Slather, Soak, or Swallow? What the Science Really Says About Magnesium Absorption
Sprays, Epsom salts, and lotions: do they actually work — and how do they stack up against oral supplementation?
Magnesium: Myth, Mineral, or Marketing?
What the Science Really Says About Topical Magnesium
Raise your hand if you've ever stood in the supplement aisle, staring at a magnesium spray that promised to be “faster-absorbing,” “more bioavailable,” and essentially a one-way ticket to stress-free muscle bliss — all via your skin. 🙋
You are not alone. Topical magnesium — including sprays, Epsom salt baths, and lotions — has exploded in popularity. The wellness world loves it. Instagram loves it. Your neighbor who swears by it loves it.
But what does the research actually say? Is topical magnesium a legitimate strategy to boost your levels, or are we essentially rubbing expensive salt water on ourselves and calling it self-care?
Good news: we’re going to sort through all of it. Let’s start with the basics before we get to the good stuff.
Why Magnesium Matters (A Lot)
Before we debate how magnesium gets into your body, let’s briefly appreciate why it matters in the first place.
Magnesium is involved in over 300 enzymatic reactions in the body — and some estimates put that number even higher, up to 600. It plays critical roles in energy metabolism (ATP production), protein synthesis, muscle and nerve function, blood pressure regulation, blood glucose control, and bone development (1 ). In other words, magnesium is not a niche nutrient. It’s essential infrastructure.
And here’s the kicker: magnesium inadequacy is genuinely common. Estimates suggest that roughly 48% of U.S. adults fail to consume the recommended amount of magnesium from food, and globally, an estimated 2.4 billion people — around 31% of the world’s population — do not meet recommended intake levels (2,3). Processed food diets, depleted soil, and the decline of whole grain and vegetable consumption are all contributing factors.
The RDA for magnesium is approximately 420 mg/day for adult men and 320 mg/day for adult women — levels many of us are quietly not hitting (3)
So yes, magnesium status matters. The question is simply: does rubbing it on your skin help?
How Skin Actually Works (Spoiler: It’s a Barrier, Not a Door)
Here’s the fundamental challenge with topical magnesium: your skin’s job is to keep stuff out, not let stuff in.
The outermost layer of the skin — the stratum corneum — is specifically designed to act as a barrier against external chemicals, allergens, UV radiation, microorganisms, and moisture loss. It’s quite good at this job (4).
For a substance to be absorbed through the skin and enter the bloodstream, it typically needs to either penetrate the stratum corneum directly (difficult for charged mineral ions like magnesium) or pass through the skin appendages: hair follicles and sweat glands (4). The catch? Hair follicles and sweat glands together make up only about 0.1% to 1% of total skin surface area (4). That is a very small doorway.
Research has confirmed that magnesium ions can penetrate the stratum corneum — and that hair follicles significantly facilitate this process, potentially contributing up to 40% of absorption. Permeation also appears to increase with higher concentrations of magnesium and longer skin contact time (4). So the pathway exists. The questions are: how much gets through, and does it matter clinically?
The skin is designed to be a barrier — not a portal. That doesn’t mean topical magnesium does nothing, but it does mean we need to look honestly at the evidence before claiming it’s superior to the tried-and-true oral route.
What the Research Actually Says
Magnesium Sprays and Lotions
Let’s start with the most popular format: topical sprays and creams containing magnesium chloride.
A 2017 pilot study (Kass et al., published in PLOS ONE) is one of the most-cited human studies on this topic. Twenty-five participants were randomly assigned to apply either a 56 mg/day magnesium cream or a placebo cream for two weeks. After the intervention, the magnesium group showed a clinically relevant increase in serum magnesium (from 0.82 to 0.89 mmol/L), while the placebo group showed virtually no change. However — and this is important — this difference only reached statistical significance in a subgroup of non-athletes (n=20), not in the full sample (5). That means we’re looking at a small pilot study with mixed results. Interesting? Yes. Definitive? Not quite.
A comprehensive 2017 review in the journal Nutrients (Gröber et al.) evaluated the existing literature on transdermal magnesium and concluded bluntly that “the propagation of transdermal magnesium is scientifically unsupported.” The authors noted that the available evidence relies heavily on small, low-quality studies, and that the skin’s barrier function makes meaningful systemic absorption fundamentally uncertain (4).
A 2025 review in the Journal of the American Academy of Dermatology Reviews noted that while topical magnesium formulations show promise for specific dermatological applications (like atopic dermatitis and wound healing), “further pharmacokinetic studies are warranted to characterize transdermal absorption, bioavailability, and interactions with calcium-dependent epidermal processes” (6). Translation: there may be localized skin benefits, but the systemic absorption story is still being written.
A Special Case: Topical Magnesium in Patients Who Cannot Absorb It Orally
Here's where the story takes a genuinely interesting turn.
Most of us absorb magnesium the old-fashioned way — we eat it or swallow a supplement, and our small intestine does the work. But what about people whose small intestine has been surgically removed or bypassed? For them, that route simply isn't available.
A 2024 pilot study published in the peer-reviewed journal Intestinal Failure (Nightingale, Al Bakir, & Adaba) looked at exactly this situation. The participants all had an ileostomy — a surgical opening in the abdomen that reroutes digestion after part of the bowel has been removed — and were dealing with persistently low magnesium levels that oral supplements couldn't fix. Their bodies had lost the plumbing needed to absorb magnesium through the gut.
Six patients applied a magnesium chloride spray to their torso and arms twice a day for six weeks, delivering 150 mg of magnesium daily. The results were encouraging: three patients showed a measurable rise in their blood magnesium levels, and one was able to cancel a scheduled magnesium IV infusion entirely. The other three held steady — their levels didn't rise, but they didn't fall either. Perhaps most meaningfully for quality of life, muscle cramps — a hallmark and deeply uncomfortable symptom of magnesium deficiency — improved in five of the six patients (11).
This is currently the strongest peer-reviewed human evidence that a magnesium spray can raise blood magnesium levels in people who are genuinely deficient. It matters because it shows the skin route can step in when the gut route is off the table. The authors concluded that topical magnesium spray is worth considering for this population before moving to IV magnesium — which is a much bigger undertaking.
A few important caveats, though. This was only six people — a very small group, which means the findings are promising but not yet definitive. And this population is highly specific: their digestive systems work differently from those of healthy adults, which is actually part of why the study is informative. When the gut is out of the picture, the skin's contribution becomes easier to measure. That doesn't mean the same thing happens in someone with fully intact digestion.
It's also worth noting that the magnesium spray and the laboratory testing were funded by BetterYou™, the company that makes the product used in the study. The researchers state they maintained independent control over the study design and findings, which is standard practice — but it's a disclosure worth knowing about.
The takeaway: if you or someone you know has had bowel surgery and struggles with chronically low magnesium, topical magnesium is a legitimate option now backed by peer-reviewed research — and absolutely worth a conversation with your gastroenterologist or dietitian. For everyone else with an intact digestive system, the evidence base for topical magnesium remains much thinner than the marketing suggests.
Epsom Salt Baths (Magnesium Sulfate)
Ah, the beloved Epsom salt bath. A sore-muscle staple, a relaxation ritual, and a topic of genuinely contested science.
The most frequently cited human bathing study was conducted by Waring at the University of Birmingham. Nineteen subjects soaked in hot Epsom salt baths (temperatures of 50–55°C) for 12 minutes daily for 7 consecutive days. Of the 19 subjects, 16 showed a rise in plasma magnesium levels — from a pre-bath mean of 104.68 ppm/mL to 140.98 ppm/mL after seven days. Urinary magnesium also increased, suggesting the mineral crossed the skin barrier (7).
This sounds pretty compelling! Until you look more carefully: this study has no control group and was never published in a peer-reviewed journal. That alone is a significant limitation when drawing clinical conclusions (4).
It’s also worth noting that magnesium sulfate (Epsom salt) is considered one of the less bioavailable forms of magnesium — even when taken orally. The National Institutes of Health (NIH) Office of Dietary Supplements notes that magnesium in the aspartate, citrate, lactate, and chloride forms tends to have higher bioavailability than magnesium oxide and magnesium sulfate (8).
The bottom line on Epsom salts: some magnesium may cross the skin, particularly with prolonged hot soaks and higher concentrations. But we don’t have strong, peer-reviewed evidence establishing how much, whether it’s clinically meaningful, or whether it’s reliable enough to use as a therapeutic strategy for deficiency.
So How Does Topical Compare to Oral Magnesium?
This is the money question — because wellness marketing loves to claim that topical magnesium “bypasses the digestive system” for “nearly 100% absorption,” often implying oral supplements are inferior. Let’s fact-check that.
Oral magnesium is absorbed primarily in the small intestine (distal jejunum and ileum), with some additional absorption in the colon. The overall absorption rate from food and supplements is typically estimated at 30–50%, though this varies considerably based on magnesium status (deficient individuals absorb more), the form of magnesium, and other dietary factors (8,9).
Importantly, not all oral magnesium is created equal. Organic forms — magnesium citrate, glycinate, malate, and lactate — are generally better absorbed than inorganic forms like magnesium oxide and sulfate. A systematic review in Nutrition (Pardo et al., 2021) confirmed that organic magnesium salts tend to have higher bioavailability and better gastrointestinal tolerability than inorganic forms (10).
In contrast, the evidence for topical magnesium absorption is far less established in healthy populations. The most convincing human data — the 2024 Nightingale et al. pilot study — was conducted specifically in ileostomy patients for whom oral absorption was already failing. A well-controlled, adequately powered trial demonstrating consistent serum magnesium increases from topical products in healthy adults does not yet exist.
The Gröber 2017 review directly addressed the marketing claim of “near-100% absorption” for topical magnesium, noting that no study has demonstrated this — and that the physiological limitations of the skin make such claims implausible (4).
A fair summary of the evidence: Oral magnesium, particularly in well-absorbed organic forms, has robust evidence for raising magnesium status. Topical magnesium has some preliminary, small-scale evidence suggesting possible absorption — but claims of superiority to oral supplementation are not currently supported by science.
If you have a genuine magnesium deficiency, oral supplementation in an organic form — not a spray — remains the evidence-based gold standard.
To learn more about magnesium supplements, check out my other article: “Tired, Wired, & Stressed? Let’s Talk About Magnesium.”
But Wait — Are There Any Real Benefits to Topical Magnesium?
Here’s where I want to add some nuance, because this isn’t a story of pure debunking. There are a few legitimate considerations:
Skin-level benefits may be real. The 2025 JAAD Reviews paper noted that topical magnesium formulations have shown evidence of benefit in dermatological contexts — specifically in atopic dermatitis, diaper dermatitis, wound healing, and photoprotection. These are local effects on skin barrier function and inflammation rather than systemic mineral repletion (6).
The relaxation effect is real — but the mechanism is uncertain. A warm Epsom salt bath is genuinely relaxing. Whether that’s primarily because of magnesium absorption, the warmth of the water, or simply the restorative act of lying still for 20 minutes is difficult to disentangle.
It may complement oral supplementation. For individuals who experience GI side effects (like loose stools) from oral magnesium — a common and very real issue, especially at higher doses — topical products may offer a lower-dose adjunct. Just don’t count on them to carry the load alone.
Skin irritation is possible. It’s worth noting that magnesium sprays can cause tingling, itching, or burning on the skin, particularly with concentrated formulations on sensitive or freshly shaved skin. Start slowly and patch-test first.
The Bottom Line (Without the Hype)
Topical magnesium — sprays, lotions, and Epsom salt soaks — is not snake oil. Some magnesium does appear to cross the skin, particularly through hair follicles and with longer exposure. There may be genuine localized skin benefits.
But the marketing claims have gotten way ahead of the science. Topical magnesium is not “superior” to oral supplementation. It is not a reliable strategy for correcting a clinical magnesium deficiency. And the claim of “near-100% absorption” has no peer-reviewed evidence behind it.
If your goal is to support your magnesium status:
Prioritize magnesium-rich foods: leafy greens, legumes, nuts, seeds, whole grains, and dark chocolate (yes, really).
If supplementing, choose well-absorbed oral forms: magnesium citrate, glycinate, or malate tend to be better tolerated and more bioavailable than oxide or sulfate.8,10
If you enjoy Epsom salt baths or magnesium lotions, go for it — just don’t count on them as your primary magnesium strategy.
If you’re considering supplementation due to suspected deficiency, talk with a registered dietitian nutritionist or your healthcare provider. Magnesium status is notoriously difficult to assess with standard serum testing, and individual needs vary considerably.
References
1. Al Alawi, A.M., Majoni, S.W., & Falhammar, H. (2018). Magnesium and Human Health: Perspectives and Research Directions. International Journal of Endocrinology, 2018, 9041694. https://doi.org/10.1155/2018/9041694
2. Rosanoff, A., Weaver, C.M., & Rude, R.K. (2012). Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews, 70(3), 153–164. https://doi.org/10.1111/j.1753-4887.2011.00465.x
3. Tarleton, E.K., Kennedy, A.G., Rose, G.L., et al. (2025/2024 review). Global Dietary Magnesium Deficiency: Prevalence, Underlying Causes, Health Consequences, and Strategic Solutions. International Journal of Vitamins and Nutrition Research, 95(6). https://doi.org/10.31083/IJVNR46828
4. Gröber, U., Werner, T., Vormann, J., & Kisters, K. (2017). Myth or Reality—Transdermal Magnesium? Nutrients, 9(8), 813. https://doi.org/10.3390/nu9080813 . PMC5579607
5. Kass, L.S., Skinner, P., & Plesset, M. (2017). Effect of transdermal magnesium cream on serum and urinary magnesium levels in humans: A pilot study. PLOS ONE, 12(4), e0174817. https://doi.org/10.1371/journal.pone.0174817 . PMC5389641
6. Chalupczak, N.V. & Lipner, S.R. (2026) The role of magnesium in dermatology. JAAD Reviews, 7, 24-30. https://doi.org/10.1016/j.jdrv.2025.10.004
7. Waring, R.H. (2006). Report on Absorption of magnesium sulfate (Epsom salts) across the skin. University of Birmingham, School of Biosciences. https://www.epsomsaltcouncil.org/wp-content/uploads/2015/10/report_on_absorption_of_magnesium_sulfate.pdf [Non-peer-reviewed report; referenced here for context only, with noted methodological limitations]
8. National Institutes of Health, Office of Dietary Supplements. (2024). Magnesium Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
9. Blancquaert, L., Vervaet, C., & Derave, W. (2019). Predicting and Testing Bioavailability of Magnesium Supplements. Nutrients, 11(7), 1663. https://doi.org/10.3390/nu11071663
10. Pardo, M.R., Garicano Vilar, E., San Mauro Martín, I., & Camina Martín, M.A. (2021). Bioavailability of magnesium food supplements: A systematic review. Nutrition, 89, 111294. https://doi.org/10.1016/j.nut.2021.111294
11. Nightingale, J., Al Bakir, I., & Adaba, F. (2024). Pilot study of a topical magnesium preparation to treat hypomagnesaemia in patients with an ileostomy. Intestinal Failure (New York, N.Y.), 2, 100018. https://doi.org/10.1016/j.intf.2024.100018
