Comedogenic Ratings: What They Mean and Why They're Unreliable

If you've ever googled whether an ingredient will break you out, you've probably encountered the comedogenic rating scale: a number from 0 to 5 that supposedly tells you how likely something is to clog your pores. It shows up on ingredient checker websites, skincare forums, and product reviews. It feels scientific. Quantitative. Trustworthy.

It's mostly not.

The comedogenic scale is real. The studies behind it are real. But the way it's used in consumer skincare today is disconnected from how it was generated and what it can actually tell you. Understanding the scale's origins and limitations will save you from avoiding perfectly good products and trusting the wrong ones.

Comedogenic means tending to cause comedones (clogged pores that form blackheads or whiteheads). The comedogenic rating scale of 0 to 5 was developed from studies in the 1970s and 1980s that tested pure ingredients on rabbit ears. While directionally useful, the scale does not account for ingredient concentration, product formulation, or individual skin variation.

What comedogenic means

A comedone is a clogged pore. Specifically, it's a hair follicle that gets plugged with dead skin cells, sebum, and sometimes product residue. Closed comedones appear as small, skin-colored bumps (sometimes called "texture"). Open comedones are blackheads.

An ingredient or product is comedogenic if it promotes comedone formation. Non-comedogenic means it's unlikely to clog pores. These terms describe a spectrum, not a binary. Almost nothing is absolutely guaranteed to clog pores or guaranteed not to.

The 0-to-5 scale

The comedogenic rating scale was established primarily by Fulton, Kligman, and colleagues through studies in the late 1970s and 1980s. Here's what each number means:

Rating	Meaning	Example ingredients
0	Won't clog pores	Mineral oil, petrolatum, dimethicone
1	Very low risk	Squalane, castor oil, shea butter (refined)
2	Moderately low risk	Cetyl alcohol, stearic acid, beeswax
3	Moderate risk	Myristic acid, cotton seed oil
4	High risk	Coconut oil, cocoa butter, flaxseed oil
5	Very high risk	Isopropyl myristate, acetylated lanolin

The scale is simple to use. That's part of its appeal and part of the problem.

Where the scale came from (and why that matters)

The rabbit ear model

Most of the foundational comedogenic studies used the rabbit ear assay, a method developed in the 1970s. Researchers applied pure ingredients to the inner surface of rabbit ears and measured follicular plugging after several weeks.

Rabbit ear skin was chosen because it has large, visible follicles that respond to comedogenic substances in an exaggerated way. This made it easy to observe clogging under a microscope. The problem is that rabbit ear skin is not human skin. It's significantly more reactive, more sensitive to comedogenic triggers, and structurally different.

An ingredient that causes follicular plugging in a rabbit ear may not do the same on a human face. Conversely, some ingredients that tested low on rabbit ears might still cause problems for specific human skin.

Testing pure ingredients, not formulations

The studies tested pure, undiluted ingredients. A raw dollop of coconut oil applied directly to a follicle for weeks. In real skincare, ingredients exist within formulations at specific concentrations, mixed with other compounds that can enhance, reduce, or entirely neutralize their comedogenic potential.

An ingredient with a comedogenic rating of 4 at 100% concentration might be perfectly fine at 2% concentration within a well-formulated product. The scale doesn't capture this. When you look up "coconut oil comedogenic rating 4," that tells you about pure coconut oil in a laboratory setting, not about the 1% coconut-derived fatty acid in your moisturizer.

No human replication at scale

While some later studies used human back skin or forearm testing to validate findings, there was never a comprehensive human-face-tested comedogenic database created. The ratings you see cited on skincare blogs are almost all derived from the original rabbit ear data, sometimes filtered through a single human back study.

Why the scale is unreliable in practice

Individual variation is massive

Your skin's pore size, oil production, cell turnover rate, microbiome composition, and barrier strength all influence whether an ingredient causes comedones for you. Someone with large pores and high sebum production might break out from an ingredient rated 2. Someone with tight, dry skin might tolerate an ingredient rated 4 with no issues.

