The LOC method (Liquid, Oil, Cream) and the LCO method (Liquid, Cream, Oil) are among the most widely discussed techniques in the curly and coily hair community. Both are layering approaches: apply water or a water-based product first, then follow with oil and cream in one order or the other. Proponents swear by one or the other. Critics call both overcomplicated.
The honest position sits between these: the scientific rationale for layering these product types is real and grounded in how hair holds and loses moisture. The specific question of whether oil before cream or cream before oil produces a measurably different outcome has never been tested in a controlled study. This piece explains what the science does and doesn't support.
Why hair struggles to hold moisture
Hair's ability to retain moisture depends on its lipid content and its structural integrity. The cuticle surface is coated with a lipid layer (primarily 18-methyleicosanoic acid, 18-MEA) that gives healthy hair its natural hydrophobicity. Beneath the cuticle, the lipid-rich cell membrane complex (CMC) regulates how water moves in and out of the fiber.
Research characterizing external and internal hair lipids found that removing the external lipid layer significantly reduced maximum water regain — the amount of moisture hair can hold. The external lipids contribute directly to the fiber's ability to retain moisture it has absorbed, not just its resistance to taking on water in the first place.[2]
When those lipids are depleted by chemical treatments, surfactant damage, or mechanical stress, hair becomes more permeable. Water enters more easily and also exits more easily. Hair that is structurally damaged or high in porosity absorbs water quickly during wetting and loses it quickly once away from the water source. This is the core problem the LOC and LCO approaches are designed to address.
Why moisture retention in hair is non-trivial
Hair's moisture behavior is not symmetrical. The rate at which hair absorbs water vapor is not the same as the rate at which it loses it — a property called hysteresis.
Research tracking moisture sorption and desorption isotherms across untreated and chemically treated hair found that chemically treated hair (particularly bleached hair) showed a larger "breaking of symmetry" between absorption and desorption than untreated hair. The authors proposed that chemical treatments create new hydrogen bonds that differ in strength from the original structure, changing the fiber's moisture dynamics in ways that persist after treatment.[3]
There are also two identified transition points in hair's moisture absorption: one around 30% relative humidity, where the inner hair structure opens and begins accommodating more water molecules, and another around 60% to 70% RH, associated with the glass transition of hair proteins. Both transitions affect the mechanical behavior of the fiber. Hair at high humidity is mechanically different from hair at low humidity, and this difference is more pronounced in damaged or high-porosity hair.[3]
This context matters for the LOC and LCO discussion: the goal isn't just to add moisture but to slow the rate at which moisture leaves, because once hair dries out, getting it rehydrated requires the full wetting process again.
The liquid step: water as the moisture source
Both LOC and LCO start with liquid. Water is the primary moisture source for hair — it is what hydrates the fiber and temporarily raises the cortex's water content. Water-based leave-in conditioners add both hydration and some conditioning agents (typically cationic compounds that bind to the hair surface and reduce friction).
The wetting step is when the hair is most receptive to absorption. High-porosity hair absorbs water particularly quickly. For highly porous or chemically damaged hair, research confirms that porosity increases with bleaching, physical damage, and routine wear — and that increased porosity corresponds directly to more variable and less controlled moisture exchange.[4]
Applying the liquid step to clean, well-conditioned hair (not freshly stripped by a harsh shampoo) maximizes how much moisture the hair can accept.
The oil step: slowing moisture loss
This is the step with the strongest direct scientific support.
A study using dynamic vapor sorption to measure moisture absorption and desorption in oil-treated versus untreated hair found that oil films on the hair surface significantly reduced the diffusion coefficient of water vapor — meaning water moved in and out of the fiber more slowly in oil-treated hair. Critically, this slowing applied in both directions: oil-treated hair absorbed humidity more slowly, and also lost moisture more slowly. The calculated effect was described by the researchers as similar to "moisturization" of the hair, in that it prolonged the time hair retained absorbed water.[1]
The same study found that the effect was attributable to both the oil film on the surface and to oil molecules that had penetrated into the CMC — both serve as diffusion barriers. Coconut oil-treated hair showed a higher moisture regain than mineral oil-treated hair, consistent with coconut oil's penetration advantage.[1] Heavier oils and butters that form a thicker surface film provide more resistance to water vapor diffusion.
