Is isostearic acid non comedogenic?

No. Isostearic Acid is rated 4–5 on the comedogenic scale, which is the high band. That is the number on our list rather than a verdict on any product. We have not traced it to a published study, so treat it as unconfirmed.

What is isostearic acid's comedogenic rating?

4–5 out of 5 on our list. It is classed as Fatty Acid(s). We have not found a published study that grades it, so treat this number as unconfirmed.

Isostearic Acid

Isostearic acid (INCI name Isostearic Acid) is rated 4 to 5 on our list, a range whose top puts it in the high band, and that number is unconfirmed: we have not traced it to a published study (what unconfirmed means).

Like every rating here, it is for the raw ingredient tested alone, and a label does not print how much of it a product holds.

Is isostearic acid comedogenic?

4–5 High unconfirmed

Isostearic Acid is rated 4–5 on the comedogenic scale: our list gives it a range from 4 to 5, and the band follows the 5 at the top.

A liquid fatty acid used as an emulsifier and binder in cosmetics and makeup.

Comedogenic rating: 4–5 out of 5 (a range on our list)
Band: High: Clear plugging in the rabbit-ear test. The first band to check in a leave-on product.
Where the number comes from: Unconfirmed. We could not trace this rating to a study we have read; the section on who rated it says what we checked.
Composition: Fatty Acid(s)
Also written as: No common variants recorded

Where Isostearic Acid sits on the 0 to 5 comedogenic scale. Our list gives a range, so the whole range is drawn and the band follows the higher end. The papers we checked it against are under Sources we checked this rating against further down this page.

What a 4–5 means in practice

A 4 or 5 is the top of the scale. In the rabbit-ear test, Fulton 1989 counted 4 to 5 as a clear positive: the ingredient plugged the follicles, and did so repeatably. A person's skin reacts less readily than a rabbit's ear, and a product holds far less of the ingredient than the test did, so treat this band as the first thing to check in anything that stays on your skin. It does not prove the ingredient will cause a breakout. A rinse-off product is on the skin for seconds.

Two things change what this number is worth. Ingredients are listed in descending order of concentration, so isostearic acid near the top of a label matters far more than isostearic acid at the bottom. And the rating describes the raw ingredient on its own. A 2006 review in the Journal of the American Academy of Dermatology found that a rating for a single ingredient does not reliably predict how a finished formula behaves on human skin. The full story of the scale is here.

Check a whole ingredient list

Who rated it

We could not trace the 4–5 on our list to a paper we have read. Neither paper we could read tests isostearic acid. The list does not say where its numbers came from, so treat this number as unconfirmed rather than as one we can tie to a table.

A grade is for the raw ingredient tested alone on a rabbit's ear, which reacts more readily than human skin. It says nothing about how much of it a product holds or what the rest of the formula does.

Others in the same family

Fatty Acid · 4 ingredients on this list

Fungal acne

Isostearic Acid matches rule 1, fatty acid, C12 to C24 , on the fungal acne checker. Isostearic acid, C18. The rule comes from lab studies of what Malassezia yeast can feed on, and it is not a verdict on any product.

What safety reviewers say

The rating above is about pore plugging. Whether isostearic acid is safe to use in cosmetics is a separate question. Below is the conclusion of the Cosmetic Ingredient Review (CIR), a US expert panel, and what the EU ingredient database, CosIng, lists for it. We quote CIR's conclusion as written, read on 31 October 2026.

Cosmetic Ingredient Review (US): In a 2019 review of 102 fatty acids and fatty acid salts, isostearic acid among them, the panel concluded they are “safe in the present practices of use and concentration described in the safety assessment when formulated to be non-irritating and non-sensitizing, which may be based on a QRA”. A QRA is a quantitative risk assessment. Safety Assessment of Fatty Acids & Fatty Acid Salts as Used in Cosmetics, 2019 (opens in a new tab)
Pore plugging in the same report: The same report describes a rabbit-ear test of a product formula with and without 2.5% isostearic acid: “the formulation with Isostearic Acid was both irritating and comedogenic”.
What it does in a product (EU CosIng): Listed as ISOSTEARIC ACID: binding, cleansing, surfactant (emulsifying), surfactant (cleansing). CosIng entry (opens in a new tab)
EU restrictions: None. CosIng shows no entry for it in the annexes of the EU Cosmetics Regulation.

CIR was set up in 1976 by the US cosmetics trade association, now the Personal Care Products Council, and the Council funds it. CIR states that its panel and review process are independent of the Council and the cosmetics industry. CIR's statement (opens in a new tab). The FDA does not approve cosmetic ingredients before they go on sale, except colour additives, and the companies that make and sell cosmetics are legally responsible for their safety. FDA's page (opens in a new tab).

What we make of this. CIR's conclusion does not grade pore plugging, so on its own it neither confirms nor contradicts the 4–5 on our list. The report does print one pore-plugging result, quoted above, and we give it as one more data point beside our rating. A safety review looks at things like irritation, allergy and toxicity at the amounts products use, and the rating is only about pores, so read them side by side.

Common questions

Is isostearic acid comedogenic?: Isostearic Acid is rated 4–5 on the comedogenic scale: our list gives it a range from 4 to 5, and the band follows the 5 at the top. We have not found a published study that grades it, so treat this number as unconfirmed.
Is isostearic acid non comedogenic?: No. Isostearic Acid is rated 4–5 on the comedogenic scale, which is the high band. That is the number on our list rather than a verdict on any product. We have not traced it to a published study, so treat it as unconfirmed.
What is isostearic acid's comedogenic rating?: 4–5 out of 5 on our list. It is classed as Fatty Acid(s). We have not found a published study that grades it, so treat this number as unconfirmed.

Sources we checked this rating against

Kligman AM, Kwong T. “An improved rabbit ear model for assessing comedogenic substances.” British Journal of Dermatology, June 1979;100(6):699–702. (opens in a new tab) The rabbit-ear assay behind published 0 to 5 comedogenicity grades.
Fulton JE Jr. “Comedogenicity and irritancy of commonly used ingredients in skin care products.” Journal of the Society of Cosmetic Chemists, November/December 1989;40(6):321–333. (opens in a new tab) Rabbit ear. Each ingredient at 10 percent in propylene glycol unless stated, applied five days a week for two weeks, and graded 0 to 5 from the width of the follicles, measured by micrometer and under the microscope. The paper counts 0 to 1 as not significant, 2 to 3 as borderline and 4 to 5 as positive. Some grades depended on the supplier of the raw material, and some oils were also tested refined.
Draelos ZD, DiNardo JC. “A re-evaluation of the comedogenicity concept.” Journal of the American Academy of Dermatology, March 2006;54(3):507–512. doi:10.1016/j.jaad.2005.11.1058 (opens in a new tab) Tested finished products on the backs of six people and concluded that “Finished products using comedogenic ingredients are not necessarily comedogenic.”

The rating and description above are the ones this site publishes on its A–Z list. The papers above are the ones we checked it against, and the section on who rated it says whether any of them graded this ingredient.