Algin / Alginate
Algin (INCI name Algin) is rated 4 on our list, 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 algin comedogenic?
Algin is rated 4 on the comedogenic scale, which is the high band.
Derived from brown seaweed, used to thicken liquids and create gel-like textures.
- Comedogenic rating
- 4 out of 5
- 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
- Seaweed Derivative / Polysaccharide / Thickener
- Also written as
- Alginate
What a 4 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 algin near the top of a label matters far more than algin 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.
Who rated it
We could not trace the 4 on our list to a paper we have read. Neither paper we could read tests any algae, seaweed or seaweed extract. 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.
What safety reviewers say
The rating above is about pore plugging. Whether algin 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 2015 review of polysaccharide gums, the panel concluded that 105 of them, algin among them, are “safe in the present practices of use and concentration in cosmetics, as described in this safety assessment”. The one gum it could not clear for lack of data was hydrolyzed carrageenan. Safety Assessment of Polysaccharide Gums as Used in Cosmetics, 2015 (opens in a new tab)
- What it does in a product (EU CosIng)
- Listed as ALGIN: binding, fragrance, viscosity controlling. CosIng entry (opens in a new tab)
- EU restrictions
- None. CosIng shows no entry for it in the annexes of the EU Cosmetics Regulation.
What we make of this. CIR's conclusion does not grade pore plugging, so on its own it neither confirms nor contradicts the 4 on our list. 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 algin comedogenic?
- Algin is rated 4 on the comedogenic scale, which is the high band. We have not found a published study that grades it, so treat this number as unconfirmed.
- Is algin non comedogenic?
- No. Algin is rated 4 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 algin's comedogenic rating?
- 4 out of 5 on our list. It is classed as Seaweed Derivative / Polysaccharide / Thickener. 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.”