# Occlusives, Ranked by What They Actually Block Source: https://barrierbeautyguide.com/2026-11-11-occlusives-ranked-petrolatum-dimethicone-squalane.html November 11, 2026 *The moisturizer promises to lock in hydration. The ingredient list says dimethicone. The skin still feels tight by noon. The problem is not the product. The problem is that the occlusive in it blocks a fifth of the water loss, and the skin needed a twentieth of it blocked. Occlusives are not interchangeable, and the ranking between them is not close: petrolatum reduces transepidermal water loss by up to 98 percent, while dimethicone and squalane sit in the 20 to 30 percent range.* ## The ranking Petrolatum is first by a distance. Clinical evaporimeter studies consistently show pure white petrolatum reducing transepidermal water loss by over 98 percent, a figure no other cosmetic occlusive approaches. It is a purified mixture of semi-solid saturated hydrocarbons, and its molecules are too large to penetrate the stratum corneum, so it forms a semi-crystalline hydrophobic film on the surface. It does not integrate with skin lipids or alter ceramide architecture. It sits on top and blocks water from leaving, which is the whole mechanism, and the whole point. Dimethicone is second, and the gap is the story. A silicone film former, it reduces water loss by roughly 20 to 30 percent depending on viscosity and molecular weight. Squalane is in the same range, around 25 percent, and it is an emollient first and an occlusive second: it softens skin by filling intercellular gaps, but it does not seal the surface the way petrolatum does. Mineral oil sits near 20 to 30 percent as well. Lanolin and shea butter trail further behind. The ranking is stable across studies because the mechanism is physical, not chemical: the film either blocks the water or it does not, and the thickness and continuity of the film decide the number. ## Why petrolatum wins and when it loses Petrolatum wins because it is the most occlusive substance available at the cosmetic tier, and it wins on compromised skin most of all. Healthy skin loses 5 to 10 grams of water per square meter per hour. Compromised barrier skin, active eczema, post-procedure healing, winter dehydration, can reach 30 to 60. That is the skin that needs a 98 percent reduction, and the skin that gets the least from a 25 percent occlusive. A 2021 review in the Journal of the European Academy of Dermatology and Venereology found consistent overnight petrolatum application reduced water loss significantly within two weeks on barrier-compromised skin. It loses in three states, and all three are worth naming. Active sebum-rich acne with an inflammatory component, because occlusion traps heat and sweat and can worsen it. Skin prone to fungal acne, because Malassezia thrives in warm, occluded environments. And skin with a retinoid or acid underneath, because occlusion amplifies the penetration of everything applied before it, which raises both efficacy and irritation risk. The comedogenicity worry, by contrast, is unfounded at the molecular level: petrolatum's particle size prevents follicular penetration, and clinical studies do not associate it with comedone formation. Kligman's original rabbit-ear studies graded purified petrolatum at the lowest possible score; the crude petroleum derivatives that caused problems were unrefined and carried residual aromatic hydrocarbons. ## Matching the occlusive to the skin Dry, compromised, winter skin gets petrolatum, as the last step, at night, over a humectant. The order matters: occlusives must be applied after humectant and hydrating layers, not before, because applied first they block subsequent ingredient penetration. Oily and acne-prone skin gets dimethicone or squalane, which offer meaningful water-loss reduction with better cosmetic compatibility and no trapped heat. Post-procedure skin gets petrolatum, because it is still the ingredient of choice for wound care and healing support. The choice is not about which occlusive is best in the abstract. It is about how much water the skin is losing, and the number on the ranking decides it. For the slugging version of this, see [when slugging helps and when it traps trouble](2026-11-09-slugging-petrolatum-barrier-repair-when-it-helps.md), and for the measurement behind the ranking, [what transepidermal water loss actually measures](2026-11-08-tewl-what-transepidermal-water-loss-measures.md). ## Frequently asked questions ### How much does petrolatum reduce water loss? Up to 98 percent, in clinical evaporimeter studies of pure white petrolatum as a neat film. Emulsified formulations with 5 to 10 percent petrolatum achieve 50 to 70 percent, and water-in-oil formulas reach 70 to 90 percent. The neat film is the number to remember. ### Is petrolatum comedogenic? No, at the molecular level. Its hydrocarbon molecules are too large to enter follicular ostia, and clinical studies do not associate purified petrolatum with comedone formation. The comedogenicity worry comes from Kligman's rabbit-ear tests on crude, unrefined petroleum derivatives, not on USP-grade petrolatum. ### Can I use petrolatum over a retinoid? You can, but occlusion amplifies the penetration of everything underneath, which raises both efficacy and irritation risk. If the retinoid already irritates, petrolatum over it will make the irritation worse. Buffer first, or skip the occlusive on retinoid nights. ### Does slugging repair the barrier, or just protect it? It protects it. Petrolatum creates favorable conditions for barrier recovery by maintaining hydration, but ceramide and lipid synthesis happens independently inside keratinocytes. Slugging does not synthesize ceramides. It buys the skin the moisture it needs to do the work itself.