Water alone won’t kill germs – it’s the soap that counts. Flickr/CafeMama

“Despite decades of medical breakthroughs and growing health budgets, the simple act of washing our hands remains one of the most important things we can do to protect ourselves from disease.

“The principle of hand washing is simple: disease-causing germs (bacteria, viruses, fungi and parasites) get onto our hands and can cause infection if they’re transferred to the mouth, nose or eyes – depending on the type of organism, the dose and individual’s susceptibility.

“Cleaning your hands with soap or detergent can significantly reduce the load of these germs and the risk of passing on illness, particularly after using the toilet and before preparing food.

“But does it matter whether we use hot water or cold to wash our hands?

“The role of the water in hand washing is more controversial than the role of soap. Although you might wash off the dirt, and your hands may look clean enough, water alone isn’t that effective in removing germs, even when it’s hot.

“Germs grow rapidly in our bodies, which maintains a temperature of around 37°C. So the average hot tap temperature won’t kill disease-causing germs. Neither will water simply wash them away.

“Most germs are attached to the surface layer of the skin, which is formed from acidic fats, oils and cellular debris. To dislodge the germs, you have to dissolve this surface layer, then mechanically rub them off. This is why you need soap.

“And water is helpful in three aspects of cleaning.” Read this report from the conversation.edu.au here.