Magnesium spray: absorption through the skin is not adequately proven

A magnesium spray is easy to apply. Whether a reliably usable amount of magnesium actually gets into the body is a different question. The human study reviewed here is not enough to classify a spray as an equivalent substitute for a justified oral treatment or as a reliable therapy for deficiency.

What the frequently cited pilot trial actually measured

In 2017, 25 people were assigned to a magnesium cream or a placebo cream. Over two weeks, the researchers looked at magnesium in the serum and its excretion in urine. Across the whole group, the changes with the magnesium cream were not statistically significant. A significant rise in serum levels appeared only in a subgroup that excluded the athletically active participants. [1]

The finding in this subgroup could be checked in a larger study. Whether all users absorb enough magnesium remains an open question. In addition, the study tested a cream, not just any spray. One author disclosed a possible future financial interest in a different magnesium cream. [1]

Three claims need three different kinds of evidence

“Magnesium gets through the skin” describes, first of all, transport. “The product corrects a deficiency” requires clinically appropriate evidence of efficacy. “This makes cramps or sleep problems go away” goes one step further and requires studies of those complaints.

Each of these steps would need its own data. Even when a lab value rises measurably, a particular symptom can stay the same. Advertising often squeezes these questions into a single sentence, even though the necessary evidence is missing.

Why tingling is not an absorption test

The subjective feeling after applying it says nothing about how much was absorbed. A pleasant massage effect cannot show what share of the effect is due to magnesium either. A meaningful product comparison would need to pin down, among other things, the formulation, the amount applied, the comparison treatment and the measurement method.

“Magnesium oil” is also, first of all, a product name. Whether magnesium is absorbed, how much, and what clinical benefit that has would have to be studied for the specific product.

When oral products are poorly tolerated

In that case, the questions to settle are whether a supplement is needed and which treatment fits the reason for taking it. Switching to skin application assumes the product is suitable for that purpose; poor tolerance of a capsule does not answer this question by itself. The basics article separates diet, lab findings and the reason for treatment; the comparison of forms explains why absorption and effect are different measures.

A cosmetic use or personal preference may call for a different judgment than treating a deficiency. The claim that a spray reliably covers your magnesium needs requires stronger data than the small pilot trial. This limit holds even when many personal accounts describe an improvement: without a comparison, effect, expectation and natural course cannot be cleanly separated.

Source

1. Kass et al., 2017: transdermal magnesium cream: randomized pilot study; abstract, subgroup finding and conflict of interest reviewed. Not solid evidence of efficacy for sprays in general.