To fully understand how oil works, you have to learn a bit about the structure of hair, itself. At its core is (in most hairs) the medulla, which is made up of proteins, explains Arun Nandagiri, president and owner of Bria Research Labs, a company that develops and tests haircare and skincare products. Surrounding it is the cortex, composed of long, spindly cells. And on the outside of each strand are the outer cuticle layers, which are like shingles on a roof. “They lie on top of the hair and protect it from damage,” Nandagiri says. Each hair usually has between six and eight of these protective layers.
When you damage hair—by using heat tools, chemically treating it, exposing it to environmental damage, or even brushing too aggressively—you can weaken chemical bonds in the hair and strip away cuticle layers, Nandagiri says, causing your hair to lose protein, its key building block. That’s where hair oils come in. Depending on their composition, they’ll help keep hair strong, block environmental damage, or give dull hair a healthy-looking shine. Here are a few ingredients to look for, depending on what your hair needs.
Oils That Strengthen Hair
Coconut oil helps keep hair healthy for two key reasons, chemically speaking: It’s a small, straight molecule, so it can slip between the cells of the cuticle layer, where it can get to the heart of your hair—and the cause of any damage. And it has a high affinity for the proteins that make up hair, meaning it helps them hold fast through shampooing, brushing, and other potential hazards, Nandagiri says. Since pure coconut oil can have a bit of a pungent smell, we reach for products that contain it like Ojon rare blend™ oil Rejuvenating Therapy. Its Tahitian coconut oil is infused with gardenias for a highly effective—and delightfully fragrant—blend.
Macadamia oil also has a small, straight structure, so it’s easily absorbed into hair where it can best protect and nourish strands. We like Macadamia Professional™ Healing Oil Treatment which is, as its name suggests, brimming with the nut’s nutrient-rich oil.
Oils That Protect Hair
Just like skin, your hair needs sun protection. Since you can’t apply SPF to your strands, antioxidant-packed oils that combat free radicals can be used to prevent UV damage. Hair treatments rich in argan oil, like Beauty Protector Protect & Oil, are naturally packed with vitamin E, a potent antioxidant, as well as fatty acids that protect hair. Argan oil doesn’t absorb as well into each strand as coconut or macadamia oil, but it gives hair a smooth, clean feeling while blocking those harmful rays, Nandagiri says.
Other antioxidant-rich ingredients have similar benefits. Roucou oil, the star ingredient in Davines OI/Oil Absolute Beautifying Potion, fights free radicals and boosts melanin production to keep strands healthy and maintain hair color.
Oils That Make Hair Shine
When you want your hair to shine bright like a diamond, Nandagiri says to look for an oil with a high refractive index, or, in other words, one with a superglossy finish. These ingredients sit on top of strands, bouncing back light to give hair loads of shine. But since they don’t soak into hair, they don’t do much to nourish it. That’s why they’re often combined with other, more rejuvenating oils, like the ones above, to bring the finial formula (and your finished style) extra radiance. Number4™ Fluoro5 Elixir Restore & Repair Oil adds silicone—which, while not an oil itself, is often added to hair oil for a bright shine and a smooth finish—to its blend of argan and sunflower oils, and Lulu Organics® Hair Oil mixes ubershiny olive oil into its botanical-based formula give hair a brilliant sheen.