Macadamia oil is commonly used in hair care products and treatments, and its popularity is supported by some scientific rationale, though robust human clinical evidence is limited. The oil is rich in monounsaturated fatty acids, particularly oleic acid and palmitoleic acid, which are known for their emollient and moisturizing properties. Laboratory analyses and in vitro studies have shown that these fatty acids can help improve hair softness, manageability, and may reduce frizz by coating the hair shaft and reducing water loss. Additionally, macadamia oil contains antioxidants such as tocopherols (vitamin E), which may help protect hair from oxidative damage caused by environmental factors.

While there are no large-scale clinical trials specifically on macadamia oil's direct effects on hair growth or scalp health, the oil’s composition is similar to sebum, the natural oil produced by the scalp, which suggests it may be well-tolerated and beneficial for moisturizing and conditioning hair. Most evidence comes from in vitro studies, animal research, and extrapolation from the known properties of fatty acids and tocopherols. Traditional and anecdotal use also supports its application for improving hair texture and shine, but the scientific rating remains moderate due to the lack of direct human studies.