Algae is a potent marine antioxidant used in skincare products. Two types of algae have an antioxidant effect – macroalgae and microalgae. Macroalgae are red, brown and green varieties, while microalgae are unicellular organisms that can penetrate the skin. Varieties of microalgae include spirulina, a cyanobacteria with blue-green color from phycocyanin, and chlorella, a green microalgae that grows in fresh water.