There's no comedogenic rating that accounts for your specific skin. The scale gives population-level averages from non-human models. Your mileage will vary, sometimes dramatically.

Concentration matters

Coconut oil has a comedogenic rating of 4. But many products contain coconut-derived ingredients (like caprylic/capric triglyceride, which scores 1) at low concentrations. The blanket advice to "avoid all coconut derivatives" based on the rating of pure coconut oil leads people to reject products that would work fine for them.

Similarly, ingredients with high ratings are sometimes used at such low concentrations (under 1%) that their comedogenic potential is negligible in the final product.

Formulation context changes everything

The comedogenic potential of an ingredient depends on what it's formulated with. Research on product formulations shows that:

• Emulsification can reduce an ingredient's comedogenic potential
• The vehicle (water-based vs oil-based) affects delivery to the follicle
• Other ingredients in the formula can prevent or accelerate comedone formation
• Product pH influences how ingredients interact with skin

A moisturizer containing a comedogenic ingredient alongside non-comedogenic emollients, humectants, and water may have a net comedogenic potential of zero. You can't deduce a product's safety from the individual ratings of its ingredients.

The scale hasn't been updated

The foundational studies are from the 1970s and 1980s. Skincare formulation has advanced enormously since then. New delivery systems, emulsifiers, and processing methods have changed how ingredients interact with skin. The ratings haven't been revised to reflect any of this.

Common high-rated ingredients

Despite the limitations, some patterns are consistent enough to be worth knowing:

Coconut oil (rating: 4). The most commonly cited offender. Pure coconut oil applied to acne-prone facial skin clogs pores for many people. This doesn't mean every coconut-derived ingredient is problematic, but if you're acne-prone, pure coconut oil on the face is a reasonable thing to avoid.

Cocoa butter (rating: 4). Rich, occlusive, and commonly found in body moisturizers. Works well on body skin but is risky on acne-prone facial skin.

Isopropyl myristate (rating: 5). A common emollient and penetration enhancer. The highest-rated ingredient on the scale. Found in many cosmetics and some moisturizers. Worth checking for if you have unexplained breakouts.

Wheat germ oil (rating: 5). High in vitamin E but also highly comedogenic. Rarely worth the trade-off for facial use.

Flaxseed oil (rating: 4). Occasionally found in "natural" skincare products.

Commonly misleading ratings

Mineral oil (rating: 0). Despite decades of internet panic, pharmaceutical-grade mineral oil is non-comedogenic in controlled testing. It's one of the most extensively tested skincare ingredients and consistently scores 0. The fear of mineral oil clogging pores is not supported by evidence.

Petrolatum (rating: 0). Same story. Vaseline doesn't clog pores. It sits on top of skin and prevents water loss. It's the most effective occlusive available and is non-comedogenic.

Dimethicone (rating: 0 to 1). Silicone-based products are frequently accused of clogging pores. They generally don't. Dimethicone creates a breathable layer that doesn't occlude follicles.

Shea butter (rating: 0 to 2). Raw, unrefined shea butter may score higher. Refined shea butter in formulations is generally well-tolerated even by acne-prone skin.

A better approach than memorizing ratings

Patch test your actual products

The single most reliable way to know if a product will clog your pores is to test it on your skin, in its actual formulation, at its actual concentration.

Apply to a small area of your jawline or forehead nightly for 7 to 14 days. Look for new closed comedones, bumps, or blackheads. If nothing appears, the product is likely compatible with your skin. If breakouts appear in the test area, stop using it.

This takes patience, but it's infinitely more accurate than googling the comedogenic rating of every ingredient on a label.

Look for "non-comedogenic" on the label (with caveats)

The term "non-comedogenic" on product packaging is not FDA-regulated. There's no required testing standard behind it. However, reputable brands that use this label generally have done some formulation testing. It's a loose signal, not a guarantee.

Track your breakout patterns

If you consistently break out from products containing a specific ingredient, that's your personal data. It's worth more than any rating scale. Keep a note of ingredient lists from products that cause problems and look for overlapping ingredients.

