mineral
Evidence tier: strong
Petroleum jelly does not feed or heal skin. It forms a seal that stops water escaping, cutting water loss by up to about 98%, which lets the skin rehydrate and become flexible again instead of cracking. Because it seals in whatever is already there, put it on damp skin, not dry. Never put it inside your nose.
Purely physical occlusion, with no pharmacological activity whatsoever, which is precisely why it is so reliable. Petrolatum forms a semi occlusive hydrophobic film over the stratum corneum that reduces transepidermal water loss by up to approximately 98%, the highest of any commonly available emollient. That trapped water rehydrates the corneocyte layer, restoring flexibility to keratin that had become rigid and prone to fissuring. There is also evidence that occlusion itself signals the skin to upregulate endogenous lipid synthesis, so it does more than simply hold water in. Because the mechanism is occlusive rather than humectant, the timing of application is functionally part of the mechanism: applied to damp skin it seals in the water already present, while applied to dry skin it seals in nothing. In combination products, urea contributes separately as both a humectant and, at higher concentrations, a keratolytic that disrupts hydrogen bonding between keratin filaments to soften and thin callus, and glycerine contributes as a humectant.
One of the best evidenced and least glamorous ingredients available. A randomised, double blind, placebo controlled trial of a urea, glycerine and petrolatum containing moisturiser demonstrated significant healing of deep foot fissures at both 2 and 4 weeks (PMID 28627029), and a comparative study found urea 5% formulations superior to glycerol based emollients on skin hydration measures (PMID 25851453). Petrolatum's occlusive performance, reducing transepidermal water loss by up to around 98%, is well characterised and is the benchmark against which other emollients are measured. It is also the reference standard for low irritancy in patch testing, which is an unusual and meaningful credential. The evidence tier is strong, which almost nothing else in this expansion earns. Two honest framing points. First, the effect is entirely physical: petrolatum does not heal, nourish or repair in any biological sense, it prevents water leaving so the skin can do those things itself. Second, and worth stating in any content where a herbal alternative might be assumed superior, olive oil has been found in comparative study to DAMAGE the skin barrier and cause erythema, attributed to its oleic acid content disrupting the intercellular lipid lamellae. The cheap petroleum derived product outperforms the natural sounding one, and saying so is more useful than the reverse.
Topical, applied liberally. For cracked heels, a generous layer over the whole heel applied to damp skin after soaking, covered with cotton socks overnight, nightly for the first 2 weeks then 2 to 3 times weekly. For hand and general dry skin, applied as often as needed, typically after every wash.
The single most important application note is that it goes onto DAMP skin, not dry. Petrolatum seals in whatever water is already present, so applying it after a soak or immediately after washing while the skin is still slightly damp is functionally part of the mechanism rather than a refinement of it. Thicker is better: ointments contain more oil and less water than creams, and creams more than lotions, so a product that pumps easily out of a bottle is generally too thin for a fissure. Occlusion under cotton socks or gloves extends contact time dramatically compared with an application that gets washed off within minutes. If urea is being used alongside for thick callus, apply the urea first and allow it to absorb, then the petrolatum over the top. Urea stings sharply on an open fissure, so close the surface with petrolatum alone first.
Onset: ~3 days
Among the safest topical substances in common use, with two specific hazards that matter a great deal in the contexts where they apply. FIRST AND MOST IMPORTANT: NEVER APPLY PETROLATUM INSIDE THE NOSE. Inhaled or aspirated petrolatum causes lipoid pneumonia, a serious and sometimes chronic lung condition, and applying it to the nasal lining for dryness or nosebleeds is a common and genuinely harmful piece of folk advice. SECOND: paraffin based emollients are FLAMMABLE when absorbed into fabric. Clothing, bedding, dressings and gloves soaked in emollient can ignite and burn fiercely, and this is the subject of a formal MHRA safety alert in the UK. Keep away from open flames, gas hobs, candles and cigarettes, and wash impregnated fabric regularly. Beyond these, petrolatum is non comedogenic in the classical sense but can occlude an already infected area, so do not apply over infected, weeping or crusted skin, which needs treatment rather than sealing. It is extremely slippery, which is a real fall risk when applied to feet, so apply while seated and put socks on before standing. Cosmetic and pharmaceutical grade petrolatum is highly refined and does not carry the polycyclic aromatic hydrocarbon concerns associated with unrefined petroleum fractions.
Pregnancy: safe
Breastfeeding: safe
Introduced commercially in the 1870s and in continuous use since, making it one of the oldest continuously marketed topical products. It has no herbal or traditional medicine lineage, and this record does not manufacture one.
Active compounds: mixture of saturated hydrocarbons (C25 and above)
Remedies using Petrolatum · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.