Seaweed Baths and Seaweed Skincare: What the Evidence Says, and How to Run One at Home

By Jayson Byles, forager & chef · September 2026

A seaweed bath is a warm bath with fresh wrack in it, the oldest form of seaweed skincare and the one people ask us about most; seaweed skincare more broadly means extracts of brown, red or green seaweed used in creams, masks, cleansers and oils for the polysaccharides, polyphenols and pigments they carry. The evidence for what they do on skin is mostly laboratory work, with a handful of small human trials, most run by the companies selling the extract. We cut the same wracks and kelps on the Fife shore that go into those jars, so this page starts with the bath, how to run one at home with a bag of bladderwrack and what the evidence says it does, then works through what the jars contain and what the trials show.

Seaweed baths: the tradition and the evidence

The seaweed bath is older than the cream. The French coined the word thalassotherapy in 1867, and in 1899 Louis Bagot opened the first marine institute at Roscoff in Brittany, treating rheumatism with heated seawater. Ireland used the weed itself: around 1900 there were an estimated 300 seaweed bath houses in Ireland, nine in County Sligo, and the Strandhill baths of 1912 were revived by the Walton family in 2000 as Voya. Their bath seaweeds are serrated wrack and bladderwrack, the two Fucus species that carpet the Fife mid-shore. On the Scottish side, ishga has hand-cut serrated wrack, bladderwrack, channel wrack and egg wrack on the Isle of Lewis since 2013 and was grand champion at the 2025 Natural Health Beauty Awards; in Margate, Haeckels, founded in 2012 and now trading as Dulcie, built a brand on beach-gathered weed.

What does a seaweed bath do? Separate the water from the weed. A 2025 trial in Korea put 58 women through twice-weekly 20-minute hot-spring baths for 16 weeks and measured better skin hydration, lower water loss through the skin and lower self-reported stress than in controls; mineral water, no seaweed. A 2025 systematic review of seawater therapy for atopic dermatitis found ten studies and moderate-quality evidence that Dead Sea and thermal-water bathing eases severity; again, no seaweed. We could not find a controlled trial of a seaweed bath as such. So the honest claim is this: a warm mineral bath has some evidence behind it, wrack releases a slippery alginate and fucoidan gel that leaves skin feeling soft, and the rest is tradition and pleasure. That is enough for us.

A seaweed bath at home with Fife wrack

You need a modest bagful of fresh wrack, cut not pulled, from a clean shore. A bathful for yourself is personal use and needs no licence on Crown foreshore in Scotland (Crown Estate Scotland sets out where commercial harvesting begins); our plain guide to the law and why we cut, never pull cover the manners. Pick a shore away from outfalls and harbours, and use the tide planner to cut on a falling tide.

1. Cut a mixed bag of bladderwrack and serrated wrack, about two double handfuls, from the middle shore, leaving the holdfast and lower frond on the rock.
2. Rinse it in clean seawater on the shore to shift sand and small animals, then under a cold tap at home. Do not scrub; the gel you want is on the surface.
3. Run a warm bath and put the wrack straight in, or in a muslin bag if you dislike fronds against your skin. Warm water draws the gel out within minutes and turns amber.
4. Soak for 20 to 30 minutes. Rub a frond over the skin if you like; that is where the softness comes from.
5. Rinse off, or leave the film on and pat dry. Lift the weed out before you drain the bath and put it on the compost or round the roses: our page on seaweed in the garden explains why gardeners want it.

Plain cautions. Keep the water warm rather than hot; if you are pregnant, have a heart condition or a skin condition that flares with heat, ask your midwife or GP first; patch-test if you react to new products; and do not eat the bath weed. Wrack is not a medicine, and we make no claim for the bath beyond the ones a warm bath earns for itself.

What seaweed puts in a cream

A 2021 review in Marine Drugs on seaweed compounds in cosmetics sorts the ingredients into families.

• Alginate, carrageenan and ulvan. The gel-forming sugars of the browns, the red carrageen and the green sea lettuce. They thicken, hold water on the skin and set face masks: the oldest and least controversial use, and the one growing fastest as formulators replace acrylic thickeners.
• Fucoidan. The sulphated sugar of the browns, in the wracks, sugar kelp and oarweed. Sold on soothing, brightening and anti-ageing results; see the trials below.
• Phlorotannins. The polyphenols that make bladderwrack bitter. Antioxidant in the test tube and inhibitors of tyrosinase, the pigment enzyme, in cells. Human data is thin.
• Fucoxanthin. The brown pigment; antioxidant and photoprotective in cell and animal work.
• Mycosporine-like amino acids. The UV-absorbing molecules red seaweeds make for themselves; dulse is a rich source. Already used as natural sunscreen actives, and a 2024 French study of dulse found one of them, usujirene, rising from 9 to 24 per cent of the total under UV: the plant putting on sunscreen.

