Magnesium Chloride

Overview

Magnesium chloride is a mineral salt most commonly sourced from seawater evaporation or underground brine deposits. It dissolves in water with almost enthusiastic ease — it is one of the most soluble magnesium compounds available, which is exactly why it has become the backbone of “magnesium oil” products. (Worth clarifying: magnesium oil is not actually an oil. It is a concentrated aqueous solution of magnesium chloride that feels oily and slippery on skin due to the high salt concentration.)

The interest in topical magnesium has grown steadily as people look for ways to supplement magnesium through the skin rather than the gut. While the scientific evidence for transdermal magnesium absorption is still evolving, anecdotal reports of improved sleep, reduced muscle cramps, and less restless-leg discomfort have made magnesium sprays and bath soaks genuinely popular.

Magnesium chloride is also hygroscopic — it aggressively attracts moisture from the air. This is important for both formulation (it keeps skin feeling hydrated) and packaging (it turns into a puddle if left uncovered in a humid room).

What it does in a formula

In topical sprays and bath soaks, magnesium chloride delivers magnesium ions to the skin surface. Whether those ions penetrate deep enough to raise systemic magnesium levels is debated, but localized effects — muscle relaxation, reduced tension, skin hydration from the hygroscopic salt — are consistently reported by users.

In deodorant formulations, magnesium chloride creates a mineral-rich environment on the skin surface that is less hospitable to odor-causing bacteria. It is an increasingly popular active in “natural” deodorant sticks and sprays, either as a primary active or alongside zinc ricinoleate and arrowroot powder.

The hygroscopic nature also means it acts as a humectant in leave-on products — it draws moisture to the skin surface. At high concentrations, though, this can feel sticky.

How to use

Magnesium spray (“magnesium oil”): Dissolve 30-50% magnesium chloride flakes in distilled water. That is it — no emulsifier needed. The solution is self-preserving at these high concentrations due to low water activity. Spray on legs, feet, or shoulders after a shower. It may tingle on freshly shaved skin — this is normal and fades in minutes.

Bath soaks: Use 100-300 g of flakes per bath (roughly 1-2 cups). Can be blended with Epsom salt, essential oils, or dried botanicals.

Deodorant sprays: 10-20% in distilled water with optional aloe vera (2-5%), witch hazel (10-20%), and a few drops of essential oil.

Lotions and creams: 5-10% in the water phase. Higher percentages can destabilize emulsions, so test stability carefully. Keep the formula pH within 6-8 for best skin compatibility.

The flakes dissolve readily in room-temperature water — no heat required.

Best for / Worst for

Best for: magnesium sprays, bath soaks, foot soaks, muscle-recovery products, natural deodorants, sleep-ritual body products, post-workout sprays.

Worst for: facial products (the tingling sensation is unwelcome on the face), products for broken or freshly shaved skin (stings), emulsions above 10% (stability risk), anhydrous products (it needs water to dissolve and function).

Common pitfalls

Not warning users about the tingle. First-time users of magnesium spray often panic at the tingling or slight stinging sensation. This is normal — it is the magnesium ions interacting with skin, and it usually diminishes with regular use. Include clear usage instructions.

Storing flakes in open containers. Magnesium chloride is so hygroscopic that it will absorb enough atmospheric moisture to partially dissolve itself. Store flakes in airtight containers, and package finished bath soak blends in sealed bags.

Using too much in emulsions. Above 10% in a lotion, magnesium chloride can break emulsions, cause graininess, or create an uncomfortably sticky finish. If you want high-concentration delivery, a spray is a better format than a cream.

Confusing it with Epsom salt (magnesium sulfate). They are both magnesium salts, but they behave differently. Magnesium chloride is significantly more soluble, more hygroscopic, and is generally considered to have better transdermal bioavailability. They are not interchangeable in formulas.

Skipping pH testing. At high concentrations, magnesium chloride solutions can drift slightly acidic. Check pH and adjust if needed — aim for 6-8 on skin products.

Substitutes

• Epsom salt (magnesium sulfate) — the classic bath soak mineral. Less soluble, less hygroscopic, different ion profile. Better for scrubs, worse for sprays.
• Magnesium hydroxide — the active in milk of magnesia. Used in deodorants as an odor-neutralizing alkaline mineral. Not a direct swap for bath soak applications.
• Dead Sea salt — a complex mineral blend including magnesium chloride, potassium chloride, and sodium chloride. Broader mineral profile, less concentrated magnesium delivery.
• Zinc ricinoleate — in deodorant formulas specifically, this is a complementary odor-absorbing ingredient rather than a direct substitute.