Petroleum jelly (petrolatum) is not comedogenic, meaning it does not clog pores or create the plugs that lead to acne. This has been directly tested in both animal and human skin studies. However, the answer comes with a practical nuance: while petrolatum itself doesn’t block pores, the way you use it and the grade of product you choose can still contribute to breakouts in certain skin types.
What the Research Actually Shows
The most direct study on this question, published by dermatologist Albert Kligman, tested petrolatum on both rabbit ears (a standard model for comedogenicity testing) and human skin. The conclusion was unambiguous: petrolatum is not comedogenic in rabbits or humans. Kligman went further, arguing that the common advice for acne patients to seek oil-free skin care products “has no scientific merit” and that cosmetics are an unlikely cause of the relatively high prevalence of adult female acne.
The reason petrolatum doesn’t clog pores comes down to its molecular size. Its hydrocarbon molecules are too large to penetrate into the pore lining where comedones (the technical term for clogged pores) actually form. Instead, petrolatum sits on the skin’s surface as an occlusive layer, trapping moisture underneath. It acts more like a physical shield than something that absorbs into your skin.
Why It Can Still Cause Breakouts
If petrolatum doesn’t clog pores, why do some people break out after using it? The distinction matters: something can trigger pimples without being comedogenic in the strict sense. Petrolatum’s occlusive barrier traps everything underneath it, including sweat, bacteria, and any other products you’ve applied. If your skin is already oily or if you layer it over pore-clogging ingredients, that sealed environment can encourage the conditions bacteria thrive in.
The American Academy of Dermatology recommends avoiding petroleum jelly on your face if you are acne-prone, as it may cause breakouts in some people. This isn’t because of comedogenicity but because of the trapping effect. For someone with dry or normal skin, that same occlusive quality is a benefit. For someone producing excess oil, it can tip the balance toward irritation and blemishes.
Product Purity Makes a Difference
Not all petrolatum is the same. The product exists in several grades, and the refining process determines what else comes along with it. USP-grade white petrolatum (the kind sold as Vaseline and similar pharmacy brands) is highly refined and meets pharmaceutical standards. Industrial or less-refined grades can contain impurities, including polycyclic aromatic hydrocarbons, which are byproducts of petroleum processing.
Some amber-colored petrolatums contain trace amounts of these compounds, around 6 parts per million. While testing on mouse skin produced no evidence of tumor activity at those levels, these impurities are one reason to stick with cosmetic or pharmaceutical-grade products rather than anything industrial. If you’re buying petroleum jelly from a standard drugstore, you’re almost certainly getting USP-grade white petrolatum, which is the version that’s been tested and found safe for skin use.
Using Petrolatum on Acne-Prone Skin
“Slugging,” the practice of applying a layer of petroleum jelly as the last step in a nighttime skincare routine, has become popular for its moisturizing effects. For most skin types, it works well. But if you have oily or acne-prone skin, there are a few practical guidelines worth following.
If your skin is combination type, with both oily and dry zones, you can apply petrolatum only to the dry areas while avoiding your T-zone or other breakout-prone spots. This prevents trapping excess oil and bacteria in areas already prone to congestion while still getting the hydration benefits where you need them. Thorough cleansing before application is essential. Petrolatum locks in whatever is on your skin, so applying it over dirty or heavily layered skin increases the chance of problems.
People with oily skin who want to try slugging should patch-test on a small area for a few nights before committing to full-face application. If you notice small pimples forming, that’s the occlusive effect at work rather than true comedogenicity, and it means the technique isn’t a good fit for your skin. Discontinue if irritation develops.
The Bottom Line on Comedogenicity Ratings
Petrolatum scores a 0 on most comedogenicity scales, which range from 0 (won’t clog pores) to 5 (highly likely to clog pores). This rating is based on controlled testing where the ingredient is applied directly to skin and pore plugs are measured. By that standard, petroleum jelly is one of the least comedogenic moisturizing ingredients available.
The confusion comes from conflating “comedogenic” with “causes acne.” These aren’t identical. Acne is driven by multiple factors: excess oil production, bacterial growth, inflammation, and yes, pore clogging. Petrolatum doesn’t contribute to the pore-clogging piece, but its occlusive nature can aggravate the other factors in people whose skin is already primed for breakouts. For the majority of people, including those healing dry or damaged skin, it remains one of the safest and most effective barrier products available.