Choosing the wrong product can quietly clog your pores and set off a run of breakouts. That is why so much skincare advice now revolves around the word comedogenicity. The trouble is that the term is used loosely and often misunderstood. Some people swear by it, while others dismiss it as marketing. This article explains what comedogenicity actually means, how the rating scale works and what it can tell you about pore-clogging ingredients. It also looks at how useful the scale really is, with some practical tips for making smarter choices.
What is Comedogenicity?
In skincare, comedogenicity is the likelihood that an ingredient will clog your pores and cause blackheads and whiteheads. It is worth being clear that this is not the same as purging. Purging happens when certain actives speed up skin turnover and cause temporary breakouts, whereas comedogenic ingredients physically block the pore. The concept gained traction in the 1970s, when researchers noticed that some cosmetic ingredients were worsening acne in certain people.
Those early studies tested ingredients on animals such as rabbits and found that some substances blocked pores quickly. The findings shaped much of what we understand about comedogenicity today. However, alongside the ethical concerns, scientists soon realised that animal testing did not always translate to human skin. In the 1980s, researchers moved to more relevant tests on human volunteers, usually by applying substances to the back to see whether they blocked pores. This built up a working picture of comedogenicity in humans and a database of ingredients ranked by their likelihood of clogging pores.
How Does the Comedogenic Scale Work?
To help shoppers and doctors gauge the pore-clogging potential of ingredients, researchers developed a comedogenicity rating system. The scale gives each ingredient a number based on how likely it is to block pores and trigger blemishes. It is a popular tool for guiding product choice, especially for acne-prone or oily skin. Most charts rate ingredients from 0 to 5, though some only run from 0 to 3. Either way the message is the same, with higher scores meaning a greater risk. A typical scale looks like this:
- 0: non-comedogenic and very unlikely to clog pores.
- 1 to 2: low pore-clogging potential.
- 3 to 5: an increasing potential to cause blemishes.
Common ingredients vary widely in their ratings. For instance, coconut oil and cocoa butter often score 3 to 5, which makes them more likely to clog pores, particularly on acne-prone skin. Oleic acid and lanolin tend to fall in the same higher-risk range. At the other end, jojoba oil, hemp seed oil, glycerin and hyaluronic acid usually score 0 to 2. That makes them less likely to block pores, and they may suit reactive or breakout-prone skin better. As a general rule, if you have oily or acne-prone skin, lean towards products rated 0 to 2. If a particular product has caused congestion before, identify the likely culprit, then use the scale to steer clear of similar ingredients.
What Are the Limitations of the Comedogenic Scale?
The comedogenic scale is a useful starting point, but it is far from perfect. The ratings come from a mix of lab tests, animal studies and human trials. They do not always reflect how an ingredient behaves once it is blended into a finished product and used on real skin. A few limitations are worth keeping in mind.
- Test methods do not reflect real use: Data from animal and cell-culture studies cannot fully represent human skin. Even human back tests differ from facial skin, so there is a limit to how far this data extrapolates to everyday use.
- Concentration matters: An ingredient can be comedogenic at full strength yet harmless at the 2 to 10% used in a real formula. Acetylated lanolin alcohol, for example, scores 4 to 5 when pure but may drop to 1 at low percentages.
- Formulation matters: A product is more than its individual actives. Emulsifiers, pH, texture and the way ingredients interact all affect the pore-clogging risk.
- Individual skin variation: Your response is your own. Genetics, oil composition and sensitivity all influence whether a given ingredient causes you problems.
- No legal definition: Neither UK nor US regulators formally define “non-comedogenic”. Brands can use the label without standardised testing, which often makes it more marketing than medicine.
How Do You Keep Your Pores Clear?
Knowing which ingredients carry a higher risk is useful, but it is only part of the picture. To genuinely lower your chance of breakouts, it helps to build good habits and personalise your skincare routine to your skin. These are our top tips for smarter choices.
- Scrutinise ingredient lists: Focus on the first six to eight ingredients, since these make up most of the formula. Check that none are highly comedogenic or have caused you problems before.
- Patch-test every new product: Apply it behind your ear or along your jawline for 48 hours and watch for irritation or breakouts.
- Introduce one product at a time: That way, if your skin reacts, you will know exactly what caused it and can avoid ingredients with a similar profile.
- Use ingredient lookup tools: Reputable websites and apps that list comedogenic ratings can be a helpful cross-check.
- Choose the right actives: If you are acne-prone, prioritise ingredients that control oil and keep pores clear. Exfoliating acids like salicylic acid and other BHAs clear dead skin and prevent congestion, while benzoyl peroxide and retinoids like tretinoin and adapalene treat and prevent acne. For hydration, hyaluronic acid and glycerin add moisture without clogging pores, and zinc PCA can help control oil.
- Seek help: If you are really struggling, speak to a dermatologist or healthcare provider. They can help you put together a plan that targets your concerns without triggering breakouts or irritation.
Comedogenicity is not a worry for everyone. It depends on your skin type and whether you have an underlying skin condition. Often the most useful guide is simply how your skin has reacted to ingredients in the past, since that points you towards the ones that cause you trouble. The scale is, however, a helpful direction-finder even though it is not an exact science. Treat the ratings as a guide, alongside ingredient concentration, the overall formulation and your own skin’s responses. With a little patience and a methodical approach, you can build a routine that genuinely works with your skin.
At City Skin Clinic, we believe that skincare is personal. Through our online clinic, our doctors create bespoke compounded treatments using ingredients like tretinoin, spironolactone, azelaic acid and hydroquinone where appropriate. They treat a range of concerns including acne, hyperpigmentation, melasma and skin ageing. To start a plan built around your skin, book a video consultation or complete our online consultation form. The journey towards great skin starts here.
This article is intended for general informational purposes only and is not a substitute for medical advice, diagnosis or treatment. Always consult a qualified medical provider for any medical concerns or questions you might have.
