Handwashing with soap is significantly more effective than using water alone because of how soap interacts with the oils and microbes on our hands. Water alone cannot break down the natural oils and lipids on our skin, which often trap germs, dirt, and other contaminants. As a result, simply rinsing with water might remove some debris, but it leaves behind many pathogens.

Soap, however, contains surfactants-substances that reduce the surface tension of water and help lift oils and grease from surfaces. These surfactants have hydrophobic (oil-attracting) and hydrophilic (water-attracting) ends. When you wash your hands with soap and water, the surfactants latch onto the oils (and the germs within those oils) with their hydrophobic ends. The hydrophilic ends then bind with water, allowing the whole structure-called a micelle-to be rinsed off the skin.

Moreover, soap is effective against viruses, especially enveloped viruses like the flu and coronavirus. These viruses are surrounded by a lipid membrane that soap can break down, rendering them inactive.

Scientific studies have shown that proper handwashing with soap can remove more than 90% of pathogens, whereas washing with water alone removes only a fraction. This makes a huge difference in preventing illnesses like diarrhea, colds, and respiratory infections.

Additionally, soap helps ensure a more thorough scrubbing action, as its lather encourages people to rub all areas of their hands, including between fingers and under nails. This mechanical action further assists in dislodging germs.

Soap is crucial for effective hand hygiene because it removes oils that trap germs and inactivates many types of harmful microbes. Handwashing with soap is a simple, accessible, and powerful method to reduce the spread of infections.