The Magic of Magnesium

A concentrated liquid magnesium soak works harder than a bag of Epsom salts — if you understand what's actually going on under the water. Here's the science, the formula, and how to use it.

In this article

1. Why most bath soaks don't do much
2. Magnesium 101: 300+ reactions, 50% deficient
3. Why through the skin beats a pill
4. Magnesium chloride vs. magnesium sulfate
5. Where the magnesium comes from: Zechstein
6. The terpene effect: plants as penetration enhancers
7. The three plants, and what each one does
8. What's inside the bottle
9. Why liquid replaces your Epsom salts
10. How to use it
11. When to reach for it
12. Where it fits in the Esker ritual
13. Frequently asked questions
14. The relaunch, briefly

Why most bath soaks don't do much

You run the water, tip in a scoop of something blue or pink, and get out fifteen minutes later feeling pleasant but not particularly different. If that's been your experience with bath soaks, the product isn't the only thing to blame. It's the chemistry.

Most bath salts on the market are some variation of magnesium sulfate — better known as Epsom salt. Epsom has been around since the 1600s. It makes the water feel a little softer. It smells like nothing. It may or may not be absorbed through the skin in any meaningful quantity — the research on sulfate-based transdermal absorption is limited and mixed.

The Magnesium Bath Enhancer is a different kind of product. It's a concentrated liquid made with magnesium chloride (a form the skin takes up far more efficiently than sulfate), paired with a blend of naturally occurring plant terpenes that help carry the minerals deeper through the skin barrier.

Four to six pumps in a full tub. Instant dissolve. No gritty residue. You smell eucalyptus, lavender, and palo santo when the steam rises. You get out feeling like you actually soaked.

"Magnesium chloride + terpenes is what makes a bath soak do something. Sulfate alone, in most cases, does not."

Magnesium 101: 300+ reactions, 50% deficient

Magnesium is an essential mineral involved in more than 300 biochemical reactions in the body — including muscle contraction, nerve function, blood pressure regulation, energy production, bone health, sleep, and the stress response. It is, by almost any measure, one of the minerals your body needs the most of and gets the least of.

Estimates from the USDA and NIH suggest roughly half of Americans are not meeting the recommended daily intake of magnesium. The usual culprits: modern soil depletion, processed food, caffeine, alcohol, high stress, and medications that interfere with absorption.

Symptoms of low magnesium are quiet but familiar — muscle cramps, twitching eyelids, restless sleep, mild anxiety, sugar cravings, fatigue that coffee doesn't touch. Most people have felt some of them without connecting the dots.

You can get magnesium from food (pumpkin seeds, almonds, spinach, dark chocolate), from supplements, or through the skin. The skin route is the one most people have never tried — and it's the route this bath is built for.

Why through the skin beats a pill

Oral magnesium supplements have a real job in a real deficiency. But they have two limitations worth knowing.

Absorption is variable. Depending on the form (citrate, oxide, glycinate, threonate) and the state of your digestion, studies suggest as little as 20–50% of the magnesium you swallow actually gets absorbed into the bloodstream. The rest passes through.

GI side effects are common. Magnesium is what's in most gentle laxatives for a reason. High doses — or even moderate doses in sensitive people — can cause cramping, bloating, and loose stools. It's one of the top reasons people quit magnesium supplements within a few weeks.

Your skin is different. It's the body's largest organ, and in certain forms and delivery systems, it offers a direct route for minerals to enter the bloodstream — bypassing the digestive tract entirely. That's transdermal absorption. And when the mineral is magnesium chloride dissolved in warm water and carried by plant terpenes that help it cross the skin barrier, the route gets even more efficient.

Transdermal magnesium isn't a replacement for oral magnesium in a clinical deficiency. It's a daily-to-weekly supplement strategy that gets magnesium into your system without the GI tradeoffs — and it's the one most backed up by the people who live in a bathtub every week.

Magnesium chloride vs. magnesium sulfate

If you take only one thing away from this piece, take this: not all magnesium is the same mineral for the skin.

Magnesium chloride is the form most often recommended by the research on transdermal magnesium — including the work done by the late Dr. Norman Shealy, who helped popularize the topical approach. It's why spa brands that take bath chemistry seriously tend to default to chloride over sulfate.

Where the magnesium comes from: Zechstein

Our magnesium chloride is sourced from the Zechstein Sea, a 250-million-year-old underground seabed 1,600 meters beneath the surface in the Netherlands. The sea evaporated during the Permian period and was buried under layers of rock and clay, which means the magnesium deposited there has been sealed off from modern industrial pollution, heavy metals, and runoff for a quarter of a billion years.

