Tea tree is a famous natural antiseptic and effective against bacteria. Also a handy oil if you use washable cloth nappies, as it makes a valuable disinfectant.
Directions for use: Dilute 5 drops of essential oil in 10ml of carrier oil (such as peach, sweet almond or apricot) for massage. Use up to 10 drops in a bath. Use up to 1 teaspoon per litre of water as a disinfectant for nappy buckets.