Comedogenic Scale Explained: 0-5 Ratings & What They Mean (2026)

Here is something most beauty bloggers will never admit. The comedogenic scale was originally developed by smearing skincare ingredients on rabbit ears in 1989. Yes, rabbit ears. And we have been using those exact ratings to decide whether our face creams will give us pimples for over 35 years.

That does not mean the scale is useless. It is actually one of the most powerful filters acne prone people have to avoid pore clogging products. But it also does not mean a 4 rating is a death sentence or a 0 is a guaranteed clear skin pass. The truth, like most things in skincare, sits somewhere in the messy middle.

I have spent years reading the original Fulton studies, more recent human clinical trials, and ingredient databases line by line. This guide tells you exactly what each rating from 0 to 5 means, which common ingredients fall where, when to trust the scale, and when to ignore it completely. By the end, you will read product labels with more confidence than 90 percent of skincare shoppers.

What Is the Comedogenic Scale?

The comedogenic scale is a numerical rating system from 0 to 5 that ranks how likely a skincare ingredient is to clog your pores and cause comedones, which are the technical term for whiteheads, blackheads, and the small bumps under your skin that have not yet erupted into full pimples.

The lower the number, the safer the ingredient is for acne prone skin. A rating of 0 means an ingredient has essentially no pore clogging potential. A rating of 5 means it is almost guaranteed to cause breakouts in anyone with congestion prone skin. Most ingredients fall somewhere between 1 and 3, which is exactly why the scale gets so confusing in real world use.

The scale is most useful for people with acne prone, oily, or combination skin who want to avoid breakouts caused by their skincare or makeup. It is less critical for people with dry, mature, or non reactive skin, who can often tolerate higher rated ingredients without issue.

All 6 Ratings Explained: 0 to 5

Here is what every single rating on the scale actually means in plain language, with examples of common ingredients at each level.

Where the Comedogenic Scale Came From

Knowing the history helps you understand why the scale is useful but imperfect. The original studies were not run on humans at all.

In 1972, dermatologist Albert Kligman co inventor of Retin A, developed the rabbit ear test. Researchers applied undiluted skincare ingredients to the inside of rabbit ears and counted how many comedones formed over several weeks. This became the foundation for comedogenicity research.

In 1989, dermatologist James Fulton published the most cited list ever created, ranking hundreds of common cosmetic ingredients on the 0 to 5 scale we still use today. Most online comedogenic rating charts trace back directly to his original study.

Modern testing has moved toward controlled clinical trials in humans. A 2021 randomized double blind trial tested ingredients like avocado oil, sunflower oil, and lanolin on real people and found that finished formulations with these ingredients did not significantly increase microcomedone formation. So the scale is best treated as a useful guide, not a strict law.

Common Ingredients and Their Comedogenic Ratings

Here is a practical reference table covering the ingredients you are most likely to encounter on real skincare labels. Save this section, it will save you from a lot of bad purchases.

Oils and Butters

Common Synthetic Ingredients

How to Actually Use the Comedogenic Scale

This is the part most articles get wrong. Knowing ratings is useless if you do not know how to apply them while shopping. Here is the exact process I use every time I buy a new product.

When the Comedogenic Scale Gets It Wrong

The scale has real blind spots that you need to know about. Trusting it blindly will lead you to either reject perfectly good products or trust the wrong ones.

Concentration Changes Everything

Acetylated lanolin alcohol at 100 percent is rated 4 to 5. Diluted to 2.5 percent in propylene glycol it drops to 1. The same ingredient. Drastically different real world effect. Yet the scale always shows the worst case undiluted rating.

Combinations Behave Unpredictably

Cetearyl alcohol alone has a rating of 2. Ceteareth 20 alone is also a 2. But combine them together in a formula and the comedogenic score jumps to 4. Real products are mixtures, not single ingredients.

Refinement Changes the Rating

Unrefined coconut oil is rated 4. Fractionated coconut oil is around 2 to 3. Caprylic capric triglyceride (also from coconut) is 0 to 1. All three come from the same plant but they behave completely differently on skin.

Individual Skin Variation

Some people break out from products full of 0 rated ingredients. Others happily use products loaded with 4s and 5s and stay clear. Your genetics, hormones, sebum production, and skin barrier health all play roles the scale cannot capture.

Comedogenic Scale Myths vs Facts

The skincare community has built up a lot of half truths around comedogenic ratings. Here are the four biggest ones, sorted.

Comedogenic Ratings by Skin Type

How strictly you need to follow the scale depends entirely on your skin type. Here is a practical breakdown.

Oily and Acne Prone Skin

• Stick to ingredients rated 0 to 2 in leave on products
• Avoid all 4s and 5s in moisturizers and sunscreens
• Use rinse off products (cleansers) with up to 3 ratings is usually fine
• Check the first 7 ingredients carefully before purchase
• Patch test for 10 to 14 days before full face application

Combination Skin

• Ingredients rated 0 to 2 work well in most products
• Occasional 3 rated ingredient deep in the list is fine
• Avoid 4 and 5 ratings in T zone targeted products
• Lighter formulations work better than heavy creams

Dry and Mature Skin

• Can comfortably use ingredients rated up to 3 in leave on products
• Even 4 rated ingredients like avocado oil and shea butter often work well
• Richer occlusive ingredients actually help retain moisture
• The scale matters far less for non acne prone dry skin

Sensitive Skin

• Comedogenic ratings are less relevant than irritancy ratings
• Focus on fragrance free, alcohol free formulations
• Mineral oil and petrolatum (both rated 0) are excellent for barrier repair
• Patch test even 0 rated ingredients due to sensitivity risk

Tools to Check Comedogenic Ratings Quickly

You do not need to memorize every ingredient rating. These free online tools do the work for you in seconds.

• INCIDecoder — search any product name and get full ingredient breakdown with comedogenic and irritancy scores
• SkinCarisma — flags fungal acne triggers, comedogenic ingredients, and allergens automatically
• Sezia — focused on fungal acne but includes comedogenic flags
• CosDNA — older but comprehensive database used by many K beauty enthusiasts
• SkinSort — modern interface with detailed ratings and routine planner

I personally use INCIDecoder for ingredient deep dives and SkinCarisma for quick yes or no decisions while shopping. Both are free and worth bookmarking.

Frequently Asked Questions

Final Thoughts on the Comedogenic Scale

The comedogenic scale is a tool, not a religion. It helps you make smarter choices when you do not know an ingredient, but it cannot predict exactly how your skin will react to a finished product. Use it as one factor among many, not as the only deciding factor.

If I had to summarize the entire scale into a single rule, it would be this. For acne prone skin, scan the first 6 ingredients on any leave on product. If any rate 4 or 5, put it back and find a better option. If they all rate 0 to 2, the product is worth trying with a patch test first. This single habit will protect you from 80 percent of pore clogging skincare mistakes.

The skincare industry will keep changing. New ingredients arrive every month, formulation chemistry advances, and clinical research updates old ratings. But the basic logic of the comedogenic scale, paired with reading your own skin, will keep serving you well for years to come.

This article is for educational purposes only and does not constitute medical advice. Always consult a qualified dermatologist for diagnosis and treatment of skin conditions.