Who Is Rosemary Waring?
Rosemary Waring, PhD is a biochemist and toxicologist who spent her career at the University of Birmingham in the United Kingdom. Her research focused on xenobiotic metabolism — how the body processes and detoxifies external compounds — with particular attention to sulfate metabolism and its clinical implications.
Within the magnesium and transdermal absorption world, Waring's research is significant because she designed and conducted one of the most methodologically credible studies of whether minerals can actually be absorbed through the skin during bathing — and she measured it directly.
The Bath Study — Key Findings
Waring's most frequently cited work involved a study in which participants soaked in baths of magnesium sulfate (Epsom salt) solution, and blood and urine levels of both magnesium and sulfate were measured before and after bathing, as well as at intervals following bathing.
What She Found:
-
Serum sulfate levels rose measurably in the majority of participants following bath soaking, consistent with transdermal absorption
-
Urine magnesium levels increased following bathing in most participants, suggesting elevated circulating magnesium
-
The increases were statistically significant and dose-responsive — higher concentration baths produced greater measured changes
-
Absorption appeared to increase with repeated soaking, suggesting a cumulative effect
-
Some variability between individuals was observed, suggesting that transdermal absorption rates differ between people
📚 Waring RH. Report on Absorption of Magnesium Sulfate (Epsom Salts) Across the Skin. University of Birmingham. 2004. School of Biosciences.
Why Waring's Research Is Considered More Rigorous
Compared to Shealy's clinical observations, Waring's study had several methodological advantages:
✓ Direct biological measurement: Rather than relying on self-reported symptoms or clinical impressions, Waring measured serum and urine levels — objective biochemical markers — before and after the intervention.
-
Standardized protocol: Bath concentration, temperature, duration, and timing of measurements were controlled
-
Multiple measurement points: Blood and urine were tested at several time intervals, capturing the absorption curve rather than just a single before/after snapshot
-
Dose-response relationship: The observation that higher concentrations produced greater measured changes is a hallmark of true physiological absorption rather than artifact
Limitations of Waring's Research
⚠️ Waring's study, while more rigorous than Shealy's observations, still has limitations the research community has noted.
-
Sample size was relatively small — the study involved 19 participants, limiting statistical power and generalizability
-
The study used magnesium sulfate (Epsom salt), not magnesium chloride — the form used in our products. Whether absorption rates and mechanisms are identical between these forms is not fully established
-
The study has not been independently replicated in peer-reviewed literature with larger sample sizes
-
Urine magnesium increase is an indirect measure of absorption — it reflects what the body is excreting, not necessarily what it has retained
-
The study did not measure intracellular or tissue magnesium levels, which many argue are the most clinically relevant measures
What Waring's Research Means for Transdermal Magnesium
Waring's work provides the strongest published evidence that minerals can be absorbed through the skin during immersion bathing. The dose-response relationship she observed is particularly significant — it suggests a real physiological mechanism rather than a measurement artifact.
The key question her research raises for the transdermal magnesium field is one of dose and consistency: how much is absorbed in a typical soak, how does this compare to oral supplementation, and does the absorption translate into meaningful tissue-level replenishment over time?
Waring's research doesn't prove that transdermal magnesium can fully replace oral supplementation for severely deficient individuals. What it does demonstrate is that the skin is not the impermeable barrier that critics sometimes suggest — minerals do cross it during immersion, and that crossing is measurable.
Connection to Our Products
Our Magnesium Soak uses Zechstein Inside® magnesium chloride brine — not magnesium sulfate (Epsom salt). The absorption mechanisms are similar (follicular and sweat gland pathways), but the compounds differ. Waring's research informs but does not directly validate our specific formulation.
What our formulation adds to Waring's research framework is an exceptionally pure starting material — a brine that has been independently safety-evaluated, batch-tested, and documented to contain negligible levels of heavy metals or contaminants. The purity of the source material matters for any transdermal application, because what goes into the bath can in principle cross the same pathways as the magnesium itself.
Our Certificate of Origin, Purity Statement, and Safety Evaluation are publicly available on our Purity & Sourcing page — download them anytime.
Frequently Asked Questions
Q: What did Rosemary Waring find about magnesium absorption?
A: Waring's University of Birmingham research found that bathing in magnesium sulfate (Epsom salt) solution produced measurable increases in serum sulfate and urinary magnesium in the majority of participants. The increases were dose-responsive — higher concentration baths produced greater changes — consistent with genuine transdermal absorption.
Q: Is Rosemary Waring's magnesium research peer-reviewed?
A: Waring's 2004 report was produced under the University of Birmingham School of Biosciences but was not published in a peer-reviewed journal in the traditional sense. It has been widely cited in the transdermal magnesium literature but has not been independently replicated in a larger peer-reviewed study — a legitimate limitation to note.
Q: Can magnesium be absorbed through the skin during a bath?
A: Waring's research, and subsequent work on transdermal drug and mineral delivery, suggests that yes, some degree of mineral absorption can occur through the skin during immersion bathing. The exact amount absorbed, and how this compares to oral supplementation, remains an area of ongoing research. The evidence is consistent with absorption occurring, even if the precise quantities are not fully established.
Q: What is the difference between Epsom salt and magnesium chloride?
A: Epsom salt is magnesium sulfate (MgSO4) — magnesium bound to sulfate. Magnesium chloride (MgCl2) is magnesium bound to chloride. Both can be used in bath soaks. Waring's research used magnesium sulfate. Our products use magnesium chloride from the Zechstein source. The absorption mechanisms are similar, but the compounds — and their additional mineral contributions — differ.
→ View our full sourcing documentation and Certificate of Origin on our Purity & Sourcing page.
→ Not sure where to start? Ask our free AI Magnesium Assistant — it's trained on Kristen's work and available anytime.
