The ingredients most likely to break you out

The comedogenicity scale most skincare guides reference traces back to a 1972 paper by Albert Kligman and James Fulton, the dermatologists who developed the rabbit ear assay. They applied concentrated ingredients to the inner ear of New Zealand white rabbits, waited two weeks, then biopsied the follicles to score how many microcomedones had formed. Each ingredient got a rating from 0 (no comedones) to 5 (severe follicular plugging). The list became the foundation for nearly every "comedogenic ingredient" chart you see today.

The rabbit ear model was useful for its time, but it has serious limitations. Rabbit follicles are far more sensitive than human follicles. The test was usually run at 100% concentration, which almost no real product contains. It ignored vehicle effects: the same ingredient behaves differently in a water-based serum versus an occlusive balm. And it ignored individual variation entirely. Two humans can use the same product and get opposite results, because pore size, sebum chemistry, and microbiome composition all differ.

Modern dermatology treats comedogenicity ratings as a starting hypothesis, not a verdict. A 5 out of 5 ingredient at 0.1% buried in a thoughtful formula can be fine. A 2 out of 5 ingredient at 25% in an occlusive cream can absolutely break you out. The label "non-comedogenic" on a finished product is not regulated in the United States, so it carries no guarantee. The most reliable way to know whether an ingredient is a problem for you is still to track your routine and your skin together over time, which is exactly what this guide is built around.

Most "pore-clogging" lists conflate three very different mechanisms. Untangling them helps you read ingredient labels more usefully and avoid eliminating ingredients that are not actually your problem.

The first mechanism is direct comedogenicity. The ingredient sits in the follicle and physically blocks normal sebum flow, which lets dead skin and oil pile up behind it. Classic offenders here are isopropyl myristate, lanolin, coconut oil, and certain heavy butters. These tend to score high on the rabbit ear assay because the assay specifically measures follicular plugging.

The second mechanism is fungal-acne feeding. Malassezia is a yeast that lives on everyone's skin, and under the right conditions it overgrows inside follicles and produces the small uniform bumps people call fungal acne or pityrosporum folliculitis. Malassezia metabolises specific fatty acids with carbon chains between roughly C11 and C24. Ingredients that supply these substrates (coconut oil and its derivatives, algae extract, many essential oils, fatty acid esters) can feed a malassezia bloom even though the ingredient itself does not directly clog follicles.

The third mechanism is barrier damage and irritation. When a cleanser, solvent, or fragrance compromises your stratum corneum, your skin enters a state of low-grade inflammation. Inflamed skin overproduces sebum, sheds keratinocytes irregularly, and is far more vulnerable to comedone formation. Sodium lauryl sulfate, denatured alcohol, fragrance, and some essential oils sit in this category. They do not clog pores directly, but they create the conditions where pores clog more easily. Knowing which mechanism you are dealing with changes how you fix it.

What follows is a short profile of each of the eight ingredients most often flagged in research, dermatology textbooks, and patch-test data. Each one has its own deep-dive article on this site if you want the full mechanism, the studies, and the substitution options.

1. Fragrance (parfum)

Fragrance is not a single ingredient, it is a regulatory category that can hide dozens of individual aroma chemicals behind a single label. The North American Contact Dermatitis Group has consistently ranked fragrance mix as one of the top cosmetic allergens, and a meaningful share of "sensitive skin" reactions trace back to it. Fragrance does not directly clog pores, it works through the third mechanism, barrier damage and inflammation. Repeated exposure can cause low-grade contact dermatitis that looks like adult acne, redness, and uneven texture. It hides in moisturisers, cleansers, sunscreens, and even products labelled "unscented" (which often use masking fragrance to cover raw-ingredient odour). If you are trying to stabilise a reactive skin barrier, fragrance-free is the cleanest baseline. Read more: /fragrance-and-acne

