Spirulina

Spirulina is technically a cyanobacterium (blue-green algae), and what makes it cosmetically interesting is phycocyanin — the blue pigment that gives spirulina its color and the antioxidant doing the heavy lifting. Phycocyanin scavenges peroxyl and hydroxyl radicals, modulates inflammatory pathways (suppresses COX-2 and prostaglandin E2), and has measurable photoprotective effects in cell-culture studies. In skincare, spirulina extract delivers a clean-beauty marketing story plus genuine antioxidant function. K-beauty brands have been using it for years (Innisfree, Mizon); Western brands have caught up via the algae-skincare trend (Algenist, Tata Harper). Distinct from chlorella (which is a true green algae, not a cyanobacterium) and not interchangeable — they pair well together because the antioxidant profiles are complementary rather than redundant.