Though most often recommended for oily hair due to their astringent qualities, a small amount of tea tree or rosemary essential oil can be helpful for maintaining freshness. Rosemary also boosts shine, and one study found that it promotes hair growth. (Where to buy tea tree, where to buy rosemary) Lavender is one of my favorite nourishing oils for normal/dry hair. (Where to buy lavender essential oil) Vanilla resin just smells amazing, especially with the light coconut scent of this conditioner. It doesn’t have any properties that would assist in keeping the conditioner fresh, though, so I would pair it with another oil. (Here’s what I use) I also love this anti-age blend because it smells like honeysuckle. (It’s pricey, though!)