A century-old antiseptic made from coal tar and used to treat wounds and sleeping sickness in World War I Australian soldiers has been found to help the body fight off viral infections, including the common cold.

Acriflavine antiseptic is a brown or orange powder that is mixed with water to wash out wounds and treat abrasions.

In World War I and World War II it was used to treat everything from open wounds and bladder infections to gonorrhoea. It was also used to kill the parasite that causes sleeping sickness. But it has never been clear how it worked – until now.

Molecular biologists Michael Gantier and Genevieve Pepin from Melbourne's Hudson Institute of Medical Research have established that the antiseptic attaches to the DNA of the patient, which sparks the body's immune system into action.