White oil is a highly refined petroleum-based mineral oil that has been stripped of nearly all aromatic hydrocarbons, sulfur compounds, and other impurities until it becomes colorless, odorless, and chemically inert. Depending on the grade, it shows up in baby oil, pharmaceutical laxatives, food-processing equipment, and agricultural pest sprays. The level of refining is what separates white oil from ordinary mineral oil, and that distinction determines both its safety profile and its regulatory approval for different uses.
How White Oil Is Made
All white oil starts as crude petroleum. During refining, the crude is distilled under vacuum to produce base oil fractions, which still contain a complex mixture of hydrocarbons, including polycyclic aromatic compounds that are linked to cancer risk when exposure is chronic and dermal. The refining challenge is to remove those aromatic compounds while keeping the saturated hydrocarbons that give the oil its useful lubricating and moisturizing properties.
Three main industrial processes accomplish this. Solvent extraction uses a selective solvent to pull aromatic compounds out of the base oil. Catalytic hydrotreating forces hydrogen through the oil under high pressure and temperature, converting aromatics into saturated hydrocarbons. Hydrocracking goes further, breaking down and restructuring the molecular chains. Modern white oil production typically uses severe hydrotreating or hydrocracking to reach the extreme purity levels required for pharmaceutical and food-grade designations.
The result is an oil composed almost entirely of mineral oil saturated hydrocarbons (MOSH), with only trace amounts of mineral oil aromatic hydrocarbons (MOAH). The ratio between these two fractions is the key quality metric that determines what the oil can legally be used for and how safe it is considered for human contact.
Grades and How They Differ
White oils are broadly grouped into three tiers based on purity, and each tier maps to different regulatory approvals and end uses.
- Technical grade: The least refined of the white oils, used in industrial applications like metalworking, textile processing, and equipment lubrication where skin or food contact is not intended. Technical-grade white oil has undergone significant purification compared to ordinary base oils but still contains somewhat higher residual aromatic levels.
- Food grade: Meets specific regulatory standards, such as FDA 21 CFR 172.878 and 178.3620 in the United States, that limit aromatic content to extremely low levels. Food-grade white oil is approved for use as a release agent on baking pans, a protective coating on fresh produce, and a processing lubricant in food machinery where incidental contact may occur.
- Pharmaceutical grade: The most stringently refined tier. This oil must meet the monograph specifications of pharmacopeias like the United States Pharmacopeia (USP) or British Pharmacopoeia (BP), which set strict limits on UV absorbance (a proxy for aromatic content), viscosity range, and other purity markers. Pharmaceutical-grade white oil is what you find in medicinal products, baby oil, and high-end cosmetics.
Research examining white oil performance has specifically distinguished between pharmaceutical and technical grades, confirming that the two behave differently even in non-medical contexts such as oxidation stability testing.1J-STAGE / Journal of Oleo Science. Antioxidation Performance of Essential Oils of Herbs and Spices in White Mineral Oils This is not just a regulatory formality: the grade genuinely changes the chemical composition of the product.
The viscosity of white oil also varies widely across grades and products. You’ll see everything from thin, watery oils used in cosmetic sprays to thick, viscous oils used as pharmaceutical laxatives. Commercial white oils range from roughly 10 to over 70 centistokes at 40°C, and the viscosity you need depends entirely on the application.
Skincare and Cosmetic Applications
White oil, typically pharmaceutical grade, is one of the most widely used ingredients in skincare. It works as an occlusive moisturizer: it sits on the surface of the skin and forms a barrier that slows down the evaporation of water from the skin’s outer layer. Controlled testing has shown that mineral oil improves skin barrier function and reduces water loss better than some other common emollients.2PubMed. A review on the extensive skin benefits of mineral oil
A common concern is whether mineral oil clogs pores. Earlier studies that found pore-clogging effects used crude or poorly refined mineral oils, not the pharmaceutical-grade white oil found in modern skincare products. The distinction matters because the impurities in lower-grade oils are what tends to cause problems, not the purified saturated hydrocarbons themselves. If your moisturizer or baby oil contains USP-grade mineral oil, the comedogenicity concern is largely outdated.
Another persistent worry is that mineral oil “absorbs into the body” and accumulates in organs. The evidence goes firmly against this. Multiple studies have found that mineral oils and waxes penetrate the skin very poorly. They are mainly adsorbed onto the outermost dead layer of skin, with no evidence that they reach the bloodstream in any meaningful amount.3PubMed. Mineral oils and waxes in cosmetics: an overview mainly based on the current European regulations and the safety profile of these compounds Modeling of dermal penetration rates supports this conclusion, with predicted skin absorption values being extremely low across all mineral oil and wax types examined.4Toxicology Letters. Review of data on the dermal penetration of mineral oils and waxes used in cosmetic applications
None of this means white oil in skincare is for everyone. Some people find occlusive products uncomfortable, especially in humid climates where the barrier effect can make skin feel greasy or heavy. And while pure mineral oil itself is well-tolerated, fragrances or other additives in commercial baby oil or body oil products can cause irritation in sensitive individuals. The issue there is the formulation, not the white oil base.
Pharmaceutical and Laxative Use
The most established medical use of white oil is as a lubricant laxative. When taken orally at doses of 15 to 45 mL, pharmaceutical-grade mineral oil coats the bowel wall and stool with a waterproof film. This film slows down water absorption in the colon, keeping the stool soft and easier to pass. The effect is purely mechanical: unlike stimulant laxatives, mineral oil does not directly trigger intestinal contractions. Any change in colonic movement is a secondary result of the softer stool mass.5PubMed Central. Mineral oil: safety and use as placebo in REDUCE-IT and other clinical studies
White oil is also used as a base for certain topical pharmaceutical preparations, wound-care ointments, and as a carrier in some ophthalmic lubricants. In clinical research, mineral oil capsules have served as placebos in studies of fish oil supplements, though this practice has drawn debate over whether mineral oil is truly inert enough for that role.
One practical concern worth knowing about: regular oral use of mineral oil at laxative doses can reduce the absorption of fat-soluble vitamins (A, D, E, and K) from the gut. These vitamins dissolve into the oil coating and pass through without being absorbed. For occasional constipation, this is not a real problem. For people who use mineral oil daily as a laxative over weeks or months, it can lead to deficiencies, and a conversation with a doctor makes sense before committing to that routine.
Food Contact and the MOSH/MOAH Question
Food-grade white oil has a long history in food processing, but a growing body of research has raised questions about low-level exposure to mineral oil hydrocarbons through the food supply. The concern centers on those two families of chemicals mentioned earlier: MOSH and MOAH.
MOSH are the saturated hydrocarbons that make up the bulk of white oil. They accumulate in human tissues to some degree, but the health significance of that accumulation remains debated. Some rat strains develop liver inflammation when exposed to high levels of MOSH containing wax components, but the European Food Safety Authority (EFSA) concluded in a 2023 risk assessment that the rat strain showing these effects (Fischer 344) is not a good model for humans, because its liver handles wax components differently than human livers do. EFSA set a reference point for MOSH from a white mineral oil free of wax components at 236 mg per kilogram of body weight per day, corresponding to the highest dose tested without adverse effects.6PubMed Central. Update of the risk assessment of mineral oil hydrocarbons in food
MOAH are the more worrying fraction. Aromatic hydrocarbons with three or more rings are associated with genotoxicity and cancer risk. EFSA used a much lower reference point for this subfraction, just 0.49 mg per kilogram of body weight per day, derived from safety data on polycyclic aromatic hydrocarbons.6PubMed Central. Update of the risk assessment of mineral oil hydrocarbons in food The gap between those two reference points, roughly a 500-fold difference, neatly illustrates why the saturated and aromatic fractions of mineral oil cannot be lumped together when talking about safety.
For properly manufactured food-grade white oil, MOAH levels should be negligibly low. The more practical concern involves contamination during food processing or migration from recycled paper and cardboard packaging, where printing inks and adhesives can introduce mineral oil hydrocarbons that were never intended to contact food. This is a packaging-science problem more than a white-oil problem, but it has driven tighter analytical testing requirements across the food industry in both the EU and the United States.
