But she says those with already ample or high levels of magnesium will see little benefit from supplementation. “The body will just excrete it.”

Oral v topical application

While those touting the benefits of the spray claim that topical application allows for greater and more rapid absorption than oral alternatives, Kendall says there is no scientific evidence for this.

She stipulates that more studies, with greater sample sizes, need to be done, but says at this stage oral supplementation has been shown to be more effective.

Kendall explains magnesium would have to travel a long way through the skin barrier to be effective. “Magnesium has to penetrate the skin and then has to either go into a hair follicle or sweat gland. And then from there, it has to get into the bloodstream. But this can be quite difficult based on the size of the magnesium molecules, but also the properties of magnesium itself.”

She adds dermal application of magnesium via a spray or cream will effectively dilute its concentration, and thus reduce its strength.

Kendall says anecdotal claims about the effectiveness of magnesium spray for things like sleep and muscle recovery are likely due to the placebo effect.

She adds it can be difficult to accurately judge the effectiveness of aids for sleep and recovery. “Recovery specifically is a very perceived feeling or effect, so it’s difficult to objectively measure the impact of a supplement.”

“[But] I believe some people will use these recovery methods and say they work, to which I say ‘That’s great. If it works for you, then keep doing it’.”

Magnesium spray for kids

Many proponents of magnesium spray promote it as a sleep aid for children. But Michael Gradisar, head of sleep science at Sleep Cycle, sees little need for magnesium supplementation in kids. He says it’s uncommon for children to be deficient in magnesium, as they can get more than enough from a well-rounded diet.

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“To say that potentially magnesium could be a solution for kids flies in the face of scientific theory and evidence,” he says.

But Gradisar says he understands the attraction behind a quick fix such as magnesium spray, particularly for tired and frustrated parents.

Instead of reaching for something such as magnesium spray, Gradisar say parents whose children are having sleep difficulties should always seek the advice of a GP, who can refer them to a specialist if needed and help address the root cause of the issue.

“And the other big factor,” Gradisar adds, “is especially when kids get to school age, they start to have an increase in night-time fears and anxieties. And that’s also something that’s going to push sleep away and needs more specialised treatment. Magnesium just doesn’t cut it.”

While he doesn’t see any potential physical harm coming from the use of magnesium spray on children, Gradisar says there is the potential for psychological troubles down the line once the placebo effect wears off.

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