Tea tree oil is a natural oil that's been proven to be as effective as benzoyl peroxide for treating acne. Both substances are antibacterial, but benzoyl peroxide can be overly irritating. Especially when combined with salicylic acid face wash, tea tree oil is a better alternative to a benzoyl peroxide regimen. Being a natural oil, it can also function as an effective moisturizer.
The study comparing tea tree oil to benzoyl peroxide can be found here: