Search for any plant oil and you will find a "comedogenic rating" from 0 to 5, supposedly telling you how likely it is to clog pores. The numbers are repeated so often that they look like settled science. They are not.
Where the ratings come from
Most of the lists trace back to studies from the 1970s and 1980s that applied pure ingredients to the inner ear of rabbits, a site that is far more sensitive than human facial skin. Later work found that results did not always match what happens on people, and that the same ingredient behaves differently depending on concentration and on the rest of the formula.
So a rating can be a rough hint, but it cannot predict how a finished product will behave on your face.
What does seem to matter
- Fatty-acid balance. Some research suggests that people with acne have relatively low levels of linoleic acid in their skin surface lipids. That is one reason linoleic-rich oils such as sunflower, safflower and grapeseed are often suggested for breakout-prone skin, though the evidence is limited.
- Heavy, occlusive textures. Thick oils and butters left on oily skin all day are more likely to be a problem than a few drops of a light oil at night. Coconut oil and cocoa butter are often reported as troublemakers on the face.
- Fragrance and essential oils. These can cause irritation that looks like breakouts, especially around the mouth and chin.
How to test an oil yourself
- Introduce only one new product at a time.
- Try it on a small area, such as along the jawline, for a week or two before using it all over.
- Use a small amount, two or three drops, preferably in the evening.
- Stop if you notice new bumps, redness or itching in that area.
Breakouts that are deep, painful or leave scars need medical treatment, not experiments with oils. A GP or dermatologist can prescribe effective options.
Context matters too
Sweat, friction and touching your face can all trigger breakouts on their own. Long evenings resting your chin on your hand, whether at a desk or at a blackjack table, deserve as much suspicion as a new face oil. Clean hands and a clean pillowcase are unglamorous but useful habits.
