Mineral oil is a colourless and odourless liquid, often found in cosmetics, that has received a lot of bad press by many who believe that it is a carcinogen.
Likely a big part of the confusion, mineral oil is a very imprecise name. This term has been used to refer to many different type of oils and have also been confused with or used to refer to: white oil, paraffin oil, liquid paraffin, paraffinium oil, liquid petroleum, and baby oil. All these names can refer to the same compound or another one, with a different chemical composition. To give you an example of what this means, it’s like referring to all round orange fruit as oranges but as you know grape fruit, blood orange, clementines etc are not the same fruit and don’t even taste the same. The confusion likely comes from the fact that they belong to the same family, as mineral oil compounds come from refinement processes of crude oil. To make things even more confusing, mineral oil is actually not a single compound but rather a mixture of hydrocarbons (=compounds composed of Carbon and Hydrogen atoms).
To find out if mineral oil can offer skincare benefits check out: Mineral oil in cosmetics – is it worth seeking out?
Let’s have a look at the scientific evidence on the safety of mineral oil.
The World Health Organisation, WHO, states that there is sufficient evidence that untreated or mildly treated mineral oils can cause tumours.  Additionally, branch of WHO, The International Agency for Research on Cancer, has a list of compounds and processes that could increase the risk of cancer. Their IARC monographs (=documents that identify environmental factors that can increase the risk of human cancer) list highly refined and untreated or mildly treated mineral oil as an agent that could potentially increase the risk of cancer.  They also state that exposure to mineral oil in workplaces such as workshops should be monitored, especially if it is used in mists. However, note that none of these forms or even methods of exposure to mineral oil (by inhalation) apply to cosmetics.
The purity or level of refinement of a compound or mixture also matters and it is important to note that cosmetics include a highly purified mineral oil which is generally considered safe.
Highly refined mineral oil or pharmaceutical grade, which is what is used in personal care products like cosmetics, is classed by WHO as a group 3 compound, which means that it is “Unclassifiable as to carcinogenicity to humans” and is therefore deemed safe. This is also in agreement with the European directive.  Highly refined or light mineral oil is considered so safe that is often found in baby products, often named baby oil, which is a fragrance added mixture.  Light mineral oil is also not classed for physical or health hazards according to GHS in its Material Safety Data Sheet, MSDS.  One of the main reasons for its safety is that light mineral oil is very stable and inert, meaning that it does not react with much and therefore, has very little chance of participating in any chemical reaction. Finally, the Cosmetic Ingredient Review Panel (CIR) has evaluated petroleum distillates in cosmetics and found them to be safe. 
When it comes to evaluating whether a compound or mixture is a harmful to humans, the method of exposure is also very important. For example, breathing good quality air is not only safe for humans but needed in order to stay alive, but injecting someone with a syringe full of air (or even a couple of bubbles) can cause air embolism which can kill you. As mineral oils and waxes, as used in cosmetics, do not penetrate the skin  or only penetrate a small part of it [8, 12, 13, 14] depending on their structure, the bigger potential risk would be due to ingestion from products like lipsticks or lip treatments.
The US Food and Drug Administration, FDA, states that highly refined white mineral oil is safe to use in food.  It is also approved by the FDA for medicinal applications in eyes, mouth and topical skin applications.  The European Food Safety Authority, EFSA, also approved the use of mineral oils as food additives. 
It is also important to remember that mineral oils and most ingredients, are found in cosmetics in very small amounts and quantity also plays a large role as to whether something is harmful or not. Even water can kill you if you drink more than 6-10 liters (depending on the person) within a couple of hours.
It is worth mentioning that there have been some studies looking at how much mineral oil is transferred from food packaging into the actual food (from the ink, the recycled cardboard packaging, transportation and other ways) but also studies that showed that since mineral oil is found in nature it can contaminate food in other ways too. [15, 16, 17] Contamination can begin as early as before and during harvest.  However, rest assured that food contamination with any compound, harmful or not, is a serious matter that food authorities spend time looking into.
Although there isn’t much evidence to suggest that this might cause us cancer, there are some worries from the fact that the majority of mineral oil compounds are readily absorbed by the human body and can bioaccumulate in fat cells and organs such as the lymph nodes, spleen and liver. [15, 18] Interestingly though, the concentration of mineral oil compounds found in fatty tissues are similar to those in breast milk. [15, 19] Although some studies showed that heavier mineral oil compounds can cause inflammation in various parts of the body such as the liver and the heart, there aren’t any conclusive toxicological studies on the effects of mineral oil absorption in humans. [15, 20]
There are also some concerns over mineral oil being and estrogen (=one of the female hormones) disruptor. A study published in 1960 showed that feeding female mice with mineral oil did not have an effect on estrogen processes.  Another study looking at the different mineral oil compounds found in packaging ink on food, said that 10 out of the 15 studied could potentially act as xenoestrogens (=compounds that can act similarly to estrogen).  More studies are definitely needed but one thing is clear. The confusion and contradicting results come from the fact that mineral oil can refer to a lot of different compounds, not all of which are found in cosmetics or food.
In general, safety concerns for mineral oil mainly come from the fact that it is directly linked to petroleum oil and the idea that there is petroleum in cosmetics. That is an oversimplification. It’s like saying that there are wheat plants in your cake because you added flour. Wheat plants and flour are not the same and do not even contain the same compounds as flour has gone through refinement.
What has been clear to me as a chemist looking into this was that one of the biggest problems and contributors to this confusion has been due to the fact that mineral oil is a very general term and many scientific studies that looked at the safety of mineral oil, failed to specify which compound or mixture exactly they were looking at. However, the vast majority of studies agree and show that the mineral oil found in cosmetics is safe.
Perhaps going forward both science and commercial companies should use more specific names. Specifying what type and purity of mineral oil and which compounds it contains will be very helpful, as even for me as a chemist it became very quickly confusing when all science papers and documents refer to it generally as just “mineral oil(s)”.
To conclude, there is evidence that untreated or heavy mineral oil can cause cancer, however, highly refined or light mineral oil used in cosmetics and medicine is safe, but more studies are needed to evaluate the overall effect of mineral oil in the human body.
- European Union/European Council. Directive 2003/15/EC of the European Parliament and of the Council of 27 February 2003 amending Council Directive 76/768/EEC on the approximation of the laws of the Member States relating to cosmetic products. Off J Eur Union. 2003;66:26–35.