The practical takeaway: oil applied over wet or damp hair creates a diffusion barrier that slows the rate at which the water the hair has just absorbed leaves the fiber. This is the core mechanism the LOC method is built on.
“The science behind each individual LOC and LCO step is solid. Oil films measurably slow moisture diffusion from hair. What hasn't been tested is whether the specific order between oil and cream makes a meaningful difference.”
The cream step: additional sealing and conditioning
The cream layer (which in practice can be a leave-in conditioner, curl cream, or styling butter) provides additional occlusion on top of the oil, plus whatever styling or conditioning actives the product contains.
Research on cuticle sealing as a strategy for protecting hair from surfactant-induced damage found that low-molecular-weight conditioning materials that deposit into the CMC and cuticle-adjacent regions could significantly reduce the porosity increase that washing creates. Cuticle sealing — physically occupying the pathways through which water and surfactants move in and out of the fiber — is a documented mechanism for preserving structural integrity.[5]
Heavy creams and butters perform a version of this: they provide an additional barrier layer above the oil, reduce friction between hair fibers, and contribute styling hold. For coily and kinky textures where moisture exits very rapidly and the fiber is structurally more complex, this additional sealing layer is particularly meaningful.
Does the order between oil and cream matter?
This is the central question separating LOC from LCO, and the honest answer is that no peer-reviewed study has directly tested whether applying oil before cream versus cream before oil produces a measurably different moisture outcome.
The reasoning cited by advocates of each order is plausible but untested at a clinical level:
The case for LOC (oil before cream): apply oil while the hair is still wet, so it seals the moisture in quickly before significant evaporation can occur. Cream on top provides an additional barrier and styling.
The case for LCO (cream before oil): apply cream first, while the hair is maximally wet and receptive, to allow water-soluble conditioning agents to penetrate. Then seal with oil on top, which has a better shot at effective coverage with a smooth surface below.
Both are reasonable arguments from first principles. Whether either leads to a measurably different outcome depends on factors — how quickly the specific hair type loses moisture, how fast a given oil spreads and absorbs, what's in the cream — that would vary significantly between individuals.
The porosity connection provides some practical guidance even without a direct study. High-porosity hair loses water very quickly after wetting. Getting oil on as fast as possible after the water step may matter more for high-porosity hair (LOC). Lower-porosity hair retains moisture more easily and may tolerate the cream-first order without the oil losing its moisture-sealing window (LCO). At very low porosity, the cuticle is already tight enough that layering order may matter less than the products themselves.
Who benefits most from these methods
The LOC and LCO approaches are designed for hair that has real difficulty retaining moisture: coily and kinky textures, high-porosity hair, chemically damaged hair, and hair in very dry environments. These are the cases where the problem the methods address is most acute.
For straight or wavy hair with intact porosity, a single well-formulated leave-in conditioner or light oil may provide all the moisture retention support needed without layering multiple product types. The methods add value proportionally to how severely the hair's moisture retention is impaired.
For anyone trying these approaches, starting simple is worth more than starting with strict adherence to one order over the other. Establish whether the three product types together produce better moisture retention than your current approach, then experiment with order if the results seem inconsistent.
ROOTS and routine building
ROOTS matches products to your specific hair profile — porosity, texture, and damage history all shape which conditioners, oils, and creams perform well for your hair. Whether a layering method suits your hair depends on those same variables. If your ROOTS quiz results show high porosity or significant damage, the moisture-retention logic behind LOC and LCO applies directly to your profile. Your matched products are the starting point; the layering method is a routine strategy you can build around them.