Algae

Algae is a taxonomically broad category of photosynthetic organisms that includes everything from single-celled microalgae to large kelp. In skin care, algae extracts are used to deliver polysaccharides, amino acids, and minerals that support barrier integrity and water retention in the stratum corneum.

What it actually does

Algae-derived polysaccharides, particularly those from red and brown seaweed, form a thin film on the skin surface that slows transepidermal water loss. These polymers have a hygroscopic character, meaning they bind ambient moisture and hold it against the corneocyte layer. Certain algae also supply amino acids that replenish components of the natural moisturising factor, the blend of small molecules inside corneocytes that keeps them plump and flexible.

Beyond hydration, algae extracts can inhibit tyrosinase, the enzyme that catalyses melanogenesis, which explains their inclusion in formulas targeting uneven tone. Some species contain phlorotannins or other phenolic compounds that scavenge reactive oxygen species, offering indirect support to the lipid barrier by reducing oxidative damage to intercellular ceramides and cholesterol. The effect is cumulative rather than instant, building over repeated application.

The OVESSI point of view

We borrow from Korean layered care, where marine botanicals have always been treated as gentle humectants rather than headline heroes. Algae sits quietly in the middle of a ritual, usually in an essence or cream, where its polysaccharides work alongside other film-formers without competing for attention. Scandinavian restraint guides our dose. We use enough to measurably reduce transepidermal water loss but not so much that the formula feels tacky or heavy. French editorial luxury insists that algae be paired with ceramides or fatty acids, because hydration without lipid reinforcement is only half the job. In OVESSI formulas, algae is an architecture piece, not the facade.

What to expect, and when

Day zero to day three: the skin surface feels softer as the algae film begins to slow water evaporation. You will not see visible glow yet, only a quieter texture. Day four to day fourteen: the stratum corneum becomes more pliable. Fine lines that appear when skin is dehydrated start to look less pronounced. This is mechanical plumping, not collagen synthesis. Day fifteen to day 28: if tyrosinase inhibition is occurring, you may notice a slight evening of tone in areas of mild hyperpigmentation. The change is subtle. Algae does not erase post-inflammatory marks or melasma on its own. It supports barrier function and hydration, which in turn allows other actives to perform more predictably.

How to layer it in your ritual

Algae lives in the treat or seal step, depending on the vehicle. In an essence or serum, apply it after acids or retinoids, once the pH has normalised. The polysaccharide film will not interfere with penetration of smaller molecules that have already entered the skin. In a cream, algae acts as part of the occlusive and humectant matrix, so it comes last, sealing everything beneath. Morning or night, the logic is the same. Algae works across all skin types, though those with very oily skin may prefer it in a lightweight essence rather than a rich cream. If you layer multiple hydrators, place algae after hyaluronic acid and before oils.

Where it lives on our shelf

We include algae in formulas where barrier support and calm hydration are the primary goals. The Quiet : Sensitive Overnight Cream pairs algae extract with ceramides and niacinamide to reinforce the lipid matrix overnight, when transepidermal water loss naturally increases. The polysaccharide layer works in tandem with occlusive oils to keep the stratum corneum plump and resilient through the sleep cycle. This is where algae performs its quietest, most patient work.

Common questions

Does algae count as an active? It is a functional ingredient that measurably affects transepidermal water loss and can inhibit tyrosinase, so yes, though it is gentler than prescription actives.

Can I use algae if I have acne-prone skin? Yes, as long as the formula does not contain heavy occlusives that trap sebum, algae itself is non-comedogenic.

Is algae the same thing as seaweed? Seaweed is a subset of algae, specifically the macroalgae visible to the naked eye, but in skin care the term algae often refers to extracts from both micro and macro species.

Reviewed by

Danny Isaac, Head of Product Development, OVESSI.
Last reviewed: June 2026.

Further reading

A short, curated set of references where the science behind this page is documented in peer-reviewed literature.

1. Thambiliyagodage C, Jayanetti M, Mendis A, et al. Recent Advances in Chitosan-Based Applications-A Review. Materials (Basel). 2023;16(5). PMID: 36903188.
2. Wang HD, Li XC, Lee DJ, et al. Potential biomedical applications of marine algae. Bioresour Technol. 2017;244(Pt 2):1407-1415. PMID: 28697977.
3. Havas F, Krispin S, Cohen M, et al. A Dunaliella salina Extract Counteracts Skin Aging under Intense Solar Irradiation Thanks to Its Antiglycation and Anti-Inflammatory Properties. Mar Drugs. 2022;20(2). PMID: 35200634.