Does soaking in Epsom salt actually deliver magnesium?

Epsom salt baths may not raise your magnesium meaningfully; the comfort people feel may come from the warm water.

Soaking in Epsom salt (magnesium sulfate) has not been shown to raise your magnesium in any meaningful way. Healthy skin is a tight barrier, and the studies behind the claim are small, unpublished or uncontrolled^1,2,3. The soothing effect people notice is likely the warm water, which helps sleep⁵. If you want more magnesium, oral intake is the route that has been tested^7,8.

What you can do

Enjoy the bath for its warmth: a warm bath or shower 1–2 hours before bed shortened time to fall asleep in trials that tested warm water, not Epsom salt⁵.
For more magnesium, an oral supplement has the modest trial evidence: it trimmed sleep onset by about 17 minutes in older adults but did not clearly prevent cramps^7,8.
For dry, eczema-prone skin, a short soak in magnesium-rich Dead Sea salt improved hydration in a small trial; Epsom salt itself is untested for skin⁴.

Be careful if

Never swallow Epsom salt as a home laxative: it has caused severe magnesium toxicity needing dialysis⁶.
If you have kidney disease, ask a clinician before using any magnesium product: a review links toxic magnesium levels mainly to severe kidney insufficiency¹.
Keep baths comfortably warm and short: bath heat illness is documented, numb diabetic feet have been burned in foot soaks, and early-pregnancy overheating is linked to neural tube defects^9,10,12.

Go deeper

How it works What it does in your body, in plain words 2 min

The claim

Epsom salt is magnesium sulfate. Marketing says the magnesium passes through your skin and replenishes your cells better than a tablet¹.

Why it is doubtful

The outer skin layer is built to keep substances out. A mineral must cross it or enter through sweat glands and hair follicles, which cover only about 0.1% to 1% of the skin¹. A 2017 review concluded that the claim is scientifically unsupported. A study it cites in eight volunteers found no change in blood magnesium after two hours in 35°C spa water, and a placebo-controlled trial of a magnesium sulfate lotion in 34 volunteers found no difference in blood magnesium¹.

The studies that say yes

An often-quoted 19-person experiment, reported only on an Epsom salt industry website, found rising blood magnesium after daily baths; the review judged such studies to be of questionable quality¹. In a 25-person pilot, a magnesium cream raised serum magnesium from 0.82 to 0.89 mmol/L against 0.77 to 0.79 with placebo, but the rise in the magnesium group was not significant overall (p=0.29) and only reached significance in a subgroup of non-athletes². In 40 women with fibromyalgia, a magnesium chloride spray was followed by better questionnaire scores, but there was no control group³. A 2025 trial of Epsom salt foot baths in 104 cancer patients reported delayed and milder chemotherapy-related nerve symptoms compared with standard care alone, with no placebo bath described, so it cannot show that the salt mattered¹¹.

What a bath does offer

Warm water has its own benefits. A warm bath or shower 1 to 2 hours before bed shortened the time to fall asleep in a meta-analysis of 17 studies⁵. In a small forearm trial, a 15-minute soak in magnesium-rich Dead Sea salt improved skin barrier function and hydration compared with tap water; that salt is magnesium chloride, not Epsom salt, and it measured skin, not blood magnesium⁴. See hydrotherapy and hot baths.

If you want magnesium

A Cochrane review of 11 trials (735 people) found that oral magnesium is unlikely to prevent cramps in older adults⁷. Three small trials in 151 older adults suggested oral magnesium shortened sleep onset by 17 minutes, but the evidence was low to very low quality⁸. See why magnesium matters.

Safety

Swallowing Epsom salt has caused dangerous magnesium levels⁶. A review calls severe toxicity very rare, seen mainly in severe kidney insufficiency or after medical treatment¹. Hot water carries its own risks: heat illness, and burns in people who cannot feel heat in their feet^9,12.

The evidence The studies, what they found, and how much to trust them 4 min · 12 sources

What the review found

Gröber and colleagues examined the evidence for transdermal magnesium and concluded that the propagation of transdermal magnesium is scientifically unsupported. They note that absorption, if any, would have to go through hair follicles and sweat glands, that a recent laboratory study showed magnesium ions can penetrate the stratum corneum with hair follicle help but did not report how much, and that the clinical relevance of any such amount is unknown. They cite a placebo-controlled phase I study in 34 healthy volunteers who applied 10 mL of a magnesium sulfate lotion three times daily for three days, with no significant difference in blood magnesium from placebo, and an eight-person, two-hour immersion in spa water at 35°C with no change in plasma magnesium, calcium or phosphate. In a cadaver skin diffusion study they describe, magnesium chloride solution crossed the skin about as little as a phosphate buffer control (6.18 and 5.62 micrograms at 24 hours), while creams delivered about 25 to 30 micrograms. The review also describes a hair-analysis study in 9 people and an Epsom salt bath study in 19 people (12-minute daily baths for seven days) that reported blood magnesium rising from a mean of about 105 to 141 ppm; it called such studies questionable and noted the bath study was never peer reviewed¹.

