Magnesium spray benefits: what the evidence says about absorption, sleep and cramps

Magnesium spray, sold as “magnesium oil”, is magnesium chloride dissolved in water near saturation; there is no oil in it. You rub it into your skin, and the bottle says the magnesium goes where your diet did not. That last step is what this page checks, with arithmetic for the part that lands on you and the studies for the part that gets through. If you have already decided to try one, our magnesium spray buying guide compares the bottles on what you can check. This page sits in our recovery tools section.

Does magnesium spray work? Is it absorbed through skin?

Skin is built to keep things out. Its outer layer, the stratum corneum, is 15 to 20 layers of dead cells in a fatty matrix, and what crosses it in quantity is mostly fat-soluble. Magnesium in a chloride solution is a charged, water-bound ion, the opposite of that.

The 2017 review by Gröber, Werner, Vormann and Kisters in Nutrients, titled “Myth or Reality—Transdermal Magnesium?”, sets out the problem. The only plausible routes are hair follicles and sweat glands, which the authors put at 0.1 to 1% of the skin’s surface. A 2016 lab study they cite found magnesium does permeate skin, helped by follicles, but did not report how much. Their conclusion is blunt: “we cannot yet recommend the application of transdermal magnesium.”

The human studies the marketing leans on are thin:

• Watkins and Josling, 2010. Nine people, no control group, 12 weeks of 20 sprays a day plus a twice-weekly foot soak. The outcome was magnesium in hair samples, which the review notes is a poor marker of body magnesium, and no blood magnesium was reported.
• Waring’s Epsom salt bath study. Nineteen people, seven daily baths, rises in blood and urine magnesium reported, but published only on the Epsom Salt Council’s website, never in a peer-reviewed journal.
• Kass and colleagues, PLOS ONE, 2017. The best of them: a single-blind randomized pilot in which 25 people used either a magnesium cream (56 mg of magnesium a day) or a placebo cream for two weeks. Serum magnesium rose from 0.82 to 0.89 mmol/L in the magnesium group, which was not statistically significant (p = 0.29). Urinary magnesium did not change significantly either (p = 0.48). Only a subgroup of 20 non-athletes reached significance for serum. One author disclosed a future royalty interest in a different magnesium cream.

Since 2017 the newer human studies have been uncontrolled pilots in sick patients, such as a 2023 single-arm study of a magnesium chloride spray in 20 people with advanced kidney disease (14 finished) and a 2024 ileostomy study in which two of six finishers saw serum magnesium rise. With no placebo group, neither can say what the spray did.

Even a good trial would struggle. An adult body holds about 25 grams of magnesium, and less than 1% of it is in blood serum, which the kidneys hold within a narrow range, according to the NIH Office of Dietary Supplements. A small extra input would barely move a serum test, which is why the honest summary is “not shown”, not “shown not to work”.

How much magnesium a spray puts on your skin

This part needs no trial. The labels state it, and the arithmetic is the label figure times the number of sprays.

Every figure is the manufacturer’s or the listing’s, read on 15 October 2026. The Ancient Minerals per-spray figures are our division of their per-millilitre figure; the ASUTRA row borrows the other labels’ range because its listing gives none.

Now set that against what the body uses. The adult Recommended Dietary Allowance is 400 to 420 mg a day for men and 310 to 320 mg for women, from all sources. The Tolerable Upper Intake Level is 350 mg a day, and it applies only to magnesium from supplements and medicines taken by mouth; it does not cover food, and it was not written with skin in mind. For scale, an ounce of dry-roasted almonds carries about 80 mg. All three figures are from the NIH Office of Dietary Supplements.

So a heavy user following ASUTRA’s 30-spray directions may put more magnesium on their skin than the RDA. That is what lands on you, not what is absorbed, and almost no marketing separates the two. The Kass trial applied 56 mg a day and could not show a significant rise, and if follicles and sweat glands are the only way in, a bigger dose on the skin need not mean much more in the blood. Nobody has measured the absorbed fraction from a spray in people, so any milligram figure for absorption is a guess.

Magnesium spray for sleep

We found no trial of a magnesium spray, oil or lotion for sleep; a search of Europe PMC titles and abstracts turned up nothing designed around it. The evidence people borrow is for oral magnesium. A 2021 systematic review and meta-analysis by Mah and Pitre in BMC Complementary Medicine and Therapies found three randomized trials comparing oral magnesium with placebo in 151 older adults. Pooled, people fell asleep about 17 minutes sooner on magnesium. Total sleep time was not significantly different. The authors rated all three trials at moderate to high risk of bias and the evidence low to very low quality. That is a weak result for magnesium that definitely reached the bloodstream; a spray inherits none of it until absorption is shown.

What is left is the routine: a minute rubbing your calves before bed may help you wind down, and that is not evidence about magnesium. Our page on whether mouth taping works grades another popular sleep fix the same way.

Magnesium spray for leg cramps

The 2020 Cochrane review by Garrison and colleagues pooled 11 randomized trials with 735 participants. All but one gave magnesium by mouth (100 to 520 mg of elemental magnesium a day); one used intravenous infusions. For idiopathic cramps, the ordinary unexplained night cramps of older adults, magnesium did not reduce cramp frequency, intensity or duration compared with placebo, and the authors concluded it is unlikely to help. For pregnancy-associated cramps the evidence was conflicting and very low certainty. Evidence for exercise-related cramps was not reliable enough to judge.

No controlled trial has tested a spray for cramps. The logic runs one way: if magnesium delivered by mouth or by vein does not prevent ordinary cramps, magnesium that may not cross the skin has a harder case to make, not an easier one.

Magnesium spray for pain

The study most often cited is a 2015 feasibility study from the Mayo Clinic (Engen and colleagues, Journal of Integrative Medicine). Forty women with fibromyalgia sprayed a magnesium chloride solution on their arms and legs, four sprays per limb twice a day, 32 sprays daily, for four weeks. Twenty-four finished. Scores on a fibromyalgia questionnaire improved significantly from baseline.

It had no control group and no blinding; the trial registration lists it as single-group and open-label. Questionnaire scores move with attention, expectation and time, which is what a placebo arm exists to subtract. The 2023 kidney-disease neuropathy study had the same design. Both are reasons to run a proper trial, not evidence that the spray relieves pain. For sore muscles after training, we grade the evidence for the massage gun and the TENS unit the same way.

Magnesium spray on feet

Feet are the most common place people are told to spray, sometimes with the claim that feet “absorb better”. The anatomy points the other way. The soles have the thickest stratum corneum on the body and no hair follicles at all, and follicles are the route the one lab permeation study found magnesium using. Soles do have dense sweat glands, the other candidate route, but no study has measured magnesium uptake through the sole of the foot.

There are practical reasons to use feet anyway: the sting is milder on thick skin, the residue goes under a sock, and night cramps tend to be in the calf and foot. Those are comfort reasons, not absorption reasons. If you like a foot routine, a foot massager is the part with a mechanism you can feel.

Magnesium spray side effects

The side effects are almost all on the skin:

• Stinging, itching and redness. Ancient Minerals attributes the tingling to “the high concentration of magnesium chloride” and suggests diluting 1:1 with water. Some listings instead call the tingle a sign of magnesium deficiency. There is no evidence for that; a sensation salt water also produces on a scratch is not a diagnostic test.
• Salt residue and stickiness. It dries to a film of salt. Several brands suggest wiping or rinsing it off after about 20 minutes.
• Broken or freshly shaved skin. Expect more sting; labels say to keep it off open skin and out of the eyes.

Magnesium toxicity, which can cause low blood pressure and an irregular heartbeat, is documented for laxatives and antacids at doses typically above 5,000 mg a day, per the NIH fact sheet. Nobody has shown a spray delivering enough to matter, which is reassuring for most people and not the same as safe for everyone.

The benefits of magnesium oil spray we can stand behind

Strip out what has not been shown and three things remain. It is cheap and, for most skin, low-risk. It does not go through the gut, so it avoids the diarrhea oral magnesium chloride and oxide are known for, per the NIH, though partly because little of it may be absorbed at all. And it comes with a minute of massage. That is a short list, and we would rather give you it than the long one on the bottle. If you want to try it on those terms, buy the plainest bottle with a stated dose.

Our buying guide compares it with four other bottles.

What we have not measured

We have not tested any magnesium spray. Every milligram-per-spray figure on this page is manufacturer- or listing-stated, and the per-day figures are our multiplication of them by the label directions. Study results are as the authors reported them: we read the Kass trial and the 2017 review in full, the Cochrane review, the sleep meta-analysis and the newer pilots as abstracts and published summaries, and the Watkins and Waring studies only as the 2017 review describes them.

The dose figures can be checked on a bench, and we owe that check: weigh 50 sprays from each bottle on a 0.01 g scale to get millilitres per spray, then titrate a diluted sample with a water-hardness EDTA kit to get milligrams of magnesium per millilitre, and compare the product with the label. That is n=1 bottle per brand, and spray volume varies with pump pressure, so we would report the spread across the 50 sprays, not one number.

The question that matters most, how much crosses the skin, cannot be answered on a bench. It needs blood and 24-hour urine samples, ideally isotope-labelled magnesium, a placebo arm and an ethics board, and we will not pretend a home test could stand in for it. Our how we test page says the same about every figure on the site.