What risks come with sharing a toothbrush? Apart from spreading tooth decay and gum problems, sharing a toothbrush can pass on viruses and infections. These can include colds, flu, cold sores, and even more serious illnesses like hepatitis. A toothbrush can hold blood from your gums as well as saliva, so the risks are higher than many people realise. Quote attribution: Dr Nigel Carter Manage Cookie Preferences