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Hair oils have been used for centuries in Eastern countries such as India and Thailand. Castor oil therapy was said to be used as a beauty trick by Cleopatra.1 Ayurveda also describes in detail the practice of Shiroabhayanga, i.e., the massaging of oil onto the head using vegetable oils infused with essential oils and herbs, before taking a shower or before going to bed.
Hair oils have gained recent interest in the West for treating damaged hair.2 Indeed, hair oiling has emerged as a trend within the past 5-10 years, as evidenced by the increased number of product launches across geographies (see Figure 1). Especially in India, hair oils have almost completely penetrated the market (~95%),3 and the last five years of launches, in proportion with the entire hair care segment, indicate the resurgence of hair oil as a category (see Figure 2).
While hair oiling is well-established for hair care, research on its benefits for hair has not been reviewed. Thus, the objective of this two-part review is to gather the available scientific literature with respect to hair oil treatments and their effects on hair.
Part I, presented here, introduces oil types and examines their benefits for modifying the hair cuticle state. Properties within the scalp—i.e., the effects of actives and phytoconstituents of oils in the hair follicle—are out of scope for the present review. Part II, scheduled for July/August, will address internal or cortical changes to hair as a result of hair oiling.
Types of Hair Oil
Hair oils fit predominantly into two categories: vegetable oils, derived from plant seeds by crushing, pressing and subsequent refining; and mineral oil, a blend of polyunsaturated hydrocarbons obtained from petrochemical refining. Hair oil usage in a region typically correlates well with crop cultivation and the agricultural landscape of the region. For instance, argan (Moroccan) and olive oil are widely used in North Africa and Europe, while coconut oil and palm kernel oil (PKO) are predominant in South East Asia. Even within India, mustard oil is popular in the northern part, where mustard crops are cultivated, and coconut oil dominates the southern region in the top coconut-producing states.
For mineral oil, the most common grades used in the cosmetic industry are light liquid paraffin (LLP) and heavy liquid paraffin (HLP). It should be noted that other oils such as silicone, essential oils, etc., are also used as ingredients in hair care but are not categorized as hair oils. Silicone fluids, technically known as polydimethylsiloxanes, are used as hair conditioning agents in serums, conditioners and shampoos but are not used for head/scalp massage in the traditional way hair oils have been used. Similarly, essential oils are derived from natural plants to provide a specific aroma, e.g., lavender, patchouli, lemongrass, etc. These are used in small amounts to provide the requisite benefits of aroma and sensorial modification but are not typically used as the base for hair oils like mineral oil and vegetable oils are.
Marketed hair oils also are classified based on their composition (see Table 1).4 Most Type 1, or 100% vegetable-based oils, are considered sensorially heavy. They generally are viscous, feel sticky on the hands and weigh hair down. However, they are also known to provide the most functional and reparative benefits. Type 2 hair oils, based on 100% mineral oil, are generally lighter, non-sticky oils that provide a more sensorially pleasant feel both on the hands and hair, during and post-application. Type 3 hair oils, combining vegetable and mineral oils, fall between these two extremes and are designed to balance the contradiction of functionality and aesthetics.
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References
- Kiefer, E. (2019, Jul). Cleopatra used it as a beauty aid. Now castor oil is staging a cosmetics comeback. Available at: https://wapo.st/3egbXzb
- Rajani, T. (2020, Mar 16). Hair oils–Indian consumer–2020. Available at: https://store.mintel.com/report/hair-oils-indian-consumer-2020.
- Mintel (Accessed 2021, Jan 24). Data taken from Mintel Global New Products Database (GNPD). Available (with login) at: https://www.mintel.com/
- Consumer Voice (2011, Oct). The tress caressed-hair oil massage. Available at: https://consumeraffairs.nic.in/sites/default/files/file-uploads/ctocpas/hair%20oil-11.pdf.