Small trials of creams, sprays and foot baths

Kass and colleagues randomized 25 people, single-blind, to a cream supplying 56 mg of magnesium a day or placebo for two weeks. Serum magnesium rose from 0.82 to 0.89 mmol/L in the magnesium group and from 0.77 to 0.79 in the placebo group (p=0.29), reaching significance (p=0.02) only in non-athletes; urinary excretion did not change significantly (p=0.48). The authors called for higher doses and longer trials². Engen and colleagues enrolled 40 women with fibromyalgia, of whom 24 finished four weeks of a magnesium chloride spray twice daily; the Revised Fibromyalgia Impact Questionnaire improved (total score P=0.001), but with no control group this shows feasibility, not efficacy³. Proksch and colleagues had volunteers with atopic dry skin soak one forearm for 15 minutes in a 5% Dead Sea salt solution and the other in tap water; barrier function improved in the subgroup with elevated water loss, and hydration improved, while roughness and redness fell. The authors attributed this to the high magnesium content, which was not tested⁴. Ankar and colleagues randomized 104 cancer patients, split into asymptomatic and symptomatic groups, to standard hospital care with or without Epsom salt foot baths. Deterioration of neuropathy grade in asymptomatic patients was 42.31% with foot baths versus 96.15% without (P<0.05), and symptomatic patients improved more. The abstract describes no placebo bath or blinding, and the trial did not measure magnesium levels, so warmth, attention or expectation could explain the result¹¹.

Warm water and oral magnesium

Haghayegh and colleagues included 17 studies, 13 with comparable data: passive heating at 40 to 42.5°C improved sleep quality and efficiency, and 1 to 2 hours before bed it shortened sleep onset even at 10 minutes⁵. For oral magnesium, the cramps review of 11 trials (735 people) found no significant difference from placebo in cramps per week (mean difference -0.18; 95% CI -0.84 to 0.49; 307 people) in idiopathic cramps, with more gastrointestinal side effects such as diarrhea⁷. The insomnia meta-analysis of three trials (151 older adults) found sleep onset 17.36 minutes shorter (95% CI 7.44 to 27.27), with total sleep time unchanged and all trials at moderate-to-high risk of bias⁸.

Safety data

A 56-year-old man who swallowed Epsom salt as a laxative arrived weak, with a slow heartbeat and low blood pressure, then developed altered mental status and respiratory depression; his magnesium was above 3.91 mmol/L and fell rapidly once dialysis started⁶. The review notes that severe hypermagnesemia is very rare and is seen in severe renal insufficiency or after medical treatment¹. In 4,593 Japanese bath-related emergencies, 30% of survivors had body temperatures above 38°C, suggesting heat illness in hot water⁹. In a French series of 30 diabetic inpatients with deep leg burns, 60% had neuropathy and 54% of the burns happened during a footbath¹². Chambers concluded that hot tub or spa use in early pregnancy could raise core temperature to risky levels, with limited human data linking it to neural tube defects¹⁰.

Where the evidence conflicts

The positive absorption claims come from unpublished or uncontrolled work, and the controlled work is negative or inconclusive^1,2,3. Yet bath trials for sleep and symptoms do show benefit from warm water, so people can truthfully feel better without absorbing magnesium^5,11. A controlled trial of baths with measured blood and urine magnesium would settle the question, and we found none.

Bottom line

Confidence is low (2 of 5). The best-controlled evidence shows little or no rise in blood magnesium from bathing or magnesium lotions, and the supportive evidence is weak^1,2. Warm water probably explains the comfort⁵. Oral intake has the most testing, with modest results^7,8. Do not swallow bath salts⁶.

Sources

Myth or Reality-Transdermal Magnesium?. Gröber U, Werner T, Vormann J, et al.. Nutrients, 2017. PubMed 28788060
Effect of transdermal magnesium cream on serum and urinary magnesium levels in humans: A pilot study. Kass L, Rosanoff A, Tanner A, et al.. PLoS One, 2017. PubMed 28403154
Effects of transdermal magnesium chloride on quality of life for patients with fibromyalgia: a feasibility study. Engen DJ, McAllister SJ, Whipple MO, et al.. J Integr Med, 2015. PubMed 26343101
Bathing in a magnesium-rich Dead Sea salt solution improves skin barrier function, enhances skin hydration, and reduces inflammation in atopic dry skin. Proksch E, Nissen HP, Bremgartner M, et al.. Int J Dermatol, 2005. PubMed 15689218
Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis. Haghayegh S, Khoshnevis S, Smolensky MH, et al.. Sleep Med Rev, 2019. PubMed 31102877
Epsom Salt Ingestion Leading to Severe Hypermagnesemia Necessitating Dialysis. Walker P, Parnell S, Dillon RC. J Emerg Med, 2020. PubMed 32389435
Magnesium for skeletal muscle cramps. Garrison SR, Korownyk CS, Kolber MR, et al.. Cochrane Database Syst Rev, 2020. PubMed 32956536
Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis. Mah J, Pitre T. BMC Complement Med Ther, 2021. PubMed 33865376
Incidence and Characteristics of Bath-related Accidents. Suzuki M, Shimbo T, Ikaga T, et al.. Intern Med, 2019. PubMed 30146565
Risks of hyperthermia associated with hot tub or spa use by pregnant women. Chambers CD. Birth Defects Res A Clin Mol Teratol, 2006. PubMed 16998815
Assess the Efficacy of Epsom Salt Foot Bath in Preventing or Delaying the Onset of Chemotherapy-induced Neurological Manifestations in Cancer Patients. Ankar R, Singh S, Wanjari M, et al.. J Pharm Bioallied Sci, 2025. PubMed 40510964
Brûlures Profondes Des Membres Inférieurs Chez Les Patients Diabétiques: À Propos De 30 Cas. Privé S, Benyamina M, Mimoun M, et al.. Ann Burns Fire Disasters, 2022. PubMed 37016598