Agricultural and Industrial Applications
Horticultural oil, sometimes called spray oil, is a refined petroleum oil used in agriculture to control insect pests on fruit trees, ornamental plants, and greenhouse crops. These products work by coating the pest’s body and blocking its breathing pores, cutting off gas exchange and essentially suffocating the insect. The effectiveness depends partly on the pest: the waxy cover of armored scale insects can resist penetration by polar soaps, while the more polar integument of soft-bodied scales can impede the infiltration of the oil itself.7HortTechnology. Efficacy of Horticultural Oil and Insecticidal Soap against Selected Armored and Soft Scales
Horticultural oils are generally classified as either dormant oils (applied in winter when plants are leafless, at higher concentrations) or summer oils (applied during the growing season at lower concentrations to avoid damaging foliage). Modern formulations are highly refined to minimize phytotoxicity. The unsulfonated residue (UR) value is the standard measure of purity here: a UR above 92% is typical for horticultural grades, meaning at least 92% of the oil resists reaction with sulfuric acid. Higher UR values mean fewer impurities that could burn plant tissue in sunlight.
On the industrial side, white oil serves as a plasticizer in rubber and plastics manufacturing, as a dust suppressant, as a textile lubricant, and in the production of printing inks. Technical-grade white oil is sufficient for most of these roles, though some food-packaging applications, like polystyrene food trays, require food-grade certification because the oil can migrate out of the material and into whatever food sits on it.
Inhalation and Aspiration Risks
The safety profile of white oil changes dramatically when it enters the lungs. Swallowing pharmaceutical-grade mineral oil is generally safe for most adults at recommended doses, but inhaling or aspirating it can cause a rare condition called exogenous lipoid pneumonia, an inflammatory reaction triggered when oil droplets reach lung tissue.8PubMed Central. Exogenous Lipoid Pneumonia Complicated by Mineral Oil Aspiration in a Patient With Chronic Constipation: A Case Report and Review The condition is frequently misdiagnosed because it mimics bacterial pneumonia or even lung cancer on imaging.
The people most at risk are elderly individuals who use mineral oil as an oral laxative and inadvertently aspirate small amounts into the lungs, particularly when lying down or when swallowing is impaired. Young children and people with neurological conditions that affect swallowing are also vulnerable. For this reason, many guidelines recommend against giving mineral oil orally to children under three, elderly patients with swallowing difficulties, or anyone who is bedridden.
In occupational settings, workers exposed to mineral oil mist from metalworking or machining equipment face a different kind of inhalation concern. Chronic exposure to airborne oil droplets can irritate the respiratory tract over time. Prior to updated recommendations, the standard occupational exposure limit was 5 mg per cubic meter as a time-weighted average, with a short-term limit of 10 mg per cubic meter.9PubMed Central. The Occupational Exposure Limit for Fluid Aerosol Generated in Metalworking Operations: Limitations and Recommendations The degree of refining matters here as well: mist from highly refined white oil carries far fewer aromatic contaminants than mist from conventional cutting fluids, which is one reason the industry has moved toward better-refined metalworking oils.
How White Oil Purity Is Verified
Given that the safety of white oil depends almost entirely on how well aromatic compounds have been removed, analytical testing of the finished product is critical. Traditional quality control relied on UV absorbance measurements, which give a rough sense of aromatic content. Pharmacopeial tests for white oil essentially shine UV light through the oil at specific wavelengths and measure how much is absorbed: high absorption means more aromatics, which means the oil fails the spec. This approach works well enough for high-concentration aromatics but struggles at the trace levels that modern regulations demand.
More sophisticated methods have emerged. One approach that has gained traction uses silver-ion liquid chromatography coupled with two-dimensional gas chromatography. The silver-based column separates hydrocarbons according to their degree of aromaticity, since aromatic molecules bind to silver ions more strongly than saturated ones, and the second chromatographic dimension provides detailed resolution. Detection can be done by flame ionization or by vacuum ultraviolet spectroscopy, which provides structural information about the molecules and helps confirm whether trace peaks are truly aromatic or merely unsaturated. This eliminates some of the ambiguity that plagued older methods and removes the need for arbitrary cutoff markers between the MOSH and MOAH fractions.10LCGC International. Analysis of White Oils Using AgLC×GC
These analytical advances matter because regulatory agencies, particularly in Europe, have been pushing toward lower acceptable limits for MOAH in food-contact materials. A white oil that passed muster a decade ago might not meet tomorrow’s threshold, and manufacturers need methods sensitive enough to detect aromatics at parts-per-million levels in a background of overwhelmingly saturated hydrocarbons. The analytical challenge is a bit like spotting a handful of colored marbles in a swimming pool full of clear ones: you need a separation technique that sorts by the right property and a detector sensitive enough to register what you have sorted.