Biossance Squalane + BHA Pore-Minimizing Toner Versus Beauty of Joseon Green Plum Refreshing Toner : AHA + BHA

The extract itself has demonstrated antioxidant, soothing, and potential anti-allergy properties.

Most of this research is done in vitro and dedicated clinical studies on topical application are still limited.

Lab testing does back up decent antioxidant activity for this species. A study comparing twelve red seaweeds found Corallina Officinalis stood out for its free-radical scavenging capacity. And a separate study found meaningful radical scavenging plus antibacterial activity from the raw biomass.

It's worth being clear that most of this is test-tube work on raw-algae and not a clinical trial on a finished cream.

On concentration, a 2020 industry survey found it's used at up to 2% in makeup and skincare. Safety-wise, it's as boring as it gets: the Cosmetic Ingredient Review Expert Panel concluded this ingredient (along with the powder, Thallus Extract, and Hydrolyzed versions) to be safe as used in cosmetics and cited negative sensitization data.

There's no meaningful record of it causing allergic contact dermatitis, but be sure to patch test if you are unsure.

You'll see algae/seaweed listed as a 5/5 on a lot of pore-clogging charts and that number doesn't come from anywhere; it's not in the original rabbit-ear studies that most comedogenic ratings trace back to.

The reasoning behind the reputation is that seaweed is high in iodine and iodine can trigger acne-like breakouts when eaten. This traces back to a 1976 letter in Archives of Dermatology describing two women whose breakouts cleared after they stopped taking high-dose kelp supplements orally.

And the reaction of these two women wasn't clogged pores at all: it was an iodine-triggered pustular rash. Later research found normal dietary iodine doesn't meaningfully affect acne either and nobody has shown topical seaweed delivers enough iodine to matter.

What we do have is dozens of brown and red algae ingredients found to be non-irritating and non-sensitizing, and a handful of studies that found algae compounds may actually help acne.

However, plenty of people do report breaking out from algae-containing products. Skin is individual and it's worth avoiding if yours has reacted to algae before.

This ingredient contains a group of yellow pigments called curcuminoids (mostly curcumin) that give it genuine antioxidant and anti-inflammatory activity in skin.

Reviews of topical clinical studies have found turmeric/curcumin to be generally well-tolerated and useful across conditions like eczema and mild inflammation.

One thing working in its favor is that curcumin barely penetrates; in lab skin-permeation testing, the curcuminoids mostly stayed in the outermost layer of skin. This is a good thing because its soothing and antioxidant activity is a surface-level job anyway.

At this time, industry data shows there's no single "correct" cosmetic percentage. It's used across a wide range depending on the product and varies from tiny fractions of a percent up to a few percent.

Allergy-wise, curcumin is a documented (but uncommon) contact allergen. It can also cross react with related plants, so anyone with a turmeric/ginger/cinnamon allergy or reactive skin should patch test first.