Algae, sea kelp, seaweed: Just as we’ve gotten used to eating this stuff—wrapped around rice, or nicely spiced in a salad—now we’re being told to rub it on our skin and bathe in it. Have we gone off the deep end?With over 20 edible varieties to choose from, this green, slippery stuff has been a staple in Asian diets for thousands of years. “Seaweed is far richer in trace minerals than land plants,” explains Jenefer Palmer, founder and self-proclaimed Chief Seaweed Officer of Osea, an organic, vegan line of seaweed-based skincare. Those include vitamins, minerals, amino acids, enzymes, trace elements, calcium, magnesium, iron, manganese and zinc.MORE: 5 Exotic Greens to Add to Your DietIndeed scientists call seaweed a “functional food” due to a compound it contains called fucoxanthin, a carotenoid found in edible brown seaweeds that may posses an anti-obesity effect.But how does all this green (brown and red) goodness translate to skincare, which isn’t ingested, but applied topically?Turns out this nutritionally-dense item has anti-inflammatory properties. “For that reason alone, seaweed extracts are used for a variety of skin conditions, including acne and rosacea,” explains Joshua Zeichner, director of cosmetic and clinical research at New York City’s Mount Sinai Medical Center’s department of dermatology.“The use of seaweed as a source for healing dates back to 12,000 BC,” explains Palmer. “Ancient Greeks used it for wound recovery and Pliny the Elder describes using seaweed to treat joint disease.”MORE: How Inflammation Affects Your SkinYet not all seaweeds are created equal. Kombu, for instance, is a great source of nutritional iodine. Nori (the wrapping on your spicy tuna roll), is high in protein. And for skincare, says Palmer, “it’s hard to beat Undaria algae (commonly known as Wakame) to stimulate the production of collagen and dermal fibroblasts.”Whether these aquatic anti-agers can take on more studied, wrinkle-busters like retinol is unlikely, but there’s more than adequate proof that seaweeds are great hydrators—especially when it comes to reactive, blemish-prone skin. And it’s natural and fully sustainable. Time for a sea change.