Undaria Pinnatifida Leaf/Stem Extract

Undaria pinnatifida is a species of brown seaweed (kelp) native to the coasts of East Asia. The leaf and stem extract is derived from this macroalgae and contains naturally occurring polysaccharides, amino acids, and minerals including iodine, potassium, and magnesium.In skincare formulations, this ingredient functions primarily as an emollient and humectant. It forms a light conditioning film on the skin surface, helping to soften texture and support moisture retention without a heavy or occlusive feel.

The extract works through multiple mechanisms. The polysaccharides — particularly alginic acid and fucoidan — form a hydrating layer on the skin that helps bind water and reduce moisture loss. These compounds also have a slight film-forming property, which contributes to the conditioning effect without occluding the skin.The amino acids present may support the skin's natural moisturising factor (NMF), helping to maintain hydration within the stratum corneum. The mineral content, whilst not extensively absorbed, may provide topical benefit when left in contact with the skin.

Undaria pinnatifida extract is typically found in moisturisers, serums, and hydrating essences at low to moderate concentrations. It works well in layered routines — apply it to damp skin before an occlusive moisturiser to lock in hydration. There is no strict usage limit; it can be used daily as part of your regular skincare regimen. It pairs well with other hydrating ingredients such as glycerin and hyaluronic acid.

This ingredient is generally well-tolerated and considered safe for topical use. Those with iodine sensitivity or iodine-restricted diets should be aware that seaweed extracts contain iodine, though the amount in skincare is typically minimal.