Along rocky coastlines, beneath cold saltwater and rolling tides, enormous underwater forests sway with the movement of the sea. These are kelp forests, some of the most extraordinary ecosystems on Earth and home to one of the ocean’s most useful botanical treasures.
Sea kelp has been gathered and used by coastal cultures for centuries as food, fertilizer, and a source of nourishment for the skin and hair. Rich in naturally occurring minerals and unique marine compounds, kelp has also found its way into modern skincare, haircare, bath products, and wellness traditions.
While we often call kelp a plant, it is actually a type of large brown algae, primarily belonging to the order Laminariales. And although it grows beneath the waves rather than in an herb garden, kelp has certainly earned a place in the botanical apothecary.
What Is Sea Kelp?
Kelp is a broad term for several species of large brown seaweeds that grow primarily in cool, nutrient-rich coastal waters.
Depending on the species, kelp can grow remarkably quickly and form vast underwater forests. Some varieties reach tremendous lengths, creating complex marine habitats that shelter fish, invertebrates, sea mammals, and countless other organisms.
Common kelps include species belonging to genera such as Laminaria, Saccharina, and Macrocystis.
Kelp absorbs nutrients directly from the seawater surrounding it, which contributes to its naturally rich mineral composition.
The Nutritional Treasures of Kelp
Sea kelp contains a fascinating mixture of naturally occurring nutrients and marine compounds, including:
Iodine
Kelp is especially well known for iodine, an essential trace mineral the body requires to produce thyroid hormones.
Alginate
Alginates are polysaccharides found in the cell walls of brown algae. Their ability to bind water and create gels is one reason kelp-derived ingredients are commonly used in skincare, cosmetics, foods, and other products.
Fucoidan
This naturally occurring sulfated polysaccharide found in brown seaweed has attracted considerable scientific interest for its biological properties.
Fucoxanthin
Fucoxanthin is the brown-orange carotenoid pigment that gives many brown seaweeds their characteristic coloring. It is being studied for its antioxidant and other potential biological activities.
Kelp can also provide varying amounts of minerals such as calcium, magnesium, potassium and iron, depending on the species and growing conditions.
Sea Kelp & Thyroid Nutrition
Perhaps the most famous association with kelp is its iodine content.
The thyroid gland needs iodine to manufacture thyroid hormones, which help regulate processes including metabolism, growth and energy use.
However, kelp is a perfect example of why more is not always better.
The iodine concentration of seaweed can vary dramatically between species and even between individual products. Excessive iodine intake can interfere with normal thyroid function in susceptible people.
For that reason, kelp supplements should not be treated casually as an everyday source of iodine, particularly for people with thyroid conditions or those taking thyroid medications.
Using kelp as a culinary ingredient is different from taking highly concentrated supplements, but moderation still matters.
Sea Kelp for the Skin
Kelp has become a popular ingredient in botanical and marine-inspired skincare.
Its natural polysaccharides can help attract and retain moisture, making kelp extracts particularly appealing in products intended to leave skin feeling hydrated, soft, and conditioned.
You’ll find kelp or seaweed extracts in products such as:
● Facial masks and cleansers
● Moisturizers and serums
● Body creams
● Bath soaks
● Body wraps
● Scrubs
● Facial mists
Kelp-derived ingredients also contain naturally occurring antioxidant compounds. Antioxidants are valuable in cosmetic formulations because they can help protect against oxidative processes.
Rather than thinking of kelp as a miracle cure for skin conditions, it is better viewed as a mineral-rich, hydrating and conditioning cosmetic ingredient.
Sea Kelp for Hair & Scalp Care
The ocean has wandered into the haircare cabinet, too.
Kelp extracts can be incorporated into shampoos, conditioners, scalp treatments, masks, and botanical hair products.
Its polysaccharides and mineral-rich composition make it useful for formulations designed to condition the hair and support moisture retention.
Kelp can work particularly beautifully alongside ingredients such as:
Rosemary • Nettle • Horsetail • Aloe Vera • Jojoba • Argan Oil • Sea Salt
When formulating water-based products containing kelp, proper preservation is especially important. Botanical and marine ingredients do not naturally make a finished cosmetic microbiologically safe.
Kelp Baths & Body Care
Seaweed bathing has a long history in coastal wellness traditions, particularly in places where seaweed could be gathered directly from the shore.
