Comedogenic & Irritancy Ratings

A comedogenic rating is a number from 0 to 5 that estimates how likely an ingredient is to clog pores and contribute to acne. The scale was established through decades of dermatological research, most notably the work of Dr. James Fulton, whose 1989 study in the Journal of the Society of Cosmetic Chemists tested hundreds of cosmetic ingredients using standardized rabbit ear assays. These ratings have since been refined and cross-referenced with clinical observations and remain the most widely referenced system for assessing pore-clogging potential in cosmetic ingredients.

Our comedogenic scores follow this established scale: • **0 — Non-comedogenic** — Will not clog pores. Safe for all skin types including acne-prone. • **1 — Very low risk** — Minimal chance of clogging pores. Generally well-tolerated. • **2 — Low risk** — Slight potential. May cause issues for very sensitive or acne-prone skin in high concentrations. • **3 — Moderate risk** — Noticeable potential to clog pores. Best avoided by acne-prone individuals. • **4 — Fairly high risk** — Likely to clog pores for most people. Known offenders. • **5 — High risk** — Very likely to clog pores. Classic pore-cloggers documented across multiple studies. Our product-level score is the average of all individual ingredient ratings weighted by their position in the INCI list (ingredients listed first are present in higher concentrations).

An ingredient's comedogenicity depends on several chemical and physical properties: **Fatty acid profile:** Ingredients high in oleic acid (a monounsaturated omega-9 fatty acid) tend to be more comedogenic, while those rich in linoleic acid are generally better tolerated by acne-prone skin. **Molecular weight:** Compounds with a molecular weight between 200–300 Daltons and balanced water/oil solubility (HLB around 10–12) show the highest comedogenic potential. Larger molecules (waxes, polymers) are often too big to penetrate follicles. **Ethoxylation level:** Adding ethylene oxide groups (ethoxylation) to a molecule generally reduces its comedogenicity. For example, Oleth-3 (grade 5) becomes Oleth-20 (grade 1) as ethoxylation increases. **Chain length:** Medium-chain fatty acids (C10–C16, particularly lauric and myristic acids) show higher activity than short-chain (≤C8) or long-chain (≥C18) fatty acids. **Heavy metal modification:** Adding charged molecules (zinc, lithium) or polar sugars can reduce comedogenicity by raising the HLB balance above 12.

In addition to comedogenicity, we track irritancy ratings on the same 0–5 scale. These measure the potential of an ingredient to cause inflammation, redness, stinging, or sensitisation — independent of its pore-clogging potential. • **0 — Non-irritating** — Well-tolerated even by sensitive skin • **1–2 — Mild** — May cause minor irritation in very sensitive individuals • **3 — Moderate** — Noticeable irritant potential • **4–5 — High** — Known irritants, best avoided by sensitive or compromised skin Note: An ingredient can be non-comedogenic (0) but highly irritating (4–5), and vice versa. We display both scores for a complete picture.

Based on established dermatological data, the following ingredients consistently score 4 or higher for comedogenicity: • **Isopropyl myristate** — 5 (the standard positive control in comedogenicity testing) • **Laureth-4** — 5 • **Myristyl myristate** — 5 • **Oleth-3** — 5 • **Acetylated lanolin alcohol** — 4–5 • **Isopropyl isostearate** — 4–5 • **Isopropyl linoleate** — 4–5 • **Cocoa butter** — 4 • **Coconut oil** — 4 • **Lauric acid** — 4 • **Oleyl alcohol** — 4 • **PEG-16 lanolin (Solulan 16)** — 4 • **Steareth-10** — 4 • **Stearyl heptanoate** — 4 For irritancy, watch for: **SLS/SLES** (4–5), **denatured alcohol** (4–5), **fragrance components** (variable), and **essential oils** (3–5 depending on the oil).

Comedogenic and irritancy ratings are guidelines, not absolute rules. Several factors affect how your skin will respond: **Concentration matters.** An ingredient rated 3–4 may be perfectly fine at low concentrations (below 1%) but problematic higher in the ingredient list. Our scoring accounts for ingredient position. **Formulation context.** How ingredients are combined affects absorption and activity. A high-rated oil suspended in a rinse-off cleanser is far less likely to cause issues than the same oil in a leave-on moisturiser. **Individual skin biology.** Everyone's skin is different. An ingredient rated 2 may break you out, while a 4-rated ingredient may be fine. Your skin microbiome, barrier function, and hormonal factors all play a role. **Processing matters.** Refined oils often have lower comedogenicity than their unrefined counterparts (e.g., fractionated coconut oil at 2–3 vs. unrefined coconut oil at 4). Our database uses the most common form found in commercial products. **The method matters.** Many historical ratings come from rabbit ear assays, which are more sensitive than human skin. An ingredient rated 2–3 on the rabbit ear may be perfectly non-comedogenic on human skin.

On every product page, our Comedogenic Score and Irritancy Score are calculated as follows: 1. Each ingredient in the product is matched to our ingredient database, which contains established comedogenic and irritancy ratings from peer-reviewed research and regulatory sources. 2. The average rating across all ingredients is calculated, with adjustments for ingredient position (higher-concentration ingredients carry more weight). 3. Ingredients rated 4–5 are flagged as "high risk," and ingredients rated 2–3 as "moderate risk." 4. Products with an average score ≤0.3 are classified as "Non-comedogenic," ≤1.0 as "Very low risk," ≤1.8 as "Low risk," ≤2.5 as "Moderate," ≤3.5 as "Caution," and above 3.5 as "Pore-clogging." The same methodology applies to irritancy scoring. Both scores reflect the formulation's overall tendency based on current scientific evidence, not individual responses.

You can view the comedogenic and irritancy rating of each individual ingredient on our product analysis pages. Under the "Ingredients" tab, the table includes columns for **Comedogenic Rating** and **Irritancy Rating** alongside each ingredient's name and function. This allows you to see exactly which ingredients are influencing the overall product score and make informed decisions based on your skin's specific sensitivities.

Not all oils are pore-cloggers. The key differentiator is the fatty acid profile — specifically the ratio of linoleic acid to oleic acid. Research insight: A 1986 study by Letawe et al. found that acne-prone skin consistently shows lower concentrations of linoleic acid in sebum. Topical linoleic acid application normalised this deficiency and reduced comedone count. High-linoleic oils (generally non-comedogenic, safe for acne-prone skin): • Rosehip oil (77% linoleic): Comedogenic rating 1. Also contains vitamin A precursors with mild retinol-like benefits. • Hemp seed oil (57% linoleic): Comedogenic rating 0. One of the most balanced fatty acid profiles. • Sunflower oil (68% linoleic): Comedogenic rating 0–1. Inexpensive and effective. • Grapeseed oil (73% linoleic): Comedogenic rating 1. Lightweight, absorbs quickly. High-oleic oils (higher comedogenic risk): • Coconut oil (rating 4): Despite being marketed as skin-friendly, coconut oil is one of the most comedogenic oils for acne-prone skin. • Olive oil (rating 2–3): Better tolerated than coconut but not ideal for acne-prone skin. • Shea butter (rating 0–2): Often rated low due to its stearin content, but the oleic dominance means some acne-prone individuals react. Squalane (rating 1): Despite being derived from olives, squalane is a saturated hydrocarbon — it doesn't have the same comedogenic mechanism as fatty acid oils. One of the safest oils for acne-prone skin.