The chemistry of cleansing: why a facial oil removes sunscreen and makeup more completely than any foam

Why sunscreen and makeup cannot be fully removed with foam alone

The active ingredients in sunscreen filters — organic UV absorbers like octinoxate, avobenzone, and Korean filters like tinosorb M and S, as well as zinc oxide and titanium dioxide — are formulated to be water-resistant and to remain on the skin surface despite sweat and water contact. Makeup is formulated with similar durability. Both categories use lipophilic (oil-loving) components that bind to the skin surface and resist removal by water-based cleansers. A foam cleanser applied to a dry face emulsifies superficial oil but does not break down the film of SPF or makeup residue that has bonded to the skin surface throughout the day. The residue that remains — partially removed but not fully dissolved — accumulates in pores and over the skin surface, creating the congestion and dullness that appears after months of foam-only cleansing.

Like dissolves like: the chemistry behind oil-first cleansing

The principle "like dissolves like" from chemistry means that polar solvents (water, water-based cleansers) dissolve polar substances, and nonpolar solvents (oils) dissolve nonpolar substances. The oils, waxes and film-formers in sunscreen and makeup are predominantly nonpolar — they dissolve efficiently in oil and resist dissolution in water. A cleansing oil applied to dry skin dissolves the nonpolar components of sunscreen and makeup at the molecular level, releasing them from their bonding to the skin surface. The emulsifier system in most cleansing oils then allows the dissolved residue to be ringed away with water, preventing the cleansing oil itself from leaving a residue. This is why a good cleansing oil removes sunscreen and makeup more completely in 60 seconds than five minutes of foam cleansing would.

The skin benefits of oil-based first cleansing beyond residue removal

Beyond the mechanical benefit of complete SPF and makeup removal, a cleansing oil as the first step provides skin conditioning during the cleanse that foam-only cleansing cannot. The oils in a cleansing formula replace some of the natural lipids that warm water and surfactants inevitably remove from the skin surface during cleansing. A well-formulated cleansing oil leaves the skin barrier less stripped after cleansing than an equivalent foam-only approach, which translates directly into better response to the products applied after cleansing. Skin that is less dehydrated and lipid-depleted after cleansing absorbs toners, serums and moisturisers more effectively and shows more consistent hydration through the day.

Choosing a cleansing oil that emulsifies well without leaving residue

The key technical performance criterion for a cleansing oil is its emulsification system — the surfactant or emulsifier complex that allows it to be rinsed cleanly with water without leaving an oily film. Poor emulsification leaves a residue that clogs pores and undermines the point of the cleanse. A cleansing oil that turns milky white and removes cleanly with warm water (no post-rinse oily feel) has adequate emulsification. Some cleansing oils — particularly those marketed as "balm oils" or "cleansing balms" — require a separate rinse or a damp cloth for complete removal; these work well when used correctly but require more attention to ensure full removal. Standard emulsifying cleansing oils in pump format that fully rinse with water are the most user-error-resistant format.

The second cleanse: why the foam step is still necessary after an oil

An oil cleanse that has successfully removed sunscreen and makeup still leaves traces of the cleansing oil itself and its dissolved content on the skin. A second cleanse with a gentle, low-pH foam removes these traces and provides the clean skin surface that allows water-based actives to penetrate without any oil layer as a barrier. The second cleanse should use a significantly gentler surfactant than would be used in a foam-only approach — because the oil has already done the heavy lifting of dissolving the main residue, the foam step only needs to clean lightly, without the aggressiveness that would strip the skin. This gentleness in the second step is what makes the double cleanse, counterintuitively, less stripping than a single aggressive foam cleanse applied to a face still covered in sunscreen.