The Zechstein name is a quality floor, not a marketing flourish. It's the reference source most topical-magnesium researchers cite when they mean "clean, highly bioavailable magnesium chloride." We use it because it's the best available mineral — and because a concentrated bath soak is only as good as the magnesium you start with.

The terpene effect: plants as penetration enhancers

Here's the part of the formula that's doing more work than most people realize.

Terpenes are the aromatic compounds plants produce — the reason eucalyptus smells like eucalyptus, the reason lavender smells like lavender, the reason a walk through a palo santo grove smells like nothing else. They are also, when applied topically in the right concentration, natural penetration enhancers: compounds that temporarily and reversibly help other molecules cross the skin barrier more efficiently.

The skin's outermost layer, the stratum corneum, is a good barrier — it's supposed to be a good barrier. Terpenes briefly loosen the lipid packing in that layer, letting small water-soluble molecules (like magnesium chloride) slip through more readily, and then the barrier resumes normal function.

This is the mechanism that makes the Bath Enhancer feel different from a scoop of Epsom. You're not just sitting in mineral water. You're sitting in mineral water with a built-in delivery vehicle.

Getting the terpenes to stay stable inside a highly concentrated magnesium chloride solution was the single hardest part of the nearly two-year reformulation. Concentrated magnesium chloride is hygroscopic and reactive — it does not want to share a bottle with a delicate essential oil blend. Cracking that stability problem is what made the relaunch possible.

The three plants, and what each one does

The terpene blend in the Bath Enhancer is built from three essential oils — each chosen for a specific physiological and sensory role.

Eucalyptus

What it does: anti-inflammatory, with respiratory-system benefits. The 1,8-cineole in eucalyptus opens up the airways, cools the breath, and gives the bath its "first inhale" clarity — the moment the steam rises and your sinuses let go.

Lavender

What it does: nervous-system regulation. Linalool and linalyl acetate, the two dominant compounds in lavender oil, have been shown in multiple controlled studies to reduce heart rate, lower cortisol, and promote parasympathetic (rest-and-digest) activity. It's the compound doing the work when a lavender bath actually puts you to sleep instead of just smelling nice.

Palo Santo

What it does: adaptogenic stress-response support. Palo santo contains limonene and α-terpineol — compounds associated in traditional use and emerging research with grounding, mood regulation, and mental reset. It's what gives the bath its signature Esker aroma: warm, woody, softly sweet, unmistakable.

Eucalyptus opens you up. Lavender calms you down. Palo santo grounds the whole ritual. All three, together, also do the penetration-enhancement work that makes the magnesium more available to your skin.

What's inside the bottle

Every ingredient in the formula has a specific role. Nothing is filler.

Clean, plant-based, dye-free. No synthetic fragrance, no sulfates, no parabens, no phthalates.

Why liquid replaces your Epsom salts

The format of a bath product is not a small detail. It changes how often you actually use it.

Epsom salts come in heavy bags. You measure one to two cups into the water. You wait for them to dissolve. You rinse off the gritty film that settles on your skin and the ring that settles on your tub. You restock the bag every few months.

The Bath Enhancer comes in a bottle. You shake it once. You pump four to six times into the running water. It dissolves instantly. There's no film, no ring, no measurement. The bottle travels. The bottle lasts.

Four to six pumps equals the magnesium dose of two full cups of traditional Epsom — in a delivery system that actually absorbs.

How to use it

1. Shake well. The concentrated formula separates between uses — a quick shake re-suspends the terpenes and the mineral.
2. Pump 4–6 times into the bath. Works in hot water for muscle recovery and wind-down. Works in cold water for post-workout recovery and circulation.
3. Soak 15–20 minutes. Long enough for the heat, the scent, and the minerals to do their work. Short enough that the water is still warm when you get out.
4. Rinse if you want to — or don't. The formula rinses clean; no residue either way. Follow with Esker Body Oil or Firming Body Oil to lock in the softened state.

When to reach for it

A few real scenarios, not a lifestyle fantasy:

• Pre-bed wind-down. When sleep has been short or restless for a stretch. Lavender is doing the heavy lifting here, plus the temperature drop after a hot bath is one of the most reliable natural sleep signals the body has.
• Post-workout recovery. After a hard run, a heavy lift, or a long hike. Magnesium chloride supports muscle recovery and helps calm the lactic-acid-tired feeling in your legs. Works in cold water for athletes who prefer cold recovery.
• Stress reset. After a week of bad news, conflict, or cortisol-fuelled caffeine loops. Palo santo's adaptogenic profile and lavender's nervous-system effect are the combination here.
• Post-travel. Plane air, airport stress, late meals, disrupted sleep. One bath and your nervous system remembers what a home feels like.
• Mid-cycle or PMS. Magnesium is one of the most-cited nutrients for menstrual cramping, tension, and mood regulation. A soak two or three nights in a row can be a real protocol.
• Just because it's Sunday. A weekly reset beats a monthly emergency every time.

Where it fits in the Esker ritual

Esker's four-step framework is Cleanse → Exfoliate → Nourish → Elevate. 

A full at-home spa stack looks like this:

1. Cleanse. Rinse off the day in a hot shower.
2. Exfoliate. Dry brush or body plane the skin before you get in the tub. This is the step most people skip, and it's the one that unlocks everything the bath is going to deliver.
3. Nourish. Pump 4–6 times of the Bath Enhancer into a full tub. Soak 15–20 minutes. The terpenes carry the magnesium; the heat handles the rest.
4. Elevate. Towel off. Apply Esker Body Oil or Firming Body Oil while the skin is still warm and slightly damp. The oil locks in the softened, mineralized state — and it's the finish that keeps the ritual going into the next day.

Frequently asked questions

Does it really work in cold water?

Yes. The liquid formula was specifically made to dissolve instantly in water of any temperature — it's one of the reasons we reformulated. Cold-plunge enthusiasts and post-workout cold-bath users get the same mineral delivery as hot-bath users. The scent is more subtle in cold water; the mineral effect is the same.

How is this different from Epsom salts?

Two things. First, the form of magnesium — chloride (what we use) absorbs through the skin far more efficiently than sulfate (what Epsom is). Second, the terpene blend — the plant compounds in our formula help carry magnesium deeper through the skin barrier, a mechanism Epsom doesn't have. Practically, 4–6 pumps of liquid replaces 1–2 cups of salt, with no residue and no wait time.

How often can I use it?

As often as you like. Nightly is fine. Many customers settle into a 2–3 times per week rhythm; athletes and high-stress users often go daily. The formula is gentle enough for regular use; the magnesium effect is cumulative.

Is it safe for sensitive skin?

It's clean, plant-based, dye-free, and free of synthetic fragrance. The formula is gentle. If you have a known sensitivity to essential oils (particularly eucalyptus or palo santo), patch-test a small area first — as you would with any new bath product.

Can I use it during pregnancy?

Please consult your OB or midwife first. Essential oils are a category that individual providers have individual views on, and pregnancy is the right time to ask your own doctor rather than take a generic internet answer.

Is it safe for children?

For children under 12, we recommend checking with your pediatrician on essential oil exposure, and using a reduced dose (2–3 pumps in a smaller tub) if cleared.

Will it stain my tub?

No. The formula pours clear and rinses clean. The amber glass bottle protects the oils from light; it's an inside-the-bottle choice, not an outside-the-tub one.

How long does one bottle last?

At 4–6 pumps per bath, a bottle is roughly 25–35 baths, depending on your dose. Twice a week, that's three to four months per bottle.

How should I store it?

Room temperature, out of direct sunlight. The amber bottle handles most of the light protection. Keep the cap on; shake before each use.

What's the difference between this and a bath oil or bubble bath?

A bath oil softens the water and moisturizes. A bubble bath makes bubbles and smells nice. The Magnesium Bath Enhancer is a mineral therapy — it's delivering a nutrient your body uses, through the most direct delivery system your body has.

The relaunch, briefly

The first version of this product launched in 2023 as the first liquid magnesium soak designed for both hot and cold water. It sold out the first time we made it, and every subsequent time we made it. The formula worked beautifully in the tub — but the chemistry of a highly concentrated, first-of-its-kind magnesium chloride liquid was genuinely hard to keep stable in the bottle. We couldn't scale it without compromising what made it special.

So we pulled it and went back to the lab for nearly two years. The goal was to stabilize the formula without diluting it — to keep the concentration, keep the transdermal absorption, keep the experience. The breakthrough was figuring out how to get the terpenes and the concentrated magnesium chloride to coexist in a shelf-stable form. What's on the shelf now is more consistent, more stable, and every bit as effective as the version that kept selling out — actually, more so.

If you want the longer version of that story, we wrote it up here.

Source notes

Zechstein magnesium chloride is sourced from the Zechstein Sea in the Netherlands. The Magnesium Bath Enhancer is a clean, plant-based, dye-free formula built on magnesium chloride, sea salt, eucalyptus, lavender, palo santo, and naturally occurring terpenes. Esker Beauty has been featured in TODAY, Vogue, Allure, and the Esquire Grooming Awards, and used by Four Seasons and Canyon Ranch spas. Magnesium statistics (300+ biochemical reactions, ~50% of Americans below recommended intake) reflect commonly cited USDA and NIH figures. Research on transdermal magnesium absorption and on terpenes as penetration enhancers is an active area — nothing in this piece is a medical claim, and nothing here is a substitute for advice from your own doctor.