not only does it cleanse it also sanitises by destroying bacteria and viruses. Read on to discover why soap works.

How Soap Works

Oil & Water Doesn’t Mix

The purpose of washing is to remove the outer layer of oils and fats that harbour germs and rinse them away from the skin. Oils and fats are known as ‘nonpolar’ compounds, which means they cannot be dissolved by water alone. This can only be done if we wash with something that can attach to fat molecules. Soap works by mixing with both water and with oil. 


When greasy dirt or oil is mixed with soapy water, the soap molecules arrange themselves into tiny clusters called micelles. The water-loving (hydrophilic) part of the soap molecules sticks to the water and points outwards, forming the outer surface of the micelle. The oil-loving (hydrophobic) parts stick to the oil and trap oil in the centre. The soap molecules arrange themselves to become a barrier, trapping the oil in the centre. As the soapy water is rinsed away the greasy dirt goes along with it. 

Soap Washes Everything

Therefore, when you wash with soap and water the soap molecules grab on to the fat molecules and pulls them off the skin into the rinse water. When your rinse the skin the fat and germs are removed from the skin. Therefore, the main reason why soap works to cleanse and sanitise is it literally washes everything off the skin.

Washing with Hot vs. Cold Water

Ever wonder why it is easier to clean dirt and grease in hotrather than cold water? It is because the fats and oils soften or melt in hot water, which allows them to attach more readily to the hydrophobic end of the soap molecule. In turn, that makes it easier to rinse away.

Find out more about why soap works here.