When it comes to curly hair, oils are a major key. In fact, almost every single complaint you have about your curls can be resolved with the right oil: from frizz to lack of shine, brittle hair, and even split ends. Curly hair tends to hold less hydration than straight hair. This lack of hydration causes frizz, making hair look dull (read: no shine). A lack of hydration also causes brittle hair, which leads to more split ends. All of this stems from your curl pattern, not a natural inclination that you have for drier hair. The oils produced on your scalp — a.k.a. sebum — are what hydrate hair, adding shine, decreasing frizz, and giving it strength.
For those with straight hair, those oils slip down the shaft rather easily. Brushes help pull oils from the scalp down, and distributes them throughout the hair. Since it's difficult for oils to slide down a spiral or coil, this is why curly hair textures are drier than straight versions. But you don't need a brush or even your natural oils to get a shiny, frizz-free style. All you need is the right hair oil. "They're a wonderful way to moisturize the hair," says Sarah Stevens, a curly-hair vlogger for WaterLily716. "And, they are totally natural. Most pure oils are easy to remove from the hair and they don't contain synthetic ingredients."
FYI, there are two main types of oils: sealing and moisturizing. Sealing oils (think jojoba) seal in moisture, meaning that you'll need to apply water or conditioner to your hair beforehand for them to really work. Moisturizing oils (we're talking coconut, olive, or avocado) are heavier than sealing oils and can be used alone to moisturize the hair. Sealing and moisturizing oils are meant to be used at different times — one after a shower, for instance, and the other during a deep-conditioning treatment — and each applied in different ways. You can use an oil to hydrate your scalp, encourage hair growth via massaging, reduce split ends, add in your conditioner, apply a heat treatment (with a heavier oil) — the options go on and on.