Is seaweed good for your skin? What the human trials show

A 2021 review in the Journal of Clinical and Aesthetic Dermatology went looking for clinical studies of seaweed extracts on skin and found eight, of 10 to 90 people: four on moisturising, two on pigmentation and wrinkles, two on cellulite. The authors concluded that the studies to date show moisturising, pigment-lightening and slimming effects from topical extracts, and that further research is needed on long-term safety, efficacy and dose. That is the honest ceiling: real but small, short and few.

Two of those trials involve the plant we cut. In 2002 scientists at the Japanese cosmetics firm Kao applied a gel with 1 per cent Fucus vesiculosus extract to volunteers’ cheeks twice a day for five weeks and measured a small decrease in skin thickness by ultrasound and an improvement in elasticity; the number of subjects is not given in the abstract. In 2015 the Tasmanian fucoidan maker Marinova published split-face studies of two fucoidan-rich extracts, one from Undaria and one from bladderwrack, in around 20 people each, reporting soothing, shallower wrinkles, brighter skin and lighter age spots. Small human trials, company-run, without independent replication.

For the rest of the ingredient list the evidence sits a rung lower. A 2024 review of the brown seaweed Sargassum in dermocosmetics counted study types across 17 species: 82 per cent cell or test-tube work, 8 per cent clinical. That ratio is about right for seaweed skincare as a whole. When a label says “clinically proven”, ask: in how many people, for how long, and paid for by whom?

Seaweed for eczema?

This is the question we are asked most, and the answer is a careful no. The NHS treatments for atopic eczema are emollients and topical steroids, with dressings and prescription medicines for severe cases. The bathing evidence above is for seawater and thermal water, not seaweed, and there is no clinical trial of a seaweed product in eczema that we could find. A cosmetic that claims to treat, relieve or prevent eczema is making a medicinal claim, which under the medicines regulator’s guidance on what is a medicinal product turns it into an unlicensed medicine by presentation. If a seaweed cream feels comfortable on your skin, that is a fair reason to use it; expecting it to treat a condition is not.

Making your own: the rules for small makers

People go home from a workshop wanting to make a wrack face mask or bath soak to sell at a market. It can be done, but a cosmetic sold in Great Britain is regulated whatever its size. The UK Cosmetics Regulation requires a UK-based responsible person, a cosmetic product safety report signed by a qualified assessor, a product information file kept for ten years, notification on the Submit Cosmetic Product Notification portal before sale, and a label with INCI ingredient names, batch number and durability. Every claim on the pack must meet the six common criteria for cosmetic claims: legal compliance, truthfulness, evidential support, honesty, fairness and informed decision-making. “Moisturising” can be supported; “heals” cannot be said at all.

The raw material is the part we can help with. A safety assessor will ask for the species by Latin name, the shore, the harvest date and how the plant was rinsed and dried. We cut identified wrack, kelp, carrageen and dulse to order, fresh or dried, with the shore and date on every bag; testing and a certificate of analysis are available on request. The commercial supply page has the forms and quantities, and our seaweed nutraceuticals page lists what each species carries.

What the research says now

Developments from 2023 onwards that matter for seaweed in skincare, each with its evidence level.

• Dulse sunscreen molecules, 2024. The French cultivation study above showed usujirene rising under UV in Palmaria palmata, a natural filter a red seaweed farm could be tuned to produce. Laboratory and culture work.
• Sargassum in dermocosmetics, 2024. The review of 17 species: 82 per cent of studies in vitro, 8 per cent clinical. A map of how thin the human evidence is.
• Seaweed thickeners replacing acrylics, 2025. The ingredient company Origin by Ocean set out alginate-based systems for creams, serums and cleansers in place of acrylate thickeners, made from invasive Sargassum. A company statement, but a real direction: texture, not actives, is where seaweed is most likely to reach every bathroom.
• Repeated bathing and the skin barrier, 2025. The 16-week Korean spa trial, 58 women, hot-spring water. Controlled, not randomised; no seaweed.
• Seawater and atopic dermatitis, 2025. The systematic review of ten studies, four randomised, with moderate-quality evidence for seawater and thermal bathing. No seaweed.
• Fucoidan and alginate as biomaterials, 2026. A review in Frontiers in Plant Science of the two brown-seaweed sugars in wound dressings, hydrogels and delivery systems. Established use for alginate dressings; laboratory and animal work for the rest. The medical end is on our seaweed in medicine page.

