As I mentioned a moment ago, you might want to add tea tree oil to your hand sanitizer. This is because the essential oil has antimicrobial properties (and smells nice). There’s some evidence from a 2013 study that tea tree oil could help stop the spread of influenza, but there’s far more evidence to support the use of isopropyl alcohol or ethanol. Before you turn to tea tree oil alone as your natural hand sanitizer of choice, you might want to consider that tea tree oil can trigger allergic reactions in some people. Also, not all tea tree oil is the real deal, with some ‘essential oils’ diluted before sale. This would seriously affect any antimicrobial activity, while creating a false sense of security. Cost is also a consideration, with alcohol a cheap and effective antimicrobial compared to tea tree oil.