Yes, Vicks VapoRub is flammable. The product’s base is petrolatum (petroleum jelly), and it contains several volatile essential oils, all of which can ignite when exposed to heat or an open flame. Poison Control states plainly that “Vicks VapoRub is flammable and should not be heated.”
What Makes VapoRub Flammable
The biggest factor is the petrolatum base, which makes up the bulk of the ointment. Petrolatum is a refined petroleum product, and like other petroleum-based substances, it can catch fire when it reaches a high enough temperature. On top of that base, VapoRub contains a mix of essential oils that are individually flammable: camphor (4.8%), eucalyptus oil (1.2%), menthol (2.6%), cedarleaf oil, nutmeg oil, turpentine oil, and thymol. Turpentine oil in particular has a long history as a solvent and is well known for its low ignition threshold.
Under normal use, rubbing a small amount on your chest at room temperature, the product is not going to spontaneously combust. The risk comes when VapoRub is exposed to a direct heat source or open flame.
Heating VapoRub Is Especially Dangerous
A common home remedy involves melting VapoRub in hot water or a microwave to inhale the vapors. This is one of the most dangerous things you can do with the product. The manufacturer’s label warns explicitly: do not heat, microwave, or add to hot water.
There are published medical cases of people heating VapoRub in a microwave and having the product explode. In one case, a person placed the ointment in a glass container with water and microwaved it. In another, the ointment was heated without water. Both times the product erupted violently, causing severe eye injuries that required surgery. Poison Control notes that thermal and chemical burns can occur when heated VapoRub contacts skin.
The essential oils in VapoRub become more volatile as they heat up, releasing flammable vapors. In a sealed or semi-sealed container like a microwave, pressure builds rapidly. The result is not a slow melt but a sudden, forceful splatter of scalding, oil-laden material.
Open Flames and Cigarettes
Applying VapoRub and then lighting a cigarette, using a gas stove, or standing near a candle creates a real burn risk. Research on petroleum-based ointments and wound dressings found a 5% incidence of self-inflicted burn injuries caused by patients igniting facial dressings with tobacco products. VapoRub sits in the same category of petroleum-based products associated with fire risk for people who smoke or work near open flames.
The danger increases with a thin layer of product. A thin coat of any petroleum-based ointment ignites more easily than a thick glob because the thin layer cannot dissipate heat as effectively, allowing it to reach ignition temperature faster.
Extra Risk With Supplemental Oxygen
If you or someone in your household uses supplemental oxygen, VapoRub becomes significantly more hazardous. Petroleum-based ointments are flammable in any oxygen-enriched environment, meaning air with oxygen concentrations above about 30% (normal room air is 21%). Supplemental oxygen delivered through a nasal cannula or face mask creates exactly this kind of enriched zone around the nose and mouth, which is precisely where people tend to apply VapoRub.
The Anesthesia Patient Safety Foundation identifies the combination of a petroleum-based fuel source, concentrated oxygen, and any nearby ignition source (even a small spark) as the conditions for a serious fire. Applying VapoRub on or near the face while using oxygen therapy is a combination worth avoiding entirely.
How to Use VapoRub Safely
At room temperature and away from flames, VapoRub is safe for its intended purpose: rubbing a thin layer on the chest, throat, or back to relieve cough and congestion. The key precautions are straightforward:
- Never microwave it. There is no safe way to heat VapoRub in a microwave, even with added water.
- Keep it away from open flames. Don’t apply it and then smoke, light candles, or cook over a gas burner.
- Don’t add it to boiling or very hot water. The product can splatter and cause burns on contact.
- Avoid use with supplemental oxygen. The petroleum base and enriched oxygen create conditions for ignition.
- Store it at room temperature with the lid tightly closed, away from heat sources.
If you want to inhale menthol or eucalyptus vapors for congestion relief, purpose-built steam inhalers or VapoRub’s own non-heated products (like shower tablets or plug-in units) are far safer options than improvising with a microwave or stovetop.