Dried kelp or cosmetic-grade seaweed powders can be incorporated into bath products to create a wonderfully earthy, ocean-inspired experience.
A kelp bath pairs beautifully with sea salt, oats, lavender, rosemary, or other botanicals.
The result is less “tropical beach cocktail” and more wild shoreline after the tide rolls out, which has its own rugged charm.
Kelp in the Garden
Kelp’s usefulness doesn’t stop at the edge of the bathtub.
Seaweed has also been used agriculturally as a soil amendment and fertilizer.
Commercial kelp meal and kelp extracts are commonly used in gardening because they provide minerals and organic compounds to the soil. They can be incorporated into compost, garden beds, and certain plant-feeding preparations according to the product’s directions.
If gathering seaweed yourself, local harvesting regulations should always be checked first. Wild seaweed is an important part of coastal ecosystems and shouldn’t be stripped indiscriminately from shorelines.
Culinary Uses of Kelp
Humans have eaten seaweed for thousands of years.
Different types of kelp appear in soups, broths, seasonings, noodles, salads, and dried snacks.
One particularly well-known example is kombu, an edible kelp commonly used in Japanese cooking. Kombu is famously used to prepare dashi, where it contributes a deep savory flavor associated with naturally occurring glutamates.
Kelp can also be dried and ground into flakes or powders for culinary use.
Because its iodine concentration can be high and highly variable, however, eating very large quantities every day isn’t necessarily beneficial.
Traditional & Folk Uses
For coastal communities, seaweed was not an exotic superfood shipped in a glossy pouch. It was simply part of the landscape.
Different seaweeds have historically been used as:
Food • animal feed • fertilizer • bathing material • household material • sources of minerals
Seaweed traditions vary considerably by region, from Ireland and Scotland to Iceland, Japan, Korea, China and coastal Indigenous communities.
Those traditions remind us that herbalism doesn’t end where the soil meets the sea.
There is an entire apothecary beneath the water.
Sea Kelp in Folklore & Symbolism
The ocean has always occupied a peculiar place in folklore: simultaneously giver, destroyer, road, boundary, mystery, and home.
Seaweed naturally inherited some of that symbolism.
In modern spiritual and folk practices, kelp and other seaweeds may be associated with:
Protection
The sea as a cleansing boundary and protective force.
Prosperity & Abundance
Kelp forests grow thickly in favorable waters, making seaweed a fitting symbol of abundance.
Cleansing
Saltwater and sea plants are often incorporated symbolically into cleansing traditions.
Adaptability
Kelp survives powerful currents by bending with the water rather than remaining rigid.
Emotional Release
Ocean symbolism is frequently connected with releasing what has become stagnant and allowing it to be carried away.
These are cultural and spiritual associations rather than scientifically established effects, but they offer another fascinating way humans have built relationships with the natural world.
A Few Important Kelp Precautions
Natural does not automatically mean unlimited.
Kelp deserves particular respect because its iodine content can be extremely variable.
People with thyroid disorders, people taking thyroid medications, and those who are pregnant or breastfeeding should speak with an appropriate healthcare professional before taking concentrated kelp or iodine supplements.
Seaweed can also accumulate substances present in the surrounding seawater. This makes sourcing especially important.
For culinary, cosmetic, or herbal preparations, choose seaweed from reputable suppliers that appropriately test and source their products rather than collecting kelp from potentially polluted waterways.
And remember that kelp supplements and kelp-infused skincare are very different things. A cosmetic ingredient does not carry the same nutritional implications as consuming concentrated seaweed.
The Ocean’s Herbal Cabinet
We tend to picture herbalism in shades of woodland green: bundles of rosemary drying from rafters, jars of chamomile flowers, roots tucked into apothecary drawers.
But nature’s medicine cabinet is much larger.
Beyond the meadow lies the shoreline, and beyond the shoreline stretches a submerged forest.
Sea kelp is a beautiful meeting place between traditional foodways, modern cosmetic science, gardening, folklore, and botanical curiosity. It can nourish a bowl of broth, enrich a garden bed, lend moisture-loving compounds to skincare, and remind us that some of Earth’s most fascinating botanicals don’t grow beneath our feet.
They grow beneath the tide.
Educational information only. This article is not intended to diagnose, treat, cure, or prevent any disease. Consult an appropriate healthcare professional before using concentrated kelp or iodine supplements, particularly if you have a thyroid condition, take medication, or are pregnant or breastfeeding.