Our reading of the evidence is that seaweed earns its place in skincare as a texture, a humectant and a pleasure, with a few small trials suggesting more; anyone who says it does more should show you the trial. The wracks the Irish bath houses filled with, and that Lewis and Margate built brands on, grow thick on our rocks. The wider picture is in the other uses of seaweed, the kelp trade is on the history page, and the shore itself is in the complete guide to seaweed foraging in Scotland.

Sources

The figures and findings above come from these sources; the research papers are open access where a PMC or Frontiers link is given.

• Applying seaweed compounds in cosmetics, cosmeceuticals and nutricosmetics (Marine Drugs, 2021)
• Clinical studies of the safety and efficacy of macroalgae extracts in cosmeceuticals. Murphy & Dow (Journal of Clinical and Aesthetic Dermatology, 2021)
• Treatment of human skin with an extract of Fucus vesiculosus changes its thickness and mechanical properties. Fujimura et al. (Journal of Cosmetic Science, 2002)
• Topical benefits of two fucoidan-rich extracts from marine macroalgae. Fitton et al. (Cosmetics, 2015)
• Dermocosmetic properties of bioproducts from Sargassum macroalgae (Frontiers in Marine Science, 2024)
• Mycosporine-like amino acids in Palmaria palmata: specific implication of usujirene in photoprotection (Marine Drugs, 2024)
• Effects of repeated balneotherapy on skin hydration and psychophysiological stress: a 16-week Korean spa trial (International Journal of Biometeorology, 2025)
• Efficacy and safety of seawater therapy versus non-pharmacological interventions for atopic dermatitis: a systematic review (Cureus, 2025)
• Fucoidan and alginate from brown seaweeds: extraction, structure and biomedical applications (Frontiers in Plant Science, 2026)
• Rethinking beauty: how ocean innovation can replace synthetic polymers (Origin by Ocean, July 2025)
• The role of the Roc’h Roum marine institute at Roscoff in the history of thermalism (Roscoff Tourisme chronicles)
• About Voya Seaweed Baths, Strandhill (Voya)
• About us (ishga, Isle of Lewis)
• Awards (ishga, 2024 to 2025)
• About Dulcie, formerly Haeckels (Dulcie, Margate)
• Licensing of wild seaweed harvesting (Crown Estate Scotland)
• Atopic eczema: treatment (NHS)
• A guide to what is a medicinal product, Guidance Note 8 (MHRA)
• Regulation 1223/2009 and the Cosmetic Products Enforcement Regulations 2013: Great Britain (Office for Product Safety and Standards, updated 2023)
• Commission Regulation (EU) No 655/2013 laying down common criteria for the justification of claims used in relation to cosmetic products (retained UK law, legislation.gov.uk)

Questions we get asked

What are the benefits of a seaweed bath?

Warm bathing itself has some evidence: a 2025 trial found better skin hydration and less stress after 16 weeks of hot-spring baths. Wrack adds a slippery alginate and fucoidan gel that leaves skin feeling soft. We found no controlled trial of a seaweed bath as such, so enjoy it as a tradition with a plausible mechanism, not a treatment.

Which seaweed do you use for a bath?

Bladderwrack and serrated wrack, the two Fucus species of the middle shore. They are the traditional Irish bath seaweeds and the ones Scottish skincare makers cut, and they release their gel readily in warm water. Cut a modest bagful rather than pulling it, rinse in seawater, and put it in the bath whole or in a muslin bag.

Is seaweed good for your skin?

The evidence is modest and real. A 2021 review found eight human trials of seaweed extracts, of 10 to 90 people, showing moisturising, pigment-lightening and cellulite effects; most were short and company-run. Seaweed sugars are well established as thickeners and humectants. Claims beyond that rest on cell and animal studies, so treat them as promising rather than proven.

Can I use seaweed for eczema?

Not as a treatment. NHS care for atopic eczema is emollients and topical steroids, with prescription medicines for severe cases. The bathing studies that help are of seawater and thermal water, not seaweed, and any cosmetic claiming to treat eczema is making an unlawful medicinal claim. If a seaweed product feels comfortable on your skin, use it for that reason only.

Can I sell a seaweed face mask I make at home?

Only as a regulated cosmetic. In Great Britain you need a UK responsible person, a signed cosmetic product safety report, a product information file, notification on the Submit Cosmetic Product Notification portal before sale, and compliant labelling. Every claim must meet the six common criteria; moisturising can be supported, healing cannot be claimed. Identified, traceable raw material makes the safety assessment easier.

This page is general information, not medical or regulatory advice. Seaweed products are cosmetics or foods, not medicines; for a skin condition see a GP or pharmacist, and for a product you intend to sell take advice from a cosmetic safety assessor.