Scan with HadaBuddy

When you scan a product on HadaBuddy, the app shows comedogenic ratings for individual ingredients alongside other data points like irritant potential and function in the formula. This gives you the rating as one input among many, rather than a single number to obsess over. You can compare across products on your shelf and spot patterns in what does and doesn't work for your skin.

Download HadaBuddy on the App Store. Free on iOS.

The practical takeaway

Comedogenic ratings are a starting point, not a verdict. They tell you what an ingredient did to a rabbit ear in the 1980s, not what a formulated product will do to your face in 2026.

Use the scale to flag ingredients worth watching, especially if you have acne-prone skin. But don't reject a well-formulated product solely because one ingredient has a rating above 2. And don't assume a product is safe just because everything in it scores 0. Formulation, concentration, your individual skin biology, and real-world testing matter far more than a number on a chart from four decades ago.

If your skin is breaking out, work backward from the products you're using, not from a theoretical rating database. Your face is the only test lab that matters.

FAQ

What does comedogenic mean?

Comedogenic means likely to cause comedones, which are clogged pores that manifest as blackheads (open comedones) or small skin-colored bumps (closed comedones). The term comes from "comedo," the medical name for a plugged hair follicle. A non-comedogenic product is one that's unlikely to trigger this type of clogging.

Is the comedogenic rating scale accurate?

The scale is directionally useful but not reliably accurate for individual use. It was developed from rabbit ear tests in the 1970s and 1980s using pure, undiluted ingredients. It doesn't account for formulation, concentration, or individual skin differences. Products that contain a "comedogenic" ingredient at 1% concentration may not clog pores at all.

Can a non-comedogenic product still cause breakouts?

Yes. Breakouts can be caused by factors beyond pore-clogging: irritation, allergic reactions, hormonal fluctuations, or barrier damage. A product can be non-comedogenic and still trigger breakouts through other mechanisms. Also, "non-comedogenic" on a label isn't regulated by the FDA, so the claim itself has no standardized testing behind it.

Is coconut oil really that bad for skin?

Pure coconut oil has a comedogenic rating of 4, and many acne-prone people do break out from it. However, coconut-derived ingredients (like caprylic/capric triglyceride) are chemically different and score much lower. If you're acne-prone, avoiding pure coconut oil on the face is reasonable. Coconut derivatives in formulated products are usually fine.

Does mineral oil clog pores?

No. Pharmaceutical-grade mineral oil consistently scores 0 in comedogenic testing. It's one of the most extensively tested skincare ingredients. The belief that mineral oil clogs pores is a persistent myth that originated from confusion between cosmetic-grade and industrial-grade mineral oil.

Should I avoid all ingredients with a comedogenic rating above 2?

No. That approach is overly restrictive and based on a flawed premise. The ratings test pure ingredients, not formulations. An ingredient rated 3 at 100% concentration might be perfectly safe at 0.5% within a product. Patch testing the actual product is more reliable than screening individual ingredient ratings.

How do I know if a product is breaking me out?

Introduce one new product at a time and wait 2 weeks before adding another. If breakouts appear in the first 1 to 2 weeks after starting a new product, and they're in areas you don't normally break out, the product is the likely cause. Note: this is different from purging, which only happens with actives that increase cell turnover (like retinoids or AHAs) and resolves within 4 to 6 weeks.

What's the difference between comedogenic and irritating?

Comedogenic ingredients clog pores, forming plugs (comedones) that become blackheads or bumps. Irritating ingredients cause inflammation: redness, stinging, burning, or itching. An ingredient can be one, both, or neither. Fragrance, for example, is a common irritant but isn't comedogenic. Isopropyl myristate is comedogenic but not particularly irritating.

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Further reading: How to read skincare ingredient lists · Best ingredients for fungal acne · Skincare routine for acne-prone skin · Skincare ingredients you should never mix · What 51,000 Korean skincare products reveal

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