2. Coconut oil

Coconut oil is the textbook example of why ingredient lists alone do not tell the whole story. It is rated 4 out of 5 on the comedogenicity scale, and its dominant fatty acid (lauric acid, C12) is a known substrate for malassezia, which means it can hit you through both mechanism one (direct comedogenicity) and mechanism two (fungal-acne feeding). It became popular as a "natural" face oil and oil cleanser, and it lives on in lip balms, body butters, hair masks that drip onto the back, and "clean beauty" makeup removers. People with oily, acne-prone, or fungal-acne-prone skin almost universally do worse with coconut oil on the face. People with very dry skin sometimes tolerate it body-only without issue. Read more: /coconut-oil-and-acne

3. Isopropyl myristate

Isopropyl myristate (IPM) is one of the few ingredients that scored a clean 5 out of 5 on the original Kligman assay. It is an ester of isopropyl alcohol and myristic acid, used as an emollient and penetration enhancer because it has a very light, dry, silky finish. That same property is what makes it a problem: it slips into follicles easily and is highly comedogenic at typical use concentrations. You will find it hiding in lightweight moisturisers, primers, sunscreens (especially the cosmetically elegant ones), and pre-shave oils. The "-myristate" suffix is the giveaway, and so are its cousins isopropyl palmitate, isopropyl isostearate, and myristyl myristate, which behave similarly. Read more: /isopropyl-myristate-and-acne

4. Algae extract

Algae extract is the surprise entry on most fungal-acne sufferers' avoidance lists. It rarely shows up on traditional comedogenicity charts because it does not directly plug follicles. The problem is mechanism two: many algae extracts and seaweed-derived ingredients carry fatty acids in the C11 to C24 range that malassezia metabolises, plus traces of free fatty acids from cell-wall lipids. It is increasingly common in "clean," "marine," and "hydrating" skincare, especially serums and sheet masks marketed for plumping or barrier repair. If you have small uniform bumps on the forehead, chest, or hairline that do not respond to benzoyl peroxide, an algae extract in your routine is worth investigating. Read more: /algae-extract-and-fungal-acne

5. Sodium lauryl sulfate

Sodium lauryl sulfate (SLS) is a sulfate surfactant prized for producing thick, satisfying foam. It is also one of the most thoroughly documented barrier-disrupting ingredients in dermatology. It is the standard positive control in irritancy patch tests, which is to say, researchers literally use it as the benchmark for "this irritates skin." On the face, SLS is a mechanism-three ingredient: it strips intercellular lipids, raises transepidermal water loss, and primes skin for inflammation. It is most common in foaming face washes, shampoos that drip down the face and back, and toothpaste (a frequent trigger of perioral dermatitis). The closely related sodium laureth sulfate (SLES) is gentler but still worth noting. Read more: /sodium-lauryl-sulfate-and-acne

6. Lanolin

Lanolin is the waxy substance secreted by sheep to waterproof their wool, and humans have been smearing it on skin for centuries because it is an exceptional emollient and humectant. It is also rated 4 to 5 out of 5 for comedogenicity, and the North American Contact Dermatitis Group has tracked it as a top-tier contact allergen for decades, particularly in atopic patients. Modern "purified" lanolin is somewhat better tolerated than older grades, but it still triggers breakouts and rashes in a non-trivial percentage of users. It is most often encountered in lip balms (where lip-area cystic acne is the giveaway), nipple creams, hand and foot balms, and "natural" multipurpose ointments. Read more: /lanolin-and-acne

7. Essential oils

Essential oils are concentrated plant aromatics, and their reputation in skincare oscillates between miracle and menace. The reality is mixed. Tea tree oil at low concentrations has decent evidence for inflammatory acne. Most others (lavender, peppermint, citrus, rose, ylang ylang, eucalyptus) are at best neutral and at worst significantly irritating. Citrus oils contain furocoumarins that cause photosensitisation, which means sun exposure after application can trigger a burn-like reaction or persistent hyperpigmentation. Many essential oils also carry fatty acids that feed malassezia, so they hit through both mechanism two and mechanism three. They are common in "natural" and "aromatherapy" skincare, deodorants, and DIY recipes. Read more: /essential-oils-and-acne

8. Alcohol denat

This is where ingredient literacy matters most, because not all "alcohol" is the same thing. Denatured alcohol (also called alcohol denat, SD alcohol, or ethanol) is the drying kind: small-molecule solvents that flash off the skin and take water and lipid with them. They are often used to make a product feel light and fast-absorbing, especially in toners, gel sunscreens, mists, and astringents. Used heavily, they damage the barrier and trigger mechanism three. The fatty alcohols (cetyl alcohol, stearyl alcohol, cetearyl alcohol, behenyl alcohol) are completely different. They are waxy emollients used to thicken and stabilise moisturisers, and they are not drying or comedogenic for most people. If your sunscreen lists "alcohol denat" in the top five and your skin has been getting tight and reactive, that is your prime suspect. Read more: /alcohol-denat-and-acne

Ingredient lists in the United States and EU are sorted by concentration down to about 1%, after which the order is flexible. That means the top five ingredients matter far more than the bottom twenty, both for what is helping you and for what might be hurting you. A comedogenic ingredient at position 23 in a serum is rarely the source of your breakouts. The same ingredient at position 3 in a moisturiser is a different conversation.

Skim the top five entries first. Watch for "fragrance" or "parfum" near the top, which signals a heavily scented formula even if the marketing says "lightly scented." Watch for "alcohol denat," "SD alcohol 40," or "ethanol" near the top, which signals a drying base. Watch for ingredient names ending in "-myristate," "-palmitate," "-stearate," "-isostearate," and "-oleate," which are fatty acid esters that often score moderately to highly comedogenic. Watch for any oil whose name you recognise from the comedogenic lists (coconut, cocoa butter, shea, wheat germ, flaxseed) appearing in the top portion of the list.

Conversely, do not panic over fatty alcohols. Cetyl, stearyl, cetearyl, and behenyl alcohol are waxy thickeners, not solvents, and they are well tolerated by most acne-prone skin. Do not panic over "alcohol" appearing inside a longer ingredient name (benzyl alcohol, phenoxyethanol) at the bottom of a list, those are preservatives at small concentrations. And do not assume "non-comedogenic" on the front of the bottle has been verified by anyone, the term is not regulated in the United States. Fungal-acne-safe ingredient checkers exist online and are useful as a starting filter if you suspect malassezia involvement, but no list replaces tracking your own skin's response.

Generic comedogenicity charts answer a generic question: across a population of rabbit ears in 1972, did this ingredient produce follicular plugging? The question you actually want answered is different: across the past three months of your specific routine, your specific stress and sleep, and your specific skin, which ingredients line up with your breakouts? That is a correlation problem, and the only way to solve it is with day-by-day data on what you used and how your skin responded.

ClearSkin is built around exactly this loop. You log every product in your routine and the ingredients in each product (you can scan a barcode where supported, or paste an INCI list, or pick from existing entries). Each day you log skin status: new lesions, location, redness, oiliness, any inflammation. You also log the things that interact with skin from the inside: sleep, stress, diet, cycle phase, supplements. Everything stays on your device. There is no account, no cloud, no telemetry, no ad targeting, and no paywall.

What you get back is a personal correlation map. If isopropyl myristate appears in three products in your current routine and your jawline lesions cluster in the days after you use those products, ClearSkin shows you that pattern. If you stop using a product and the bumps fade over the next three weeks, the timeline makes that obvious. The point is not to demonise any single ingredient, formulators put isopropyl myristate or coconut oil in products for real reasons, and plenty of people tolerate them well. The point is to stop arguing with rabbits from 1972 and start listening to your own skin. Most users find their first ingredient-level insight within two to three weeks of consistent logging.