Hempz Beauty Actives Serene Waters is sold as a “Soothing & Relaxing Magnesium Body Lotion,” but on its own INCI list the magnesium — listed as Magnesium Sulfate, which is Epsom salt — appears at position 16, below water, two silicone-and-emollient skin-feel agents, fragrance and eleven others. The name is on the front; the mineral is well down the back.
Walk any drugstore body-lotion aisle and one bottle keeps its promise right in the product name: Hempz Beauty Actives Serene Waters Body Moisturizer with Magnesium, 17 fl oz for around $19.99. The brand subtitles it “Soothing & Relaxing Magnesium Body Lotion” and calls out “Magnesium & Arnica” as the key ingredients that “help replenish moisture and soothe.” Magnesium lotion for calm is having a moment — NPR covered the trend in September 2025 and cited one estimate putting the 2024 topical-magnesium market north of $400 million. So it is a fair question to ask the label: where is the magnesium, actually?
What does the Serene Waters ingredient list actually say?
Here is the full INCI list, quoted verbatim. Source: the Ulta product listing for Serene Waters Body Moisturizer with Magnesium (ulta.com), page fetched 2026-09-22. The same list appears on the brand’s own hempz.com page and the major-retailer listing — three sources in agreement.
Water/Aqua/Eau, Isopropyl Palmitate, Butylene Glycol, Propanediol, Fragrance (Parfum), Cetyl Alcohol, Glycerin, Dimethicone, Sorbitan Stearate, Butyrospermum Parkii (Shea) Butter, Stearic Acid, Glyceryl Stearate, PEG-100 Stearate, Cetearyl Alcohol, Cannabis Sativa Seed Oil, Magnesium Sulfate, Lavandula Angustifolia (Lavender) Oil, Aloe Barbadensis Leaf Juice, Panthenol, Arnica Montana Flower Extract, Phenoxyethanol, Polysorbate 40, Aminomethyl Propanol, Acrylates/C10-30 Alkyl Acrylate Crosspolymer, Nylon-12, Xanthan Gum, Ethylhexylglycerin, Chlorphenesin, Hexamethylindanopyran, Trisodium Ethylenediamine Disuccinate, Tetramethyl Acetyloctahydronaphthalenes, Linalyl Acetate, Hydroxycitronellal, Geranyl Acetate, Pinene, Alpha-Isomethyl Ionone, Terpineol, Citral, Isoeugenyl Acetate, Ascorbic Acid, Calcium Pantothenate, Potassium Chloride, Tocopheryl Acetate, Citric Acid, Potassium Sorbate, Benzoic Acid, Sodium Benzoate, Sorbic Acid, Rose Ketones, Linalool, Limonene.
INCI lists are ordered by concentration down to 1%, so position is a rough proxy for how much of something is in the pot. Count from the top and the marketed hero, Magnesium Sulfate, lands at position 16. Everything above it — the water base, isopropyl palmitate and the glycols, the fragrance, cetyl alcohol, glycerin, dimethicone, the shea and the emulsifier stack — is present in greater quantity than the magnesium the bottle is named after.
Where does the magnesium actually sit — and what is it?
Two details are worth saying plainly. First, the magnesium here is Magnesium Sulfate, which is the chemical name for Epsom salt — the same compound sold as a bath soak for a few dollars a bag. It is not a novel, patented, better-absorbed form of magnesium. Second, it is listed at position 16, one slot below Cannabis Sativa Seed Oil (the hemp-seed oil the brand is known for) and above Lavender Oil and the preservatives.
The other headlined active, Arnica Montana Flower Extract, is called out on the product page as a key ingredient too. It appears at position 20 — four spots behind the magnesium, and behind the preservative-and-thickener machinery that makes a lotion a lotion. Both of the actives on the front of the bottle are deep in the second half of the list.
This is the whole trick of reading an INCI list: the front of the bottle chooses the story, and the back of the bottle tells you the order. When the two disagree, the order is the one with the receipts.
Does magnesium at position 16 even matter for absorption?
Here is where the label question meets the evidence question, and honestly the evidence is thin either way. The idea behind “calming” magnesium lotion is that magnesium crosses the skin and does something systemic — relaxation, sleep, sore muscles. The published record does not really support that.
The outermost skin layer, the stratum corneum, is oily and repels water-loving, charged molecules. Magnesium in solution is an ion (Mg²⁺), and in its hydrated form it is bulky and struggles to passively diffuse through intact skin. A 2017 review in Nutrients (Gröber et al., “Myth or Reality—Transdermal Magnesium?”, DOI: 10.3390/nu9080813, PMC5579607) concluded that the case for transdermal magnesium is, in their words, scientifically unsupported, with hair follicles and sweat glands — roughly 0.1–1% of the skin’s surface — as the only real route in.
Even the most favorable human trial is small. A 2017 pilot RCT in PLoS ONE (Kass et al., DOI: 10.1371/journal.pone.0174817) tested a 56 mg/day magnesium cream in 25 people over two weeks and found no statistically significant change in serum or urinary magnesium for the group as a whole (p = 0.29 for serum). Only a subgroup reached significance, and the authors themselves called it a pilot that needs replication at higher doses. When NPR covered the trend, dermatologist Nicholas Theodosakis put the main risk succinctly: except in the pocketbook.
None of that means the lotion is bad at being a lotion — there is glycerin, shea butter and dimethicone up top, and those genuinely moisturize. It means the specific promise the name leans on, magnesium doing something calming through your skin, rests on small and mostly non-significant studies. If you want a fuller walk-through of that literature, Evil Goods (the team behind this site — we say so openly) collected it here: Does Magnesium Lotion Work?, on the Evil Goods blog.
How should you read a “magnesium” lotion label?
You do not need a chemistry degree, just a rule: find the hero ingredient from the front of the bottle in the list on the back, and see how far down it is. Anything named a “magnesium lotion,” “vitamin C serum” or “retinol cream” is making a claim you can check against its own INCI in ten seconds.
- The name on the front
- Serene Waters “Soothing & Relaxing Magnesium Body Lotion” — magnesium and arnica marketed as the key ingredients.
- The magnesium on the back
- Magnesium Sulfate (Epsom salt), position 16 of ~49, below fragrance, dimethicone and the emollient stack.
- The second active on the back
- Arnica Montana Flower Extract, position 20, behind the preservatives.
- The evidence
- Transdermal magnesium absorption is supported mainly by small, mostly non-significant pilot studies; a 2017 review called it scientifically unsupported.
| Marketed hero | INCI name | List position | What that suggests |
|---|---|---|---|
| Magnesium | Magnesium Sulfate | 16 of ~49 | Present, but below the base, fragrance, silicone and shea |
| Arnica | Arnica Montana Flower Extract | 20 of ~49 | Below magnesium and the preservative system |
| Hemp seed oil | Cannabis Sativa Seed Oil | 15 of ~49 | Just ahead of the magnesium it shares the label with |
For reference, if you want the mineral itself and nothing else, a bag of Epsom salt in a warm bath is the same compound as the “magnesium” in this lotion, for a fraction of the price — and it makes no claim about crossing your skin. If you specifically want a tallow-based balm that names magnesium sulfate on its own label, Evil Goods makes one: the Grass-Fed Tallow Magnesium Balm (that is ours). We would rather you know what any of them can and can’t do than pick by the front of the jar.
