Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 12/21/2020
In search of the best beauty products, we likely spend thousands of dollars over our lifetimes.
Chasing the skin health benefits that will give us glowing, ageless complexions can feel a little like looking for treasure — a lot of time and energy spent with very little to show for it.
So when a product contains an ingredient like seaweed or seaweed extract and promises hydrating, detoxifying, anti-aging, anti-acne and anti-inflammatory benefits, it’s understandable to want to give it a shot — or at least do a little research.
After all, truly healthy skin is worth the effort. But are the purported benefits of seaweed backed by science?
Abundant undersea plant life, seaweeds are photosynthetic algae, which means like above-ground plants, they require sunlight to live.
Though there are thousands of species of seaweed, they can all be classified into three groups:
Brown algae (Phaeophyceae)
Green algae (Chlorophyta)
Red algae (Rhodophyta)
Some types of seaweed are an everyday item in Chinese, Korean, and Japanese diets, and they’ve been eaten since prehistoric times. In Japan alone, about 21 species of seaweed are used in everyday cooking.
Seaweed is abundant in amino acids and proteins, polysaccharides, fatty acids, phenolic compounds, vitamins, sterols and more.
Some species contain 10 to 100 times more vitamins and minerals than above-ground plant or animal food sources.
For instance, one variety of red algae (Palmaria palmata) contains dramatically more iron by weight than lean beef.
In addition to serving dietary purposes, seaweed is used in skin care applications.
In addition to being diet staples, seaweed has been used for ages in the treatment of skin conditions. The reported benefits of seaweed are said to be derived from their phenolic compounds, polysaccharides, pigments, sterols and other active components.
For example, water-soluble phenolic compounds made up of building blocks such as flavonoids have antioxidant, antimicrobial and anti-inflammatory properties.
Phlorotannins, a phenolic compound found in brown seaweed, may have antioxidant, anti-aging and anti-melanogenesis (whitening or anti-hyperpigmentation) applications.
Many amino acids can be found in seaweed, including: proline, alanine, arginine, tyrosine and more. These can have natural moisturizing benefits and serve as a UV protectant.
Much if not most of the research on the potential skin care benefits of seaweed are either done in a lab (not reproduced on humans) or done using components typically found in seaweed, but without a clear cause-effect relationship between the result and the seaweed ingredient.
In other words, the “proof” of seaweed skincare benefits is elusive.
Still, what exists is promising and could point to numerous potential benefits, even if clear and wholly-convincing evidence isn’t available.
Acne is caused, in part, by the bacteria Propionibacterium acnes, or P. acnes. Seaweed may have anti-acne effects because of its antimicrobial properties.
Seaweed has been demonstrated to have strong antibacterial activity against several forms of bacteria.
One study screened 57 different seaweed species for anti bacterial properties against P. acnes specifically and found 15 to fight the acne-causing bacteria.
Several other studies have demonstrated the effectiveness of various seaweed species against P. acnes and Staph and other bacterial infections of the skin.
Hyperpigmentation, or skin darkening, is caused by an “abnormal accumulation of melanin pigments” in the skin.
Tyrosinase is an enzyme that plays an important role in this process, and tyrosinase inhibitors can thus help control hyperpigmentation.
Several species of seaweed have been shown to have tyrosinase inhibiting effects.
However, the majority of the research done on these properties have been done on animals or under the microscope, at cellular levels, and many compounds shown to have these tyrosine-inhibiting effects in-vitro (in the lab) have not had similar effects in-vivo (in humans).
As we age, the degradation of collagen and elastin in our skin lead to fine lines wrinkling.
It’s believed polysaccharides in seaweed can combat this degradation caused by collagenase and elastase.
Several studies in the lab have confirmed these activities — but few have been reproduced in humans.
One very small, double-blind study involving ten women compared the use of a brown seaweed (Fucus vesiculosus) extract with a placebo over a five week period.
The researchers found skin thickness and elasticity were improved, suggesting seaweed has hydrating, collagen producing and anti-aging benefits.
Numerous additional studies have been conducted on the active components within various types of seaweed.
These components — including various peptides, minerals and polyphenols — have shown variable levels of promise in the treatment of things like age spots, cellulite, inflammation, dry skin and protection from UV damage.
However, the majority of these studies have been conducted on individual substances derived from seaweed. What isn’t clear is how these substances react in the actual treatment of these conditions in humans.
Seaweed may be a safe addition to your skincare routine, and could provide numerous benefits. But there isn't solid, scientific evidence that can unequivocally prove it’s inclusion in skincare products will deliver those benefits across the board.
In the search for natural ingredients that really work in skin care, the lines can often be blurred by what actually works, and what we just think works.
Seaweed (or seaweed extracts, more specifically) is just one of those ingredients. It’s alleged to help everything from acne and aging, to hyperpigmentation and seemingly everything in between.
While the hard science surrounding seaweed is still thin, a lot of the current study results surrounding seaweed’s benefit to our skin is promising.
So, if you’re thinking about picking up that new seaweed-infused acne scrub, body bar or lotion you’ve been hearing about, it’s unlikely that it’ll hurt your skincare regimen, and may even do some good.
If you give seaweed a shot and find it’s not helping you as quickly as you’d like it to, your best bet is to consult with a certified dermatology practitioner to come up with a skincare